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REVIEW OF LITERATURE
Idli is a fermented breakfast food widely consumed in southern India. It is
prepared from a wet ground mixture of rice and black gram dhal and it is
famous for its soft, spongy texture, desirable sour taste and characteristic
aroma. Cereal grains are considered to be one of the most important sources
of dietary proteins, carbohydrates, vitamins, minerals and fibre for people all
over the world. Fermentation may be the most simple and economical way
of improving the nutritional value, sensory properties and functional
qualities of food. The indigenous fermented food products produced from
different cereal substrates (sometimes mixed with other pulses) fermented
by lactic acid bacteria and yeast are included. Traditional fermented foods
prepared from most common types of cereals (such as rice, wheat, corn or
sorghum) are well known in many parts of the world.
Several aspects such as methods of idli preparation, effect of raw materials,
effect of temperature and biochemical changes also plays an important role
in deciding the body and textural properties of idli. Therefore, the present
investigation was evaluated the suitability of whey protein concentrate
(WPC) in preparing idli and its effect on some physico-chemical and
sensory characteristics of idli. The relevant information has been reviewed
under the following broad heading:
2.1 Production and properties of idli
2.2 Production and properties of whey protein concentrate (WPC)
2.3 Microbiological quality of idli
2.4 Health benefits of whey protein concentrate (WPC)
2.5 Uses of whey protein concentrate (WPC)
2.6 Nutritional aspects of whey protein concentrate (WPC)
2.7 Cereal based fermented foods
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Production and properties of idli
2.1.1 Idli
Desikachar et al., (1993) stated that an increase in non-protein nitrogen and
a decrease in reducing sugars have been observed during fermentation of idli
batters, the batters are usually prepared by soaking rice (Oryza sativum) and
decuticled black gram (Phaseolus mungo) dhal in water, grinding them
separately, mixing and allowing the mixture to ferment overnight. Both
titratable acidity and the volume of the batter increase as a result of
fermentation and have been used as criteria for judging the progress of
fermentation. A temperature range of 25-30˚C has been found to be optimal
for the fermentation. That both yeasts and bacteria participate in the
fermentation has been shown using penicillin G and chlortetracylin as
selective inhibitors. Acid and gas production have been found to be mostly
dependent on the growth of microbes belonging to the bacterial group.
Radhakrishnamurthy et al., (1993) suggested that black gram has been
reported to play a major role in idli fermentation as a source of micro-
organisms and as a fermenting substrate.
Veen et al., (1993) observed that idli prepared by fermenting a mixture of
soaked and milled parboiled rice and dehulled black gram (Phaseolus
mungo), no appreciable increase in methionine was found after 24 hours of
fermentation, when idli would normally be steamed. The PER and
digestibility in rats were the same as of the unfermented mixture. The
riboflavin content was decreased because the presence of Streptococcus
faecalis in the fermented batter. The presence of pharmacological active
amines such as tyramin was expected but they were not detected.
Reddy and Salunkhe (1993) reported that parboiled rice and black gram
dhal in various proportions are soaked and wet ground separately with added
water to yield a batter of desired consistency. A small quantity of salt is
added and allowed for fermentation overnight during which time
23
Leuconostoc mesenteroides and Streptococcus faecalis, naturally present on
the grains/ legumes/ utensils grow rapidly out- numbering the initial
contaminants and dominating the fermentation. The organisms produce
lactic acid and carbon dioxide, which make the batter anaerobic and leavens
the product.
Reddy et al., (1993) suggested that idli, a popular fermented breakfast food
consumed in the Indian subcontinent is made mainly from rice and black
gram. It is very popular because of its textural and sensory attributes.
Sathe and Salunke (1993) explored the potential use of white beans (Great
Northern) in idli production instead of black gram. It was reported that white
beans could be successfully substituted for black gram in the production of
idli. During the fermentation insignificant protein hydrolysis and gradual
reduction in total sugars were reported.
Juliano and Sakuraj (1993) suggested that parboiled rice is better suited
than raw rice for producing idli, i.e. it is soft without becoming sticky.
Kaw et al., (1993) revealed that the microbiological quality of the
fermenting batters was not affected by the amylase content of the rice used.
However, it was found that among the sensory quality attributes evaluated,
cohesiveness was found to be correlated with the amylase content of rice
used. Filipino and Indian panels evaluated the quality of the idlis in almost
the same part of the scale except for flavour where in the former seemed to
notice the sour off flavour which were not detected by the latter. Probably,
Indians consider this sour off flavour inherent of idli.
Khetarpaul and Chauhan (1994) stated that natural as well as single,
mixed and sequential pure culture (S. diastaticus, S. cerevisiae, L. brevis and
L. fermentum) fermentations of pearl millet flour for 72 hrs lowered pH and
raised titratable acidity. The fermentation either decreased or did not change
the protein content of pearl millet flour. Natural fermentation increased
whereas pure culture fermentation decreased the fat content. Ash content did
24
not change. Natural fermentation at 20˚C and 25 ˚C increased whereas at
30˚C it decreased the thiamine content of the pearl millet flour. Yeast
fermentation raised the level of thiamine two-to three-fold, while lactobacilli
fermentation lowered it significantly.
Swanson and Swanson (1994) investigated the protein quality in idli
produced using black and white beans and rice. They also concluded that
fermentation does not improve protein quality in idli.
Joseph and Swanson (1994) observed that a fermented steamed idli
prepared from beans (Phaseolus vulgaris) and rice. Feed Efficiency Ratio
(FER), Protein Efficiency Ratio (PER) and relative PER of fermented ‗idli‘
diets were significantly smaller (p 0.05) than the FER, PER and rPER of
unfermented ‗idli‘ diets. The true Digestibility Coefficient (DC) and Net
Protein Utilization (NPU) of fermented ‗idli‘ diets were significantly smaller
(p 0.05) than the DC and NPU of unfermented ‗idli‘ diets. Biological value
(BV) of fermented and unfermented ‗idli‘ diets were similar to the BV of a
casein control diet. They further reported that fermentation does not improve
the protein quality of ‗idli‘ prepared from beans and rice.
Yadav and Khetarpaul (1994) observed that the indigenous fermentation
of coarsely ground dehulled black gram dhal slurry at 25, 30 and 35 ˚C for
12 and 18 h reduced the levels of Phytic acid and polyphenols significantly
(P < 0.05). The unfermented legume batter had high amounts of phytic acid
(1000 mg / 100 g) and polyphenols (998 mg / 100 g) and these were reduced
to almost half in the product fermented at 35 ˚C for 18 hrs. In vitro
digestibility of starch and protein improved significantly (P < 0.05) with
increases in the temperatures and period of fermentation. A significant (P <
0.01) and negative correlation found between the in vitro digestibility and
the anti- nutrient further strengthens.
Murthy et al., (1994) has developed an automatic idli making unit that
produces 1200 idlis per hour. The unit consists of automatic idli batter
25
depositor, a special idli pan conveyor, steam chamber and idli scooping
system.
Joseph (1994) suggested that fermented foods prepared from cereals and
legumes are an important part of the human diet in Southeast Asia and parts
of East Africa. The popularity of legume based fermented foods is due to
desirable changes including texture and organoleptic characteristics.
Improvement in digestibility and enhancement of keeping quality, partial or
complete elimination of anti-nutritional factors or natural toxins, increased
nutritive value, and reduced cooking time.
Murthy and Rao (1997) observed that the thermal diffusivity (α) of idli
batter was determined experimentally assuming infinite slab geometry under
transient heat transfer conditions. The value α of batter determined using
batch (1.38 × 10 -7 m2 s -1) and continuous (1.1 × 10 -7 m2 s -1) idli steaming
units were compared with the value obtained using Riedel‘s equation (1.42 ×
10 -7 m2 s -1) and Martens equation (1.1 × 10 -7 m2 s -1).
Nagaraju and Manohar (2000) observed that idli fermentation was carried
out in the conventional way in a batter having rice to black gram in the ratio
of 2:1, 3:1 and 4:1 at room temperature. The rheology of the product was
assessed using a Brookfield viscometer having disc spindles. Yield stress
values were in the range of 13- 43 Pa and reached a maximum value at 7 hrs
of fermentation. Flow behaviour includes were in the range 0.287- 0.605.
Flow behaviour indices at 23 hrs were significantly lower than those at Oh.
Consistency index values, at any fermentation time, increased as the rice to
black gram ratio increased. Mean particle size ranged from 500 to 600 µm
and there was no definite trend noticed with respect to time of fermentation
and rice to black gram ratio. There was a steep change in volume increase
after 4 h fermentation.
Agarwal et al., (2000) reported that the predominant fermentation
microflora comprises lactic acid bacteria and yeast and causes an
26
improvement in the nutritional, textural and flavour characteristics of the
final product. The flavour profile of idli batter prepared with initial levels of
2 × 104 c.f.u. g -1 of Candida versatilis CFR 505 and 2 × 101 c.f.u. g -1 of
Pediococcus pentosaceus CFR 2123 in 500 g idli batter, packed in polyester
polylaminate pouches and stored at 30 ± 2 ˚C was periodically analysed by
GC-MS. The desirable flavour compounds such as ketones, diols and acids
were found to be present upto 8 days of storage, whereas undesirable
flavours like sulphurous and oxazolidone compounds, ethanone and thiazole
appeared in the batter subsequent to 6 days of storage. They further observed
that the flavour profile of traditional fermented foods can be a reliable
qualitative and quantitative parameter.
Teniola and Odunfa (2001) suggested that idli is a low calorie, starchy and
nutritious food, which is consumed as breakfast or snack. Steamed idli
contains about 3.4% protein, 20.3% carbohydrate and 70% moisture.
Nisha et al., (2005) studied that the stabilization of the idli batter at room
temperature (28- 30 ˚C) and refrigerated storage (4- 8 ˚C) by using various
hydrocolloids and some surface active agents. The batter was evaluated in
terms of percentage decrease in volume and percent whey separation. While
hydrocolloids gave good stabilization, surface active agents failed to
stabilize the batter although they reduced whey separation. Among the
various hydrocolloids. 0.1% guar gave best batter stabilization and idlis
made there from after 10 days of room temperature and 30 days of
refrigerated storage of batter were found to be of acceptable quality.
Chandini et al., (2005) studied that the effect of varietal differences and
polishing of rice on quality parameters of idli. Two varieties of raw rice,
―Jaya‖ and ―Minilong,‖ and one variety of parboiled rice ―Ponni‖ with two
degrees of polishing (high and low) were selected. Emulsification capacity
ranged from 102 to 110 mL/ 100 g and foam capacities at different pH range
were similar. Rice with a lesser degree of polishing fermented better with
higher batter volume and microbial count, lesser shear value and gave softer
27
idlis. Sensory analysis revealed that idlis prepared with low-polish rice
scored significantly lower for appearance and color quality compared with
products prepared with high-polish rice. Further concluded that the quality
characteristics of idli were influenced by the variety of rice and the degree of
polishing, but the two types of black gram used, whole and split, had no
effect.
Steinkraus (2005) suggested that the traditional fermented foods contain
high nutritive value and developed a diversity of flavours, aromas and
textures in food substrates.
Sharma and Ali (2006) suggested that replacing rice with kodo in idli had
no deleterious effect on the nutritive value but enhancement of protein, fat,
calcium, phosphorus and fibre. This kodo idli is found to be acceptable,
palatable and nutritious.
Lyer and Ananthanarayan (2008) studied that the fermentation time of the
batter varies from 14 to 24 hrs with overnight fermentation being the most
frequent time interval. Reduction in the fermentation time of the idli batter is
of great commercial significance for large scale idli production and this can
be potentially achieved by addition of enzymes externally. They further
concluded that the possibility of expediting the idli batter fermentation
process by adding an exogenous source of α- amylase enzyme. 5, 15 and 25
U per 100 g batter of amylase were added to the idli batter which was
allowed to ferment. Different parameters were monitored and sensory
attributes were also studied and compared with that of the control set. The
fermentation time was reduced from a conventional 14 h to 8 h and the
sensory attributes of the final product were also successfully maintained.
Susheelamma et al., (2007) studied that greater increase in hydration
capacity of black gram dhal was observed during 5-15 min of soaking, a
gradual increase up to 90 min. Apparent viscosity of batter showed 100%
increase up to 90 min and less than 20% increase beyond 120 min and shear-
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thinning nature of batter indicated that they were pseudo- plastic in nature.
Yield stress and consistency index showed greater changes after 90 min.
Compared with the addition of native rice flour, incorporation of flaked rice
flour and expanded rice flour into black gram batter significantly increased
the cold paste viscosity of the batter, probably because of their greater
water- holding capacity, compared with that from native rice.
Reddy et al., (2007) suggested that the increase of methionine content
during idli fermentation by which path way methionine is synthesized and
identification and isolation of microorganisms responsible for methionine
production or synthesis.
Balasubramanian and Viswanathan (2007) studied that the blend ratio
(66% parboiled rice (Oryza sativa): 33% decorticated black gram
(Phaseolus Mungo Roxb) was fermented for 12 hrs and the batter was steam
cooked for 10 min. Texture profile analysis (TPA) test was performed for
idli, making cylinder samples (13.5 mm diameter, 10 mm long) of idli. In
Pearson correlation matrix, majority of the parameters were positively
correlated at p<0.01 and p<0.05. The firmness value positively correlated
with gumminess and chewiness, which depicts the soft nature of idli.
Resilience is not correlated with other textural parameters. From principle
component analysis (PCA), the first and second principle component,
describe 42.5 and 27.2% of the variance, respectively in the TPA
parameters. The first principle component is highly positively correlated
with gumminess, chewiness and cohesiveness. The second principle
component is positively correlated with firmness and negatively correlated
with springiness. Resilience contributed very weakly to both these principle
components. Based on the results of PCA, the firmness is the prime factor to
illustrate idli texture followed by chewiness, gumminess, cohesiveness and
springiness.
Varnashree et al., (2008) observed that idli prepared by ragi (R), ragi flour
(RF), parboiled rice (PR), black gram dhal (B) and black gram dhal flour
29
(BF) were processed differently and used in different ratios to prepare four
variations of idli [RPRB (1.5:1.5:1), RB (3:1), RFB (3:1) and RFBF (3:1)].
The degree of gelatinization was found to be higher in idlis prepared with
whole ragi and black gram dhal. The water absorption capacity of black
gram dhal was higher and hence soft textured idlis were obtained. They
further reported that whole ragi could be used to replace rice in the
preparation of idli which enhances the nutritional quality without
considerable effect on the quality parameters of idli.
Kanchana et al., (2008) reported that idli was dried by microwave drying
(MD), vacuum assisted MD and hot air drying. Moisture, bulk density, water
activity (aw) and instrumental colour value. Instrumental texture quality was
also studied in the fresh and rehydrated idli. Moisture content of dehydrated
idli ranged between 6.7 and 9.4% and the water activity (aw) was between
0.166 and 0.441. Low power density and low temperature dehydrated idli
was acceptable. Rehydration of idli was better in hot air oven drying
followed by vacuum assisted MD and domestic MD.
Sridevi et al., (2010) studied that idli batter samples were prepared using
lactic starter cultures like Pediococcus pentosaceus (Pp), Enterococcus
faecium MTCC 5153 (Ef), Ent. Faecium (IB2 Ef - IB2), individually, along
with the yeast culture, Candida versatilis (Cv). Idli batter prepared using Ef
and Ef- IB2 cultures gave better results, when evaluated for the rise in batter
volume (80 ml), level of CO2 production (23.8%), titratable acidity 2.4-3.5%
(lactic acid) and pH 4.3-4.4. Storage stability of batter made with selected
starter cultures was determined by analyzing the idlis prepared using the
batter stored for 1 and 5 days for texture, nutrient composition and sensory
quality. They further reported that the idlis of different combination of
cultures, whereas these results are better than that of the idlis made using
naturally fermented idli batter.
Nazni and Shalini (2010) stated that the pearl millet can be used in idli
preparation instead of rice. Replacing rice with pearl millet had good impact
30
on the nutritive value by increasing the protein, fat, fibre, calcium and iron
content in the developed idlis. Thus pearl millet idli is found to be
acceptable, palatable and nutritious.
Rekha and Vijayalakshmi (2011) studied that to reduce the natural
fermentation period of ‗idli‘ from the conventional 14 h to 10 h by adding
underutilized okara for the preparation of ‗idli‘. Black gram was partially
substituted with soy residue okara in the ratio of (1:1). After 14 h of natural
fermentation, the pH and total acidity of control ‗idli‘ batter was 4.51 and
0.64% and that of okara fortified ‗idli‘ batter was 4.53 and 0.43%. The
amount of CO2 released by the control and okara fortified batter was 19.7%
and 33.6%. The viable count of yeast and mould, lactics and mesophilic
bacteria in control and okara batter increased with time reaching 9.00 &
10.34, 8.66 & 7.69 and 8.65 & 9.47 log10 cfu/g respectively at the end of 10
hrs of natural fermentation. Okara fortified ‗idli‘ was soft and spongy
compared to control ‗idli‘.
Ghosh and Chattopadhyay (2011) stated that idli batter is prepared by
soaking polished parboiled rice and decorticated black gram for 4 h at 30 ± 1
˚C in water. The soaked mass was ground using a grinder with adequate
amount of water. The blend ratios of 2:1, 3:1 and 4:1 (w/w) batter were
allowed for fermentation for different periods with the addition of 2% (w/w)
of salt. The rheology of the product was assessed using a Brookfield
Viscometer having disc spindles. Shear stress values were in the range of
0.22 and 4 Pa and reached a maximum value at 7 h of fermentation. The
density, pH and percentage total acidity of batter during fermentation for
different blend ratios ranged between 0.93 and 0.59 gm cm-3, 4.21 and 5.9
and 0.44 and 0.91% respectively. During fermentation, maximum
production of riboflavin and thiamine were found to be 0.76 mg/100 gm and
0.73 mg/ 100 in 3:1 blend ratio of idli batter and the folic acid content was
found to be at a maximum of 0.75 mg/ 100 gm of idli batter after 10 h of
31
fermentation. Digestibility in terms of amino N2 content was analysed by
formal titration.
Aachary et al., (2011) studied that the use of Xylooligosaccharides (XOS)
as a prebiotic in idli, a cereal/ legume based fermented cake and its effect on
texture, fermentation and sensory characteristics was investigated. Idli batter
was fermented with different concentrations of XOS (0, 0.2, 0.4 and 0.6%
w/v) for 4 – 18 hrs conventionally. The addition of XOS markedly increased
lactic acid bacteria number (9.88 ± 0.08 log cfu g -1) which resulted in rapid
reduction in pH (4.61 ± 0.03) and specific gravity after 6 h of fermentation
when compared to conventional batter fermentation for 18 h without XOS
(9.46 ± 0.06 log cfu g -1). Instrumental (colour and texture) and sensory
evaluation indicated that the optimum conditions were 0.4% XOS and 6 h
fermentation. Idlis with XOS had higher moisture content and a softer
texture. Addition of XOS benefits both fermentation and idli quality.
2.1.2 Semolina
Erbas et al., (2004) observed that moisture adsorption isotherms of
semolina (from hard wheat) and farina (from soft wheat) were determined at
20, 35, 50 and 60 ˚C using the isopiestic method. The adsorbed moisture
content significantly affected product type, temperature and water activity.
Moisture up-take accelerated about 0.75 water activity. Henderson, Halsey
and GAB equations were found to be the most suitable model to describe the
isothermal water sorption of semolina and farina at 0.1-0.9 water activity
range. Monolayer moisture content (m0) for two products were calculated
from BET and GAB equations. The m0 values of both models decreased with
increasing temperature. Adsorption isosteric heat (Qs) decreased, the
maximum heat of adsorption was obtained in the moisture content 6-7% and
was higher for semolina (15.2 kJ / mol) than farina (14.34 kJ / mol). The Qs
value quickly decreased with increase in moisture content to approximately
15% and then was plateau on axis of moisture content. Semolina and farina
must be storage below 75% relative humidity at 20 ˚C prevents caking and
32
deterioration because moisture sorption acceleration was increased after
0.75aw. The moisture content of the products in this storage conditions could
be approximately 12.5%.
2.1.3 Functional properties of semolina
Reddy and Yenagi (1997) observed that the semolina yield of dicoccum
wheat varieties is comparable to durum and traditional products of dicoccum
wheat have better taste, flavour and suited for preparation of Godihuggi,
Gulladaki laddu and roasted madeli.
Reddy et al., (1998) observed that Dicoccum (Triticum dicoccum) is a class
of wheat grown in India and represents a small percentage of total wheat
production. It is a quality wheat and also known as ‗Jave‘ wheat and used
for preparation of semolina for use in various Indian traditional products.
Patil et al., (2003) reported that swelling power and percent solubility of
semolina of different grades of dicoccum wheat was lower than durum and
bread wheat varieties. Dense products of ‗very coarse‘ and ‗coarse‘ semolina
of dicoccum varieties are highly acceptable and are more nutritious. It was
also found that ‗DWR-2006‘ durum variety and high swelling and solubility
index with good pasting characters.
Ranhotra (2006) suggested that wide varieties of products are prepared
from milled fractions of wheat and is well documented that soft wheat is
used for preparation of cakes, biscuits and pastry. Hard wheat is used for
preparation of bread and chapatti and durum wheat is used for preparation of
dense breakfast and pasta products.
2.2 Production and properties of whey protein concentrate (WPC)
Whey protein concentrate (WPC), a co- product of cheese making and
casein manufacture, represent a rich and heterogeneous mixture of proteins
with a broad range of nutritional and functional properties. Functional
properties of whey proteins in foods include solubility, dispersibility, heat
33
stability, formation (gels and edible films) and surface activity (emulsions
and foams).
Berlin et al., (1973) studied that measurements of the heat of fusion of free
water in concentrated solutions of purified whey proteins showed that .5 g
water/g whey protein would not freeze at –40 C. This water was defined as
bound. Total bound water in protein solutions containing lactose and salts
varied between .5 and 1.2 g water/g solids, with unfreezable water
increasing as the concentrations of lactose and salts were increased. Bound
water values observed with several whey protein products agreed with
values computed from data both for high and low molecular weight fractions
of these products. Thermal denaturation did not cause significant changes in
water binding.
Forsum (1974) reported that nutritional evaluation of whey protein
concentrates and whey protein fractions was performed by Protein
Efficiency Ratio and Net Protein Utilization assays as well as by
calculations of chemical scores. The whey protein concentrates were
industrially produced by gel filtration and ultrafiltration and were
fractionated further by large-scale gel filtration. Nutritional values of the two
concentrates were similar and high. Whey protein fractions containing α
lactalbumin had high Protein Efficiency Ratio and Net Protein Utilization
values while fractions containing β-lactoglobulin had high Net Protein
Utilization values but only moderate Protein Efficiency Ratio values.
Mcdonough et al., (1974) stated that protein concentrates were susceptible
to heat; normal pasteurization temperatures resulted in approximately 20%
denaturation. Whey protein exhibited excellent water retention. Addition of
1.5% protein to skim milk followed by heating formed a custard-like gel
with sufficient body to stand alone without leakage. Approximately twice as
much egg albumin was required to achieve comparable results. Whipping
properties were very good when butterfat content was less than 2%.
34
Excellent stable whips could be produced by a combination of heat and pH
adjustment.
Forsum et al., (1974) observed that large-scale fractionation of whey
protein concentrates was performed by pre-paratory gel filtration. A
prototype of a stacked column, KS 450, packed with Sephadex® G-75 and
equilibrated with .1 M phosphate buffer pH 6.3 was utilized. Both an
ultrafiltered and a gel-filtered whey protein concentrate were fractionated
into three different fractions, the protein composition of which was
evaluated by electrophoresis, amino acid analyses, and casein estimations.
The nitrogen distribution between the different fractions was also analyzed.
By large-scale gel filtration, β-lactoglobulin of high purity and preparations
rich in α-lactalbumin could be obtained in large quantities.
Mcdonough et al., (1976) stated that WPC were prepared from cheese whey
by ultrafiltration and were evaluated as a milk extender. Ash values
generally were lowered by ultrafiltration averaging 10.5% for cottage cheese
whey and 7.5% for its corresponding concentrate. Feeding trials of rats
indicated bioavailability of the dried concentrates was higher than that of
both casein and skim-milk powder. Addition of dried concentrate to nonfat
dry milk as a 40% blend raised the protein efficiency ratio of the nonfat dry
milk from 2.51 to 2.83. Sensory evaluation indicated that up to 40%
concentrate from sweet whey or 20% from acid whey can be blended with
skim milk without adversely affecting organoleptic quality.
Jost et al., (1976) observed that the casein digestion test indicated that
neutral or alkaline proteases were absent. Hemoglobin digestion at acidic pH
indicates trace amounts of acidic proteases, most likely derived from the
rennet. No changes were detected by gel filtration on Sephadex G-75 and by
polyacrylamide gel electrophoresis with sodium dodecyl sulphate, in the
protein pattern upon aging wheys for a few days. Whey proteins were
incubated at pH 6.2 and 4.5 with high concentrations of commercial rennet.
α-Lactalbumin and β-Lactoglobulin were not affected. In contrast, at pH 4.5
35
serum albumin was degraded extensively, and the H-chain of the
immunoglobulins underwent limited digestion.
Hidalgo and Gamper (1977) reported that rennet whey protein concentrates
have excellent nutritional properties, but their use in fluid food systems is
impaired by the poor heat stability of the protein. Heating whey protein
concentrated solutions at neutral pH caused up to 70% loses in solubility. In
the absence of added calcium, protein coagulation occurred near the iso-
electric zone whereas in the presence of .03 M calcium chloride, similar
protein coagulation occurred in the whole pH range (pH 2 to pH 12). Tryptic
hydrolysis of the protein increased the heat stability of whey protein
concentrates considerably.
Modler and Emmons (1977) stated that WPC prepared by heating at pH
2.5 to 3.0 had a minimum solubility of 78%. This was reduced to 51% when
the pH during heating was 3.5. Although addition of iron to whole whey
increased protein recovery, solubility was reduced. Concentrating whey
prior to heating greatly increased protein recovery but substantially reduced
solubility. The viscosity of spray-dried samples of acid-heat WPC
reconstituted to 33% solids ranged from 4,000 to 36,800 centipoise while
commercial samples had viscosities of 400 to 1,840 centipoise.
Experimental samples of WPC gelled at protein concentrations of 2, 4, 6,
and 8% heating at 95 C for 20 min. All experimental samples had excellent
color stability while commercial samples darkened upon heating.
Thompson and Reyes (1980) reported that heat coagulated cheese WPC
was modified by reaction with succinic anhydride at pH 8 followed by
isoelectric precipitation, neutralization, and freeze drying. All functional
properties except whippability were improved. Succinylated WPC dispersed
readily as highly swollen particles with high viscosity. It has high
emulsifying capacity and can form stable emulsions at 1% usage. Gel
filtration indicates extensive unfolding of the protein after succinylation.
36
Succinylation increased the protein content of the WPC with little loss in
biological value and yield.
Phillips (1981) stated that proteins are among the most widely used natural
emulsifiers because they can decrease the interfacial tension and form a
protective layer around oil/ fat globules in emulsions.
Cheftel and Lorient (1982) stated that whey protein concentrate (WPC)
represent an important and valuable source of ingredients due to their
effective nutritional, sensory and functional properties such as water
absorption, gel formation, emulsification and foaming.
Chan (1983) reported that accelerated storage tests of WPC were carried out
to characterize changes of the proteins that may affect its nutritional quality
or functional properites. After 42 days at 37°C and 75% relative humidity,
pH 4.6 soluble protein decreased only slightly (14% loss), and there were no
significant changes of sulfhydryl or disulfide content, Hydroxyethylfurfural
increased dramatically (17 to 192 μmoles/100 WPC). ―Free‖ lactose, and
total, dinitrobenzenesulfonate-available and pepsin-pancreatin-digestible
lysine contents also decreased (17, 34, 57, and 72% losses).
Melachouris (1984) observed that the technical aspects are whey source,
whey pre-treatment, ultrafiltration membrane performance, characterization
of liquid process streams, characterization of whey protein concentrates,
application of whey protein concentrates (WPC) and effluent stream
utilization. Functional whey protein concentrates (WPC) produced under
strict quality control conditions could find a growing market and could be
used as key ingredients in development of new food products.
Dewit and Klarenbeek (1984) observed that mild heat treatments up to
60°C may affect reversibly the solubility and foaming properties of whey
proteins. Conformational changes, as reflected by differential scanning
calorimetry and observed above 60°C for α-lactalbumin and near 80 and
140°C for β-lactoglobulin, however, exert more serious effects on the
37
functional properties of whey proteins. Modifications of cystine-residues in
the polypeptide chain are detected by amino acid analysis upon heat
treatments above 100°C under identical heating conditions as used for
differential scanning calorimetry.
Mangino (1984) reported that many of the desirable attributes of foods may
be directly or indirectly related to the functionality of their protein
components. In which food proteins interact with other food components as
well as with themselves determines their functionality. The protein structure
relate to physical requirements necessary for water binding, gelation,
emulsification, and foam formation. Factors that affect these functional
properties are related to changes of protein structure. The nature of
interactions required for optimal functionality are related to conditions that
alter protein structure in such a way as to encourage occurrence of these
interactions.
Kester and Richardson (1984) stated that Modification of whey proteins to
enhance or alter their functional properties may increase food applications.
Whey protein modification can be accomplished by chemical, enzymatic, or
physical techniques.
Schmidt et al., (1984) reported that WPC preparations, prepared by
electrodialysis, ultrafiltration, reverse osmosis, gel filtration, and reagent
complexation, are highly variable in their composition and functionality.
Factors affecting the functional properties of WPC include: whey source and
composition, cheese or casein manufacturing conditions, heat treatment
conditions, fractionation and isolation conditions, storage conditions, overall
sanitation conditions, and techniques used for functionality evaluation.
Process modifications such as selective heat treatment, selective
demineralization or ion exchange, and preteolytic enzyme hydrolysis may be
used to alter these functional properties for a desired use application.
38
Matthews (1984) stated that whey protein properties that have been
exploited commercially include: molecular size differences (ultrafiltration,
gel filtration), insolubility of protein at high temperature, charge
characteristics demineralization, protein removal by ion exchange),
aggregation by polyphosphates, and crystallization of lactose. Numerous
other isolation procedures have been investigated. Chemical, physical, and
functional characteristics vary according to method of manufacture. Capital
costs for most of these processes are high. As yields are characteristically
low, careful economic analysis is necessary.
Harper (1984) reported that the procedures for development of model food
systems for evaluation of functionality of whey protein concentrates as an
alternative to traditional functionality testing in simple systems. The
approach is illustrated for two model systems, a coffee whitener and a
whipped topping. Results indicate factors that must be considered in model
development. In the coffee whitener, protein type must be considered, and
the same model may not be applicable to different types of proteins.
Kilara (1985) stated that the enzymatic hydrolysis of proteins includes:
enzyme specificity, extent of protein denaturation, substrate/ enzyme ratio,
pH, ionic strength, temperature and presence or absence of inhibitory
substances.
Mulvihill and Donovan (1987) stated that whey protein isolate (WPI) is
widely used because of its unique nutritional, physico- chemical and a
functional property of WPI is their ability to form gels. Gelation is
considered to be a result of partial unfolding followed by aggregation.
Garrett et al., (1988) reported that the thermal coagulation of unfractionated
whey proteins was inhibited by various sugars. The diasaccharides, sucrose
and lactose were most effective and the amino sugar, glucosamine, least
effective in this respect. Ultraviolet absorption and light- scattering
measurements on the thermal denaturation and coagulation of both
39
unfractionated and individual whey proteins (α- lactalbumin, β-
lactoglobulin and bovin serum albumin) showed that sucrose promotes the
denaturation of these proteins but inhibits their subsequent coagulation.
Hsu and Fennema (1989) observed that various functional properties
(protein solubility, foam stability, emulsifying capability) and development
of browning of dry WPC containing 52% protein were monitored during 6
month at temperatures ranging from −40 to 40°C and water activities
ranging from .15 to .41. To achieve good retention of the initial attributes of
WPC during 6-mo storage, the temperature should be no higher than 20°C
and the water activity should not exceed about .2.
Sienkiewicz and Riedel (1990) studied that the water binding capacity of
WPC is influenced by protein concentration, mineral content and the extent
of heating during manufacture.
Patel and Kilara (1990) studied that the concentrates were prepared from
cheese whey obtained from skim milk, whole milk, and buttermilk-enriched
skim milk. In comparison with the other whey protein concentrates,
concentrates prepared from skim milk whey had lower surface
hydrophobicity and concentrates prepared from buttermilk-enriched skim
milk whey had lower solubility. Whey protein concentrates prepared from
whole milk whey had poor foaming and emulsifying properties. In general,
free fat and bound fat were negatively related with foaming and emulsifying
properties, whereas, ash, calcium, and denaturation enthalpy were positively
related with foaming and emulsifying properties.
Patel et al., (1990) observed that the samples were prepared from three milk
viz. skim milk, whole milk, and skim milk enriched with buttermilk. The
concentrates from skim milk were lower in all fat components and higher in
proteins, except for the membrane-associated protein. The buttermilk-
enriched samples had the most membrane-associated components. The
concentrates from whole milk and buttermilk-enriched, skim milk were
40
similar in protein composition, except for membrane-associated protein. The
whole milk samples had the highest concentrations of total and free fat
components. Lactose content and mineral composition were similar for the
three types of concentrates. Thermal properties and denaturation kinetics
were examined by differential scanning calorimetry.
Wit (1990) suggested that the functional properties of whey proteins are
often impaired by inevitable heat treatments during processing of whey
protein products and preservation of food products. The effect of heat
treatments between 70 and 90°C is analyzed in terms of the kinetics of whey
protein unfolding and aggregation. The results reveal that thermal
denaturation of whey proteins during industrial heating processes is
predictable. An important determinant for functional properties is the salt
composition of whey protein products during heat treatments at temperatures
above 75°C.
Renner and Salam (1991) suggested that whey proteins have higher protein
efficiency ratio, net protein utilization and biological value compared to
casein and any other food proteins. These proteins are considered as the best
quality protein.
Morr and Ha (1991) studied that the chemistry of off- flavour formation in
WPC products in comparison to milk and whey by maillard reaction, lipid
oxidation and riboflavin decomposition during storage and suggests whey
pre-treatment processing technology to improve the flavour stability of
WPC.
Geoffrey and Geoffrey (1991) reported that seasonal changes generally
included a reaction in the α- lactalbumin content of WPC manufactured
during the final three months of lactation, concomitant with a rise in the
level of β- lactoglobumin. These changes contrassed with an increase in the
casein content of WPC prepared during the first 4 month of lactation.
41
Seasonal variation in the relative proportion of the major protein constituents
of WPC has important implications for the dairy industry.
Nagendra et al., (1991) stated that the decrease in the scores above 40%
levels of replacement could be attributed to the formation of large grains
because of incorporation of WPC.
Jayaprakasha (1992) stated that fresh chedder cheese whey was subjected
to fractionation by ultrafiltration plant (Permionics Ltd. Baroda) possessing
polysulphone membrane with 1.8 m2 effective surface area at a temperature
of 50 ˚C and pressure of 100 psi until the retentate reached to a TS content
of 9.0% by processing whey to a volume reduction of about 80 to 85%.
Geoffrey and et al., (1992) reported that transition energy associated with
protein denaturation was reduced for WPC prepared in the final 3 mo of
lactation. This decrease paralleled a similar decrease in α- lactalbumin
content and surface hydrophobicity of the WPC. Other seasonal changes in
the functional properties of WPC prepared in the letter half of lactation. Heat
induced gel firmness was generally higher for WPC manufactured in the
final 3 mo of the lactation cycle, on observation that paralled an increased
proportion of β- lactoglobulin in WPC prepared at that time.
Gauthier et al., (1993) suggested that enzymatic hydrolysis of whey
proteins has the potential to improve solubility, emulsifying and foaming
properties.
Barbut and Foegeding (1993) stated that protein unfolding and aggregation
are particularly sensitive to pH and ionic strength. At low ionic strength
gelation is prevented by electrostatic repulsion between molecules. Addition
of ions after pre- heating of protein dispersions induces gelation.
Kawachi et al., (1993) suggested that whey protein gelation at ambient
temperatures has potential applications in the food industry. It can be used in
42
the production of desserts, dressing, spreads, bakery products, pressed ham
and surimi.
Donald et al., (1993) reported that concentrating milk by ultrafiltration
shortened coagulation time and increased gel firmness. UHT processed milk
did not coagulate when rennet was added. Its 3 × concentrated counterpart
did coagulate although only a weak gel was formed. UHT heating caused the
casein micelles to increase in size with additional protein material adhering
to their surface, especially in the 3 × skim milk heated to 140 ˚C. This
diffuse layer of material around casein micelles was not observed in 3 ×
whole milk. It is suggested that this denatured protein is adsorbed onto the
fat water interfaces during homogenization.
Althouse et al., (1995) suggested that the functional properties of whey
proteins concentrate (WPC) for their effective utilization in the food
products.
Banerjee and Chan (1995) stated the the functional properties of whey
protein concentrate films were compared with those of the films derived
from sodium caseinate, potassium caseinate, calcium caseinate, and whey
protein isolate. Water vapor permeability of simple whey protein concentrate
film was lower than that for films of sodium caseinate, potassium caseinate,
and whey protein isolate. Composite whey protein concentrate film had the
lowest water vapor permeability of all the milk protein films. The ultimate
tensile strengths of simple whey protein concentrate films were similar to
those of caseinate films. Whey protein concentrate films had good water
vapor barrier and mechanical properties that were comparable with those of
films from other commercial milk proteins.
Jayaprakasha et al., (1995) stated that technology for the conservation of
whey solids in the form of whey protein concentrate (WPC) is the best way
to redeem these solids.
43
Turgeon et al., (1996) studied that whey protein concentrate (WPC), a heat-
treated WPC (90 °C, pH 2.5, 10 min) and peptidic fractions obtained by
ultrafiltration of their tryptic and chymotryptic hydrolysates were
incorporated in a salad dressing formulation at 0.5, 1.0 or 1.5% (w/w)
protein. Peptidic fractions obtained from tryptic hydrolysates produced the
most stable salad dressings (over 6 months at the 1.0% and 1.5% protein
level) with rheological properties similar to a commercial mayonnaise. The
most important factors for emulsion stability were the incorporation level
and the nature of peptides.
Regester et al., (1996) stated that it is estimated that 30% of the world‘s
milk production is utilized for cheese preparation, which generates nearly
83,030 million kg of whey.
Vaghela and Kilara (1996) stated that the freeze- dried WPC containing 35
and 75% protein and varying amounts of residual lipids, were manufactured
by pretreating whey with calcium chloride and heat. These and commercial
WPC were subjected to proximate analysis, resulted in WPC that had
significantly lower total lipids and a lower lipids to protein ratio. The
commercial WPC had ratios of lipid to protein that were significantly higher
than all experimental WPC. The pre-treatment significantly increased the
proportions of phospholipid and monoacylglycerol and decreased the
proportion of triacylglycerol.
Mleko and Achremowicz (1996) suggested that the most important
functional properties of whey protein isolates, as a food component is their
ability to form gels. Dispersions of heated whey proteins can form gels when
salt is added before or after heating.
Milena and Douglas (1996) reported that skim milk was heated at
temperature in the range 75-90 ˚C at pH values of 6.8, 6.2 and 5.8. The
amounts of α- lactalbumin and β- lactoglobulin which interacted with the
casein micelles during heat treatment. Both α- lactalbumin and β-
44
lactoglobulin appeared to interact similarly with casein micelles at
temperatures up to 85 ˚C. The amount of whey protein complexed with
micelles increased with time, reaching plateau values that, at the highest
temperature, were comparable with the quantity present in the original skim
milk. In general, faster reaction of the whey proteins with the micelles was
found at lower pH and higher temperatures.
Kinekawa and Kitabatake (1996) reported that β-Lactoglobulin was
purified from WPC by a combination of pepsin treatment and membrane
filtration. Porcine pepsin was added to whey protein (1:200, wt/wt), and the
mixture was then incubated at pH 2.0 and 37°C for 60 min. The protein
fraction was collected by ammonium sulfate precipitation, and the
precipitate was either dialyzed against water using a dialysis membrane (20-
kDa pore size) of filtered using an UF membrane (30-kDa pore size). The β-
LG did not differ from standard β-LG as measured by chromatography.
Hsu and Kolbe (1996) reported that WPC containing 33 or 72% protein
were evaluated as functional ingredients to improve the textural properties of
surimi seafoods made from Pacific whiting. The development of least cost
formulations of these products using nonlinear programming techniques was
used to evaluate the economic viability of WPC. WPC ingredients were
promising because they remained economically competitive with potato
starch and beef plasma protein, which are commonly used as ingredients in
whiting surimi seafoods. Factors affecting the amount of WPC in the least
cost formulations.
Mleko (1997) stated that whey protein gels find a wide range of applications
in forming texture of a new product or mimic the texture of an existing one.
Elofsson et al., (1997) studied that the cold- gelling whey protein powder
was found to consist of large, micron-sized, drying-induced, weak
aggregates consisting of primary disulfidebridged aggregates of 20 – 30 nm
in diameter. In dilute solutions under conditions of large repulsive forces
45
(low ionic strength and pH far from the isoelectric point) the large
aggregates dissolved slowly over many hours. In less good solvents, larger
aggregates remained or were formed.
Nielsen (1997) observed that partial hydrolysis of protein generally
increases the number of polar groups and hydrophobicity, decreases the
molecular weight, alters the globule structure of proteins and exposes
previously buried hydrophobic regions. These changes will alter their
emulsifying properties.
Casper et al., (1999) studied that whey protein concentrates were prepared
from two caprine and one ovine specialty cheese wheys by ultrafiltration-
diafiltration and freeze-drying processes. The WPC were compared with a
bovine WPC prepared by same method. Ovine WPC showed better foam
overrun, foam stability, and gel strength than did bovine and caprine WPC
and both caprine WPC showed better gel strength than did bovine WPC.
Caprine WPC produced from rennet whey, showed better emulsifying
capability at low pH than did both bovine and ovine WPC. Caprine WPC
produced from direct-acidified whey, had less emulsification capability than
bovine WPC produced from rennet whey.
Mleko and foegeding (1999) used two- stage process to obtain whey
protein gels. The first stage was performed at pH 8.0, when whey protein
molecules get polymerized by disulphide bonds and the second stage was
carried out at pH 6.0-7.0, which favour noncovalent bonds.
Jayaprakasha and Brueckner (1999) stated that the production of cheese
nearly 50% of the milk solids are lost through whey, resulting in colossal
losses of nutritious solids. Whey solids are known to carry excellent
nutritional and functional properties.
Keogh and Kennedy (1999) reported that the increasing of homogenisation
pressure, reduced the fat globule diameter and increasing the number of
homogenisation passess reduced the diameter of the largest globules.
46
Increasing fat and salts reduced fat globule diameter stability after 2
homogenisation passes but the reduction in stability was less after 4 passes.
Increasing the lactose: whey protein concentrate (WPC) ratio reduced free
fat and fat globule aggregation after powder reconstitution, but not the
surface fat. The higher level of fat increased the surface fat on powder
particles and the level of oxidation during storage.
Hayes and Nielsen (2000) observed that the plasmin activity in whey
protein products may cause breakdown of food proteins to have desirable or
undesirable effects on food quality. Acid whey protein products had
significantly higher plasmin concentrations then sweet whey. Plasmin
activities associated with acid and sweet whey protein products were both
significant affected by the growth of Pseudomonas fluorescens M 3/6. The
interaction effect between bacterial growth and whey type on plasmin
activity was not significant. Plasmin activity in the reconstituted commercial
WPC (i.e., sweet and acid) varied considerably (16.3 to 330 µg/ g of
protein), but was significantly lower (2.1 to 4.4 µg/ g) of protein in whey
isolates.
Jayaprakasha (2000) suggested that the most promising way could be
inclusion of WPC in traditional food products, as these traditional foods
occupy a very important place in Indian dietary. Several food formulations
have been developed utilizing WPC which impart better physico- chemical
and functional properties, besides improving the nutritional profile of such
products.
Brandsma and Rizvi (2001) stated that optimal cheese manufacturing
parameters were determined to be 80–100 μL rennet kg–1 MF cheesemilk,
coagulation temperature of 32–36 °C, and post-coagulation curd cutting time
of 15 min. As compared with ultrafiltration (UF) retentate cheese
manufacture, cheese made from MF retentates has potential for improved
textural and functional qualities, along with recovery of highly functional
whey proteins (WP) from permeate.
47
Mleko et al., (2002) observed that whey protein gels were obtained at
ambient temperatures from no salt heated dispersions with calcium ions as
an inducing agent. Double heating of whey proteins resulted probably in
extensive unfolding of whey proteins and subsequent formation of polymers/
aggregates. Further increase of calcium concentration caused probably
higher aggregation, which influenced the balance between inter and intra-
molecular forces and affected rheological properties.
Mleko (2002) studied that whey protein polymers/ aggregates were obtained
in a two-stage heating process. Sample were mixed for 5 min at 20,000 rpm
and rheological properties were compared with non sheared dispersions.
Gels prepared from pre sheared dispersions at pH 7.0 and 6.5 characterized
higher storage moduli and lower phase angels. Pre shearing of the
dispersions obtained at pH 6.0 resulted in a weaker gel, probably because of
higher aggregation. Non sheared gels had a higher optical density then pre
sheared gels, which suggests formation of a gel composed of larger
aggregates.
Desrumaux and Marcand (2002) reported that the emulsifier used was
whey protein concentrate (1.5%). The properties of the emulsions were
characterized by laser light scattering (droplet size distribution) and coaxial
cylinders rheometry (rheological behaviour). The protein adsorption fraction
was obtained by a spectrophotometric method using bicinchoninic acid
reagent. No change was revealed by polyacrylamide gel electrophoresis of
the whey protein within the pressure range studied. Microdifferential
scanning calorimetry scans indicated that the changes of the structural and
textural properties may be because of changes in the protein conformation.
Yoshida et al., (2002) stated that edible films, using whey protein as the
structural matrix, were tested for water vapour diffusion properties. Whey
protein films were prepared by dispersing 6.5% whey protein concentrate
(WPC) in distilled water with pH kept at 7.0. Glycerol was the plasticizer
agent. Film slabs (13.5 × 3.5 cm) were put in a chamber at 25 °C and 75%
48
relative humidity, being held in vertical planes for different periods of time.
The mass gain was determined throughout the experiment. Moisture
adsorption by milk whey protein films is well described by a linear diffusion
equation model.
Spiegel and Huss (2002) studied that the effects of pH-value and a
reduction in calcium content on the kinetics of whey protein denaturation
and the aggregation behaviour, under shear in a scraped surface heat
exchanger. Aggregates which are produced under shear between pH 4 and
5.5 reveal a small particle size (<5 μm) irrespective of the lactose content
and the heating temperature. At a reduced calcium concentration the heat-
and shear-treatment resulted in a gritty structure with large rubber-like
particles. These are not to be taken as primary whey protein aggregates but
as fragments of a fine-stranded gel.
Totosaus et al., (2002) reported that protein gelation has been traditionally
achieved by heating, but some physical and chemical processes form protein
gels in an analogous way to heat-induction. A physical means, besides heat,
is high pressure. Chemical means are acidification, enzymatic cross-linking,
and use of salts and urea, causing modifications in protein–protein and
protein–medium interactions. The characteristics of each gel are different
and dependent upon factors like protein concentration, degree of
denaturation caused by pH, temperature, ionic strength and/or pressure.
Downey (2002) stated that freezing and thawing have been shown to
adversely affect the centrifugal drip loss and maximum resistance to
penetration of cooked, puréed vegetables (potatoes, carrots and turnips).
Amelioration of these effects has been investigated through the addition of
cryoprotectants (xanthan gum, guar gum, pectin, carrageenan, sodium
caseinate, WPC). In general, gums (xanthan and guar) proved most effective
in reducing drip losses although carrageenan and pectin exhibited some
ability in this regard. Dairy powders produced no effect on drip loss but did
alter maximum resistance values after thawing.
49
Foegeding et al., (2002) suggested that whey protein ingredients are used
for a variety of functional applications in the food industry. Each application
requires one or several functional properties such as gelation, thermal
stability, foam formation or emulsification. Whey protein ingredients can be
designed for enhanced functional properties by altering the protein and non-
protein composition, and/or modifying the proteins. Modifications of whey
proteins based on enzymatic hydrolysis or heat-induced polymerization have
a broad potential for designing functionality for specific applications.
Briczinski and Robert (2002) observed that whey was ultrafiltered and
diafiltered to remove lactose and salt, freeze- dried and milled to a powder.
Unfermented hydrolyzed and unhydrolyzed whey controls were processed in
the same manner. The EPS-WPC ingredients contained approximately 72%
protein and 6% EPS but they exhibited low protein solubility (65%, pH 7.0,
pH 3.0).
Yoshida et al., (2003) stated that the macroscopic aspects of moisture
transmission in whey protein films were determined by measuring water
vapour adsorption. A theoretical model was constructed in which two kinds
of water vapour fluxes were considered: one originating from diffusion,
whilst the other was a flux due to the gravitation drift of moisture. The
comparison of theoretical and experimental results showed that only the
diffusion process was present.
Bailey (2003) stated that the milk protein concentrates are used in the United
States in many different products, including the starter culture of cheese, or
in non standard cheeses such as baker's cheese, ricotta, Feta and Hispanic
cheese, processed cheese foods, and nutritional products. One of the difficult
aspects of trying to assess the impact of MPC imports on the US dairy
industry is to quantify the protein content of these imports. The protein
content of MPC imports typically ranges from 40 to 88%.
50
Piyasena and Chambers (2003) studied that the influence of whey protein
dispersions (WPDs) on syneresis of renneted curd. Curd produced from milk
with added WPDs contained less protein and less fat than that produced
from raw milk. These findings reveal the importance of substrate pH in
combination with homogenization of added protein dispersions from whey
when utilized by cheese producers to optimize cheese yield and
composition.
Bals and Kulozik (2003) observed that the effect of the thermal
denaturation of whey proteins on the formation, stability and structure of
their respective foams. A membrane foaming apparatus, which is a very
gentle foaming method was used to produce the foams. It was shown that the
denaturation of the β-lactoglobulin, the main component in whey protein
isolate, strongly improves the foam stability. At a denaturation degree
>70%, it is possible to reduce drainage to a large extent. The image analysis
demonstrated that higher levels of denaturation of the proteins and thus
higher viscosities of the protein solution produced coarser foam textures
with larger bubbles. The incorporation of the bubbles was more difficult
when the viscosity of the continuous phase was high.
Miralles et al., (2003) capillary electrophoresis (CE) was used to determine
the whey protein to total protein ratio in raw and UHT milk samples with
different degrees of proteolysis caused by storage. In UHT milks, the
overestimation of the whey protein to total protein ratio took place after 30
or 60 d of storage. However, the ratios αS1-CN/β-CN and αs1-CN/κ-CN
permitted detection of the samples of raw or UHT milk with degraded
proteins.
Pasin and Miller (2004) suggested that whey protein concentrate (WPC)
are dairy ingredients that are highly nutritious with a protein efficiency ratio
of 3.6 and a protein digestibility corrected amino acid score of 1.14 as
against 1.5 and 0.25 for wheat proteins.
51
Wroblewska et al., (2004) reported that commercial whey protein
concentrate (WPC) was hydrolysed with either Alcalase 2.4 FG (Novo
Nordisk), or papain (Sigma) (in one-step process) or with two enzymes (in
two-step process) to determine the changes in the immunoreactivity of α-
lactalbumin and β-lactoglobulin. The ‗two-step‘ process was observed to be
the most effective however allergenic epitopes were still present, as it was
found by enzyme- linked immunosorbent assay (ELISA) with anti-α-la and
anti-β-lg antibodies. The addition of papain as the second enzyme in the
hydrolysis process contributed to the improvement of the sensory properties
of WPC hydrolysate as compared with the Alcalase hydrolysate. Alcalase-
papain partially hydrolysated WPC can be found a promising base for
production of the tolerogenic formula.
Resch et al., (2004) studied that the freeze-dried and spray-dried derivatized
WPC powders, along with polysaccharide thickeners, were reconstituted in
water and evaluated by using a range of rheological studies. The effects of
temperature, concentration, and shear on viscosity as well as the mechanical
spectra were assessed to characterize the ability of the powders to function
in food systems. Rheological characterization revealed the modified
derivatization procedure yielded an ingredient having the same cold-set
thickening and gelling ability as the original derivatized powder. The
modified whey proteins were also able to achieve, at higher usage levels,
textural properties similar to several polysaccharide thickeners.
Christiausen et al., (2004) observed on the stability of WPC and β-LG
dressings, while hydrolysate dressings showed reduced stability, except for
the combination of low pH (4.0), high protein (4%) and fat content (30%).
This dressing was highly stable at high processing temperature. The
microstructure of WPC dressing showed homogenous, non-aggregated
structure in contrast to hydrolysate and β-LG dressing, which showed highly
ordered, aggregated structure which supports the rheological measurements
for gel formation.
52
Veith and Reynolds (2004) observed that process for the production of a
whey protein concentrate (WPC) with high gel strength and water-holding
capacity from cheese whey. To maintain whey protein solubility, it is
necessary to minimize heat exposure of the whey during pre-treatment and
processing. The presence of the caseinomacropeptide (CMP) in the WPC
was found to be detrimental to gel strength and water-holding capacity. All
of the commercial WPC that produced high-strength gels exhibited ionic
compositions that were consistent with acidic processing to remove divalent
cations with subsequent neutralization with sodium hydroxide.
Zafer et al., (2005) observed that the fermentation of whey by
Kluyveromyces marxianus strain MTCC 1288 using varying lactose
concentrations at constant temperature and pH. The increase in substrate
concentration up to a certain limit was accompanied by an increase in
ethanol formation. An increase in lactose concentration to 100 g L−1 led to a
drastic decrease in product formation and substrate utilization. The
maximum ethanol yield was obtained with an initial lactose concentration of
50 g L−1. A method of batch kinetics was utilized to formulate a
mathematical model using substrate and product inhibition constants.
Reskin et al., (2006) reported that fat globule aggregation and adsorbed
protein content in whipped frozen emulsions were determined after
application of thawing, dilution or centrifugation. Micrographs indicated that
in aerated products, partial replacement of native whey proteins by pre-
denatured whey proteins or casein introduced (i) more homogeneity in air
bubble size, (ii) more attachment of fat globules to their air serum interface,
(iii) fat globules in the continuous matrix that were in closer contact with
each other. These differences in the microstructures of whipped frozen
emulsions were attributed to differing surface heterogeneity of adsorbed
protein particles of fat globule interfaces.
Anema et al., (2006) result revealed that the effect of storage time and
temperature on the solubility of milk protein concentrate (MPC85) using
53
solubility tests, gel electrophoresis and mass spectrometry. It was found that,
at a given temperature, the solubility of MPC decreased exponentially with
time and a master curve was obtained using a temperature–time
superposition. Gel electrophoresis indicated that the insoluble proteins were
the caseins, whereas the whey proteins remained soluble. Mass spectrometry
showed that, with storage time, the casein was lactosylated. In the light of
these measurements, it is speculated that the insolubility of the MPC could
have been due to cross-linking of the proteins at the surface of the MPC
powder.
Roman and Sgarbieri (2006) reported that the hydrophilic and surfactant
properties of casein concentrates made by different processes such as
isoelectric precipitation and neutralization (commercial casein, CC)
coagulation by rennet (casein clots, COC) and microfiltration/diafiltration
(casein micelles, CM). Water absorption capacity (WAC), water solubility
(WS) and water-holding capacity (WHC) were highest for CM and lowest
for COC. Solubility was higher in water for both CM and COC. Foaming
capacity was better for CM than for CC. Foam stability was low for both
CM and CC but it was high for CM and for CC in the absence of salt.
Emulsifying capacity was higher for CC. Stability of emulsion was high for
CC at pH 4.0 and for CM at pH 7.0.
Onwulata et al., (2006) reported that WPI pastes (60% solids) were
extruded in a twin-screw extruder at 100°C with 4 pH-adjusted water
streams: acidic (pH 2.0 ± 0.2) and alkaline (pH 12.4 ± 0.4) streams from 2 N
HCl and 2 N NaOH. Acidic (pH 2.5 ± 0.2) and alkaline (pH 11.5 ± 0.4)
electrolyzed water streams; these were compared with WPI extruded with
deionized water. Alkaline conditions increased insolubility caused yellowing
and increased pasting properties significantly. Acidic conditions increased
solubility and decreased WPI pasting properties. Subtle structural changes
occurred under acidic conditions, but were more pronounced under alkaline
conditions.
54
Sinha et al., (2007) results revealed that the functional and nutritional
properties of enzymatically hydrolyzed WPC and to formulate a beverage
mix. The water absorption capacity of WPC was 10 ml/100 g and increased
in enzyme treated samples from 16 to 34 ml/100 g with increase in the time
of hydrolysis. Emulsion capacity (45 ml of oil/g of control WPC) showed a
decreasing trend with increasing time of hydrolysis. The gel filtration pattern
of enzyme treated samples increase in low molecular weight fractions. The
content of methionine in samples treated with enzymes is higher, compared
to the control. The in vitro protein digestibility of untreated WPC was 25%
and increased in all treated samples to varying degrees (69–70%).
Formulated beverage had 52% protein, 10% fat and 6.6% ash. There were
no significant differences in the sensory attributes of formulated and
commercial beverage.
Dangaran and Krochta (2007) stated that WPI films plasticised with
sucrose were stored in 53% relative humidity for up to 60 days. The oxygen
permeability, tensile properties and gloss of the films were measured.
Changes in properties were compared with changes in WPI films plasticised
with glycerol (no crystallisation) or plasticised with sucrose (crystallisation)
plus a crystallisation inhibitor. The inhibitors hindered sucrose
crystallisation, and the desired film properties were maintained for a longer
period of time. Raffinose was the more effective inhibitor, maintaining the
film flexibility and barrier properties for over 28 days and maintaining gloss
at almost 90% of the initial value for 60 days of storage.
Cheison et al., (2007) observed that whey protein isolate (WPI) was
hydrolyzed to whey protein hydrolysates (WPH) of degree of hydrolysis
equal to 15% using Protease N ‗Amano‘ G (IUB 3.4.24.28) in a batch
reactor at 55 °C and pH 7.0 according to the pH-stat procedure. Ash was
removed by adsorbing WPH onto macroporous adsorption resins (MAR).
Kim et al., (2007) examined the effects of enzymes on the production and
antigenicity of native and heated WPC hydrolysates. Native and heated (10
55
min at 100˚C) WPC (2% protein solution) were incubated at 50˚C for 30, 60,
90 and 120 min with 0.1, 0.5 and 1% pepsin and then with 0.1, 0.5 and 1%
trypsin on a protein equivalent basis. Results suggested that incubation of
heated WPC with 1% pepsin and then with 1% trypsin was the most
effective for producing low antigenic hydrolysates by WPC hydrolysis and
obtaining low molecular weight small peptides.
Herceg et al., (2007) observed that the interactions between whey proteins
(whey protein isolate (WPI), whey protein concentrate (WPC) and β-
lactoglobulin) and carbohydrates (glucose, sucrose, starch and inulin) on
some physical and functional properties of whey proteins and carbohydrates
suspensions (10% dry matter (w/v)). Carbohydrate addition in model
suspensions of whey proteins resulted in significantly enhanced foam
stability of protein suspensions (FSI; MFS). Model systems were also
analyzed for emulsion activity index (EAI) and emulsion stability index
(ESI) by the turbidometric technique. EAI and ESI values increased
significantly in model suspensions prepared with WPI and β-lactoglobulin in
combination with mono and disaccharides.
Tosi et al., (2007) studied that the influence of thermal treatment on foaming
properties of sweet whey solutions. The tests were carried out on solutions
of cheese sweet whey powder by a factorial experiment design of two
variables, namely treatment temperature and time, at three levels, 75, 80 and
85 °C, and 300, 750 and 1200 s. Selected responses were foam volume,
liquid volume in foam, foam forming power and foam stability. The applied
thermal treatments modified foam properties in such a way that the foam
volume of thermally treated samples was always higher than that of the non-
treated samples, with the exception of that treated at 85 °C for 750 s.
Stability also behaved in the same way, except the sample treated at 75 °C
for 300 s.
Wang et al., (2007) assessed the film-forming abilities of six types of
proteins, as well as six types of polysaccharides at various concentrations
56
(proteins: 0–16%; polysaccharides: 0–4%) and heating temperatures (60–
80 °C). Biopolymer films evaluated included: sodium caseinate (SC), whey
protein isolate (WPI), gelatine (G); caboxymethyl cellulose (CMC), sodium
alginate (SA) and potato starch. Film-forming conditions were achieved
using SC and G (4% and 8%), WPI (8% and 12%), PS, CMC (2% and 3%)
or SA (1% and 1.5%) solutions heated to 80 °C in combination with 50%
(w/w) glycerol. Films manufactured from 1.5% SA, 8% G and 3% CMC had
the highest tensile strength (24.88 MPa); flexibility (89.69%) and puncture
resistance (22.66 N). SC, WPI and G-based films were more resistant to
solvent than SA, CMC and PS.
Zhong and Jin (2008) revealed that the WPI and WPC powders and a 10%
(wt/vol) WPI solution were treated with supercritical carbon dioxide
(scCO2). The WPI solution was treated at 40°C and 10 MPa for 1 h whereas
WPI and WPC powders were treated with scCO2 at 65°C and 10 or 30 MPa
for 1 h. The improvement in gelling properties was more significant for the
scCO2-treated WPC. In addition, the scCO2-processed WPI and WPC
powders appeared to be fine and free-flowing in contrast to the clumps in the
unprocessed samples. The results suggest that functionalities of whey
proteins can be improved by scCO2 treatment to produce novel ingredients.
Wang et al., (2008) stated that response surface methodology (RSM) was
used to investigate pH and corn oil (CO) effects on the properties of films
formed from WPI. Test films were evaluated for tensile strength (TS),
puncture strength (PT), percentage elongation at break point (E), water
vapour permeability (WVP) and oxygen permeability (OP). When WPI
solution pH increased, film TS generally decreased with CO addition. E
values increased dramatically with increasing levels of CO when pH for
WPI solutions were >8.5. WPI solutions possessing high pH values
produced WPI films with the highest PT values. WVP had a quadratic
relationship with pH and CO addition. OP had an inversely linear
57
relationship with increasing pH and a quadratic relationship with CO
addition.
Michael et al., (2008) suggested that the WPC higher than WPI for milky,
sweet, and caramel flavors. Instrumental analysis showed that WPC
products had a greater number of volatiles than WPI products. Sensory
results indicated that the flavor of WPC and WPI was not affected by
instantizing, ion exchange, or bleaching; alternatively, instrumental results
indicated slight differences in numbers of volatiles identified for each
aforementioned process.
Kucukcetin (2008) studied that different heat treatments (95 ˚C/ 256 s, 110
˚C/ 180 s and 130 ˚C/ 80 s) were applied to the yoghurt milk with the CN to
WP ratio of 1.5:1, 2:1, 3:1 and 4:1. Physical properties, including graininess
and roughness of stirred yoghurt were determined during storage at 4 ˚C for
15 days. Visual roughness number of grains, perimeter of grains, storage
modulus and yield stress decreased, when heating temperature or CN to WP
ratio increased.
Lim et al., (2008) studied that use of high hydrostatic pressure (HHP) to
improve functional properties of fresh WPC, compared with functional
properties of reconstituted commercial whey protein concentrate 35 (WPC
35) powder. Additionally, HHP-WPC treated at 300 MPa for 15 min
acquired larger overrun than commercial WPC 35. The HHP treatment of
300 MPa for 0 min did not improve foam stability of WPC. However, WPC
treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited
significantly greater foam stability than commercial WPC 35. The HHP
treatment was beneficial to enhance overrun and foam stability of WPC.
Kresic et al., (2008) revealed that the effects of three emerging
technologies: high pressure (HP: 500 MPa, 10 min), ultrasound (US:
20 kHz, 15 min) and tribomechanical activation (TA: 40000 rpm) on
flowing behaviour and thermophysical properties of WPI and WPC. HP and
58
US were carried out on 10% (w/w) model dispersions while for TA samples
were in powdered form. Pressurization caused significant decrease in
solubility of WPC and WPI, while both samples treated with US and TA
exhibited significantly better solubility compared to control. Apparent
viscosity data described with power law equation (r2 = 0.97–0.99)
significantly increased after all treatments while HP caused the most
intensive changes in rheological behaviour.
Padiernos et al., (2009) evaluate the foaming properties of selected low-fat
whipping cream formulations containing whey protein concentrate (WPC)
that did or did not undergo high hydrostatic pressure (HHP) treatment.
Whipping cream containing untreated WPC and HHP-treated WPC resulted
in greater overrun and foam stability than the control whipping cream
without WPC. High hydrostatic pressure-treated WPC can improve the
foaming properties of low-fat whipping cream.
Guyomarch et al., (2009) revealed that the aggregates were formed by
heating mixtures of whey protein isolate (WPI) and pure κ-casein or sodium
caseinate at pH 7 and 0.1 M NaCl. The aggregates were characterized by
static and dynamic light scattering and size exclusion chromatography. After
extensive heat-treatment at 80 °C for 24 h, almost all whey proteins and κ-
casein formed mixed aggregates. At a given WPI concentration the size of
the aggregates decreased with increasing κ-casein or sodium caseinate
concentration, but the overall self-similar structure of the aggregates was the
same. The presence of κ-casein or caseinate therefore inhibited growth of the
heat-induced whey protein aggregates.
Sugiarto et al., (2009) studied that the binding of iron (ferrous sulphate) to
two commercial milk protein products, sodium caseinate and WPI dissolved
in 50 mM HEPES buffer was examined as a function of pH and iron
concentration. Sodium caseinate had more sites (n=4) than WPI (n=8) for
binding iron and the affinity of caseinate to bind iron was also higher than
that of WPI. These differences were attributed to the presence of clusters of
59
phosphoserine residues in casein molecules. The amount of iron bound to
sodium caseinate was found to be independent of pH in the range 5.5 – 7.0
whereas acidification (pH range 7.0 – 3.0) caused a marked decrease in the
amount of iron bound to WPI.
Kuhn et al., (2010) stated that cold-set whey protein isolate (WPI) gels
formed by sodium or calcium chloride diffusion through dialysis membranes
were evaluated by mechanical properties, water-holding capacity and
microscopy. The increase of WPI concentration led to a decrease of porosity
of the gels and to an increase of hardness, elasticity and water-holding
capacity for both systems (CaCl2 and NaCl). WPI gels formed by calcium
chloride addition were harder, more elastic and opaque, but less deformable
and with decreased ability to hold water in relation to sodium gels.
Gauche et al., (2010) reported that at temperatures higher than 85 ˚C the
apparent viscosity measurements of whey protein solutions with
transglutaminase were significantly higher than those of the control samples.
DSC analysis showed that thermal denaturation occurred at temperatures
close to 82 ˚C and the enzymatic reaction was enhanced at higher
temperature. The gel point of whey proteins decreased with transglutaminase
addition. This decrease became greater as a function of reaction time due to
the formation of high weight protein polymers catalyzed by
transglutaminase, which was also observed in the turbidity analysis.
Chai et al., (2010) reported that effect of the free and the pre-encapsulated
calcium ions on the physical properties of the WPI film were studied for
improving calcium content in the edible films. At pH 8, the film-forming
process was hindered by serious protein aggregation and gelation caused by
0.5% (w/w) free calcium ions added in an 8% WPI solution. If the calcium
ions were pre-encapsulated in the protein microparticles (contained 17%
Ca2+) using spray drying method, and then added in the film-forming
solution prepared using the same protein, the calcium content could be
60
doubled (1%, w/w) without significant effects on the physical properties of
the film.
Evans et al., (2010) studied that identify and compare the composition,
flavor, and volatile components of 80% serum protein concentrates (SPC)
and whey protein concentrates (WPC). Each pair of 80% SPC and WPC was
manufactured from the same lot of milk. Consumer acceptance testing of
acidified 6% protein beverages made with 80% SPC and WPC produced in
the pilot plant and with WPC from commercial sources was conducted. The
SPC was lower in fat and had a higher pH than the WPC produced in the
pilot plant or commercial WPC. The pilot-plant WPC had higher
concentrations of lipid oxidation products compared with SPC, which may
be related to the higher fat content of WPC. There was a large difference in
appearance between 80% SPC and WPC: solutions of SPC were clear and
those of WPC were opaque.
Kelly et al., (2010) observed that the effects of protein concentration on
astringency and interactions between whey and salivary proteins. Changes in
astringency with protein concentration depended on pH. At pH 3.5,
astringency significantly increased with protein concentration from 0.25 to
4% (wt/wt) and then remained constant from 4 to 13% (wt/wt). Furthermore,
saliva flow rates increased with increasing protein concentrations. Maximum
turbidity of whey protein–saliva mixtures was observed between pH 4.6 and
5.2. Both sensory evaluation and in vitro study of interactions between β-LG
and saliva indicate that astringency of whey proteins is a complex process
determined by the extent of aggregation occurring in the mouth, which
depends on the whey protein beverage pH and buffering capacity in addition
to saliva flow rate.
Hiller and Lorenzen (2010) revealed that milk proteins were modified by
Maillard reaction with glucose, lactose, pectin and dextran and analysed for
changes in molar mass distribution and functional properties. Further
concluded that oligomeric (20,000–200,000 g/mol) and polymeric
61
(>200,000 g/mol) Maillard reaction products with heterogeneous functional
property. Compared to untreated milk proteins, milk protein/saccharide
Maillard products formed highly viscous solutions and performed increased
antioxidant capacity. Improved heat stability and increased overrun for milk
protein/pectin and milk protein/dextran products.
Mimouni et al., (2010) studied that a sample preparation method for
scanning electron microscopy analysis of rehydrated milk protein
concentrate (MPC) powder particles and used to characterize the time course
of dissolution and the effects of prior storage on the dissolution process. The
results show that a combination of different types of interactions (e.g.,
bridges, direct contact) between casein micelles results in a porous, gel-like
structure that restrains the dispersion of individual micelles into the
surrounding liquid phase without preventing water penetration and
solubilization of nonmicellar components. During storage of the powder,
increased interactions occur between and within micelles, leading to
compaction of micelles and the formation of a monolayer skin of casein
micelles packed close together, the combination of which are proposed to be
responsible for the slow dissolution of stored MPC powders.
Singh (2011) stated that milk proteins usually exert several interdependent
functional properties simultaneously in each food application. The
functional properties of proteins vary with pH, temperature, ionic strength,
and concentration of calcium and other polyvalent ions, sugars, and
hydrocolloids, as well as with processing treatments. In addition, the
processes used in the manufacture of milk protein products can modify the
native structures of proteins, which can lead to further protein–protein
interactions, consequently affecting the protein functionality.
Foegeding et al., (2011) suggested that the significant progress in the
utilization of whey protein has been made in the past 30 years and the future
growth of whey utilization is expected to be led by the industry‘s increasing
62
focus on nutritional products, particularly in the dietary, sports and clinical
segments of the market.
Huang et al., (2011) reported that the use of whey protein isolate (WPI)
edible coatings to improve the rehydration behaviour of freeze-dried (FD)
strawberry pieces. First, the optimal ratio sample volume of coating solution
was optimised by determining the rehydration ratio, bulk density and
nutritional quality of the samples. Second, the effect of changing the pH and
the variation in temperature–time to denaturate WPI on rehydration
characteristics was also evaluated. The rehydration ratio of strawberry pieces
decreased with increasing the denaturation temperature and time, while it
increased with increasing pH of the coating solution.
Nicorescu et al., (2011) studied to compare the effect of thermal treatments
on the foaming properties of whey protein isolate (WPI) and egg white
proteins (EWP): EWP was pasteurized in dry state from 1 to 5 days and
from 60 °C to 80 °C, while WPI was heat-treated between 80 °C and 100 °C
under dynamic conditions using a tubular heat exchanger. WPI exhibited a
higher foamability than EWP. For WPI, heat treatment induced a slight
decrease of overrun when temperature was above 90 °C. Further concluded
that the dry heat treatment of EWP provided softer foams, despite more rigid
than the WPI-based foams, whereas dynamically heat-treated WPI gave
firmer foams than native proteins.
Hemar et al., (2011) observed that fluorescence spectroscopy was used to
investigate the interaction between resveratrol and whey proteins. The whey
proteins examined were lactoferrin, holo-lactoferrin, apo-lactoferrin, whey
protein isolate (WPI) and the β-lactoglobulin- and α-lactalbumin-rich
fractions of WPI. In all the systems studied, it was found that resveratrol
interacted with the whey proteins to form a 1:1 complex. The binding
constant, Ks, for the protein–resveratrol complex for all the proteins
examined varied from 1.7 × 104 to 1.2 × 105 m−1.
63
Kizeminski et al., (2011) studied that the effect of whey protein addition on
structural properties of stirred yoghurt systems at different protein and fat
content was studied using laser diffraction spectroscopy, rheology and
confocal laser scanning microscopy (CLSM). The composition of heated
milk systems affected micro- and macroscopic properties of yoghurt gels.
Particle size increased as a function of increasing whey protein content and
decreased as a function of increased fat level.
Listiyani et al., (2011) stated that the hydrogen peroxide (HP) bleached
WPC 34% displayed higher cardboard flavor and had higher volatile lipid
oxidation products than benzoyl peroxide (BP) bleached or control WPC34.
Benzoyl peroxide-bleached WPC34 had higher benzoic acid (BA)
concentrations than unbleached and HP bleached WPC34 and BA
concentrations were also higher in BP-bleached WPC80 compared with
unbleached and HP-bleached WPC80, with smaller differences than those
observed in WPC34. Benzoic acid extraction from permeate showed that
WPC80 permeate contained more BA than did WPC34 permeate. Benzoyl
peroxide is more effective in color removal of whey and results in fewer
flavor side effects compared with HP and residual BA is decreased by
ultrafiltration and diafiltration.
Yang and foegeding (2011) explain the macroscopic foaming properties of
egg white protein (EWP) and whey protein isolate (WPI). Foam properties
were altered by adding different amounts of sucrose (4.27–63.6 g/100 mL).
Addition of sucrose decreased the initial bubble size, corresponding to
higher foam stability and lower air phase fraction. EWP foams were
composed of smaller bubbles and lower air phase fractions than WPI foams.
Increased sucrose concentration caused a decreased liquid drainage rate due
to a higher continuous phase viscosity and smaller bubble sizes. WPI foams
had faster rates for liquid drainage and bubble coarsening than EWP foams.
Campbell et al., (2011) stated that the effect of annatto color and starter
culture on the flavor and functionality of whey protein concentrate (WPC).
64
Cheddar cheese whey with and without annatto (15 mL of annatto/454 kg of
milk, annatto with 3% wt/vol norbixin content) was manufactured using a
mesophilic lactic starter culture or by addition of lactic acid and rennet.
Pasteurized fat-separated whey was then ultrafiltered and spray dried into
WPC. WPC manufactured from whey with starter culture compared with
WPC from rennet-set whey. The WPC with annatto had higher
concentrations of p-xylene, diacetyl, pentanal, and decanal compared with
WPC without annatto. Results suggest that annatto has a no effect on whey
protein flavor, but that the starter culture has a large influence on the
oxidative stability of whey.
Whitson et al., (2011) studied that the effects of holding time of liquid
retentate on flavor of spray-dried whey proteins: Cheddar whey protein
isolate (WPI) and Mozzarella 80% whey protein concentrate (WPC80).
Liquid WPC80 and WPI retentate were manufactured and stored at 3°C.
After 0, 6, 12, 24, and 48 h, the product was spray-dried (2 kg) and the
remaining retentate held until the next time point. Powders were stored at
21°C and evaluated every 4 mo throughout 12 mo of storage. Sensory
results, lipid oxidation products (hexanal, heptanal, octanal) and sulfur
degradation products (dimethyl disulfide, dimethyl trisulfide) increased in
spray-dried products with increased liquid retentate storage time, whereas
diacetyl decreased. Shelf stability was decreased in spray-dried products
from longer retentate storage times.
Ye (2011) revealed that the emulsifying properties of milk protein
concentrates (MPC) and stabilities of emulsions formed with MPCs by
examining emulsions formation, adsorption behaviours of proteins and
emulsion microstructures. Compared with emulsions formed with higher
calcium MPCs at a given protein concentration, emulsions formed with low
calcium MPCs were finer, the total surface protein concentration was lower
and the protein composition on the surface of the emulsion droplets was
altered. In low-calcium-MPC-stabilized emulsions, the stability of the
65
emulsions decreased with an increase in the emulsion size at low protein
concentrations.
Zhu and Damodaran (2012) observed that the extent of partitioning of
annatto between protein, milk fat globule membrane (MFGM), and aqueous
(serum) phases of cheese whey. The MFGM was separated from Cheddar
cheese whey and quantitative analysis of the distribution of annatto in the
fat-free whey protein isolate (WPI), the MFGM fractions, and the serum
phase revealed that annatto was not bound to the protein fraction. The results
showed that a colorless WPI or whey protein concentrate could be produced
from Cheddar cheese whey by separation of MFGM from the whey,
followed by diafiltration.
Ramos et al., (2012) reported that the effectiveness of antimicrobial edible
coatings to wrap cheeses, throughout 60 d of storage, as an alternative to
commercial nonedible coatings. Coatings were prepared using whey protein
isolate, glycerol, guar gum, sunflower oil, and together with several
combinations of antimicrobial compounds—natamycin and lactic acid,
natamycin and chitooligosaccharides (COS), and natamycin, lactic acid, and
COS. Application of coating on cheese decreased water loss (~10%, wt/wt),
hardness, and color change; however, salt and fat contents were not
significantly affected. The antimicrobial edible coating containing
natamycin and lactic acid was the best in sensory terms.
Hussain et al., (2012) reported that the 5% (wt/vol) whey protein isolate
(WPI) dispersion (pH 6.5) with different concentrations of NaCl was
submitted to dynamic heat treatment. The gelation temperature was also
influenced by ionic strength and an increase in denaturation temperature and
thermal stability was also observed by using differential scanning
calorimetry. Results demonstrated the strong interaction between ionic
strength and dynamic thermal treatment on protein functional properties and
their careful adjustment could enable the food industry to effectively use
WPI as a gelling agent.
66
Jervis et al., (2012) stated that compare two commercially approved
bleaching agents, benzoyl peroxide (BP) and hydrogen peroxide (HP), and
their effects on the flavor and functionality of WPC 80%. Colored and
uncolored liquid wheys were bleached with BP or HP, and then ultrafiltered,
diafiltered, and spray-dried; WPC80 from unbleached coloured and
uncoloured Cheddar whey were manufactured as controls. The HP-bleached
WPC80 were higher in lipid oxidation compounds and had higher fatty and
cardboard flavors compared with the other unbleached and BP-bleached
WPC80. The WPC80 bleached with BP had lower norbixin concentrations
compared with WPC80 bleached with HP. Whey bleached with HP
treatments had more soluble protein after 10 min of heating at 90°C at pH
4.6 and pH 7 than the no-bleach and BP treatments, regardless of additional
colour. Overall, HP bleaching caused more lipid oxidation products and
subsequent off-flavors compared with BP bleaching. However, heat stability
of WPC80 was enhanced by HP bleaching compared with control or BP-
bleached WPC80.
Dissanayake et al., (2012) reported that the effect of microparticulation at
low pH on the functionality of heat-denatured whey proteins (WP). Spray-
dried microparticulated WP (MWP) powders were produced from 7%
(wt/wt) WP dispersions at pH 3, acidified with citric or lactic acid and
microfluidized with or without heat denaturation. Microparticulated WP
exhibited enhanced heat stability as indicated by thermograms, along with
better emulsifying properties compared with those produced at neutral pH.
However, MWP powders created weaker heat-induced gels at neutral pH
compared with controls. However, they created comparatively strong cold
acid-set gels. At low pH a combination of heat and high hydrodynamic
pressure produced WP micro-aggregates with improved colloidal stability
that affects other functionalities.
67
2.3 Microbiological quality of idli
The microbiological studies were carried out to assess the standard of
cleanliness during production, packaging, transportation and storage and for
evaluating the shelf life of idli. The market samples of idli analysed at
Department of Food Technology, Tirupathi, Andhra Pradesh (Suneetha et
al., 2011) were heavily contaminated with variety of organisms.
Mukherjee et al., (1995) stated that the micro-organisms responsible for the
characteristic changes in the batter were isolated and identified. Although
there is a sequential change in the bacterial flora, the predominant micro-
organisms responsible for souring as well as for gas production, was found
to be Leuconostoc mesenteroides. In the later stages of fermentation, growth
of Streptococcus faecalis and still later of Pediococcs cerevisiae becomes
significant. The fermentation of idli demonstrates a leavening action caused
by the activity of the hetrofermentative lactic acid bacterium, L.
mesenteroides. As far as is known, this is the first record of a leavening
action produced exclusively by the activity of a lactic acid bacterium.
Kaw (1995) observed that batter volume showed an increase up to 24 hr of
fermentation period and non- amylose variety IR29 showed the maximum
expansion. Microbial counts in idli batter which were low initially increased
steeply with the advancement in fermentation time. Maximum counts of
Lctobacilli and coliforms were obtained after 12 h and those of yeasts and
molds after 24 h fermentation. Sensory evaluation revealed that idlis made
from IR29, the waxy variety of rice were unacceptable and significantly
different from the amylase type of rice varieties. While no significant
differences between the rice varieties were observed for aroma, density, off-
flavour and fermented flavour, the differences in cohesiveness, coarseness
and general acceptability were significant. Highly positive correlations were
revealed between pH and reducing sugars, batter volume and total acidity,
total acidity and non- protein nitrogen and highly negative correlations of
pH with total acidity and non protein nitrogen. Yeasts and molds had highly
68
significant and positive association with batter volume, non- protein nitrogen
and total acidity. Lactobacilli revealed significantly negative correlations
with reducing sugars and pH.
Soni et al., (1996) reported that bacteria alone or in combination with yeasts
were found to be responsible for the fermentation of dosa. Leuconostoc
mesenteroides, Streptococcus faecalis, Lactobacillus fermentum and
Bacillus amyloliquefaciens were the predominant bacteria responsible for
souring and leavening of dosa batter. Yeasts whenever present, belonged
mainly to Saccharomyces cerevisiae, Debaryomyces hansenii and
Trichosporon beigelli. They produced flavour, enzymes and helped in the
saccharification of starch. Both bacteria and yeasts were contributed by the
ingredients Oryza sativa and Phaseolus mungo. The prevalence of bacteria
and yeasts was affected by seasonal variations but bacteria always
dominated the overall microbial load.
Soni and Sandhu (1998) stated that idli prepared from a fermented batter
containing both rice (Oryza sativa) and black gram (Phaseolus mungo).
Analysis of 35 different samples of idli batter, both commercial and
laboratory prepared, revealed the occurrence of bacteria belonging to six
species in the range of 106 – 109 / g, 68% of the samples were also positive
for yeasts, ranging up to 106 / g and yielding six types. Laboratory studies on
ways to improve the nutritional and organoleptic properties of idli identified
changes in fermentation conditions that led to appreciable increases in the
microbial cell counts, total acids volume, soluble solids, reducing sugars,
non- protein nitrogen, free amino acids, amylases, proteinases and water
soluble vitamins, including B2, B2, B12, and C. Novel idli batters, prepared
by replacing the conventional black gram with other legumes, revealed
comparable changes but with differences in the levels of some biochemical
constituents. Incubation of idli batters at 28 ˚C with initial pH around 4.5
and supplemented with sucrose (1- 2%) proved to be favourable for
improving the nutritional constituents and organoleptic characteristics.
69
Jama and Varadaraj (1999) stated that the inherent viable bacterial
populations of mesophilic aerobes and lactics in idli batter increased in their
numbers with time at 35 ˚C reaching numbers in the range of 13 to 15 log10
CFU g -1. Simultaneously, the pH level decreased from 6.2 to 4.4. Strains of
Bacillus cereus F 4810, Escherichia coli D 21 and Staphylococcus aureus
FRI 722 (foodborne pathogens) introduced into the idli batter at an initial
level of 4.3 log10 CFU g -1 was able to survive and grow well in an initial
period of 6 h. However, the strain of S. aureus showed a constant increase in
its numbers reaching 9.3 log10 CFU g -1 in 12 h. The addition of plantaricin
LP84, a bacteriocin produced by Lactobacillus plantarum NCIM 2084 to idli
batter at 1% (v/w) level was able to retard the growth of the inoculated
cultures during fermentation.
Roy et al., (2007) examined six different type samples of legume-based
popular fermented foods viz. amriti, dhokla, dosa, idli, papad and wadi
purchased from retail outlets in West Bengal. These market samples carried
higher micro-organisms counts than laboratory sample. In this study the
result indicated that these foods were manufactured using poor quality
starting materials, processed under unhygienic conditions or/ and
temperature abused during transportation and storage.
Lyer et al., (2011) observed that idli batter was used as a source for isolation
of lactic acid bacteria (LAB). A total of 15 LAB strains were isolated on the
basis of their gram nature and catalase activity. Of these, one lactobacilli
strain and one lactococci strain which showed antimicrobial activity were
identified using biochemical characterization, sugar utilization and
molecular sequencing. The microbes, labelled as IB-1 (Lactobacillus
plantarum) and IB-2 (Lactococcus lactis) were tested for their in vitro
tolerance to bile salts, resistance to low pH values and acidifying activity.
Both the strains showed good viability (IB-58.11%, IB-60.84%) when
exposed to high bile salt concentration (2%) and acidic pH of ≤ pH 3.0 (IB1-
88.13%, IB2-89.85%).
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Hussain and Uddin (2011) studied that the total microbial load in
germinated wheat and mungbean seed flour for preparing of weaning foods.
The plates were incubated at (35 ± 1) °C for 48h, and the numbers of
bacterial colonies and of yeast and mould colonies are counted. The results
show that the total viable counts were ranged from 1.7 x 102 cfu/g -9.3 x
102 for wheat seed flour cfu/g, , and1.7 x 102 - 6.0 x 102 cfu/g for the
mungbean seed flour. It was concluded that flour was prepared at 33°C for
60 hour was safe in sense of microbiological purity and can be used for
weaning food preparation.
2.4 Health benefits of whey protein concentrate (WPC)
Renner (1992) suggested that a high quality protein with significant
quantities of essential amino acids such as lysine, methionine and
tryptophan, WPC can be used for supplementing plant proteins in
developing high protein foods and other special dietetic foods.
Pihlanto and Korhonen (2003) suggested that significant amounts of
essential amino acids, whey proteins possess excellent biological active
peptide sequences that promote good health.
Vermeirssen et al., (2003) stated that in vitro gastrointestinal digestion was
the predominant factor controlling the formation of angiotensin-I-converting
enzyme (ACE) inhibitory activity, hence indicating its importance in the
bioavailability of ACE inhibitory peptides.
Xu (2009) evaluated the effects of whey protein on osteoblasts. The whey
protein was added to the culture medium at concentrations of 0.02 and
0.1 mg/mL. In vitro, whey protein stimulated the proliferation and
differentiation of osteoblasts cultured in different concentrations of whey
protein. The levels of osteocalcin and insulin-like growth factor-I in the
culture medium also increased. Real-time reverse transcription-PCR results
showed that the mRNA expression of osteoprotegerin (OPG) and receptor
activator of nuclear factor-κ B ligand (RANKL) increased in the cells in a
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dose-dependent manner, and when the results were expressed as
OPG/RANKL ratio, a significant increase could be seen in the 0.1 mg/mL
whey protein group. Results showed that the active component in the whey
protein plays an important role in bone formation and a potential therapeutic
role in osteoporosis by activating osteoblasts.
2.5 Uses of whey protein concentrate (WPC)
Whey protein concentrate (WPC) by virtue of their high protein content and
functionality are increasingly used in a great number of food products, for
replacing traditional additives like milk powder, egg albumin based foods
and is now finding applications in infant and dietetic foods, ice cream and
frozen beverages, meat products, pasta and Indian traditional products like
khoa.
Vitti (1991) reported that the composition and functional properties of whey
protein concentrate (WPC) are such that it can be used to replace egg partly
in bread and cakes.
Thompson and Reniers (1992) were determined the effects on quality and
acceptance on succinylated whey concentrate was substituted for sodium
caseinate in the formulation of coffee whitener and for 20% of the egg yolk
in salad dressing. Succinylated whey concentrate has emulsification
properties suitable to these products. A coffee whitener was obtained with
higher viscosity, greater stability, lower whitening power, and greater
acceptability than the control sample made with sodium caseinate. Similarly,
a more stable salad dressing with a higher viscosity and no significant
difference in acceptability was produced.
Thompson et al., (1993) revealed that the effect on quality of substituting
succinylated cheese whey protein concentrate for nonfat dry milk in ice
cream and instant pudding. The use of succinylated whey protein
concentrate in ice cream increased viscosity and resistance to melting and
reduced freezing time and overrun. In the absence of stabilizers and
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emulsifiers, trends were the same and ice cream remained stable.
Incorporating succinylated whey protein concentrate into instant pudding
increased hydration and retarded rate of firming during storage.
Modler et al., (1993) studied that the eighteen skim milk yogurts, prepared
from all combinations of six protein types (three casein- and three whey-
based products) and three protein concentrations (.05, 1.0, and 1.5% added
protein). Addition of increasing amounts of protein increased gel firmness
and decreased syneresis. The casein-based proteins, particularly sodium
caseinate, produced yogurts that were generally inferior to gelatin for
smoothness and appearance. WPC at 1.0 and 1.5% of protein addition,
produced yogurts generally superior to casein-based products for both
appearance and smoothness.
Rajorhia et al., (1990) incorporated 10 and 18% WPC (27.14% TS) solids
in buffalo milk for the manufacture of khoa. Greater amount of WPC
produced bigger grains in khoa, which is a desirable property for preparing
kalakand.
Mccane and Widdowson (1991) suggested that whey protein concentrate
(WPC) contains 70- 75% protein and is being used to enrich soft drinks and
other beverages, infant foods, ice cream and yoghurt.
Gruetzmacher and Bradley (1991) examined to use as a replacement for
sodium caseinate in spray-dried coffee whiteners. Fifty-two spray-dried
coffee whitener formulations were prepared using demineralized acid whey
protein concentrate and compared with standard commercial whitener
formulations. Optimal stability and functionality were obtained at 1.5% acid
whey protein. A dipotassium phosphate to protein ratio of 1.0 yielded good
stability. Demineralized acid whey protein was an acceptable replacement
for sodium caseinate in spray-dried coffee whiteners and can replace sodium
caseinate at a 1:2 ratio.
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Hofi et al., (1993) suggested that whey protein concentrate (WPC) have
been successfully used in frozen desserts for years because they bind water
and form weak networks that mimic the structure of full fat ice cream.
Patel et al., (1993) studied that the addition of 5% WPC solids to cow milk
improved the flavour, body and texture and colour of khoa prepared. WPC
incorporated cow milk khoa compared well with the traditional buffalo milk
khoa.
Brandsma and Rizvi (2001) studied that Low-moisture, part-skim (LMPS)
Mozzarella cheeses were made from highly concentrated skim milk
microfiltration (MF) retentate and butteroil. Differing combinations of
rennet concentration, coagulation temperature and post-coagulation curd
cutting time were used, with comparisons made of the rheological and
functional characteristics of cheeses during ageing. Rennet concentration
was the only experimental factor to significantly affect MFM rheological
and functional development.
Dewani and Jayaprakasha (2002) studied that whey solids (in the form of
WPC) can be effectively used in the preparation of khoa and khoa based
sweets such as peda and gulabjamun by properly inducing selective heat
treatment, optimizing levels of pre-concentration and blending whey protein
concentrate (WPC) and milk in appropriate proportions. Further peda and
gulabjamun were prepared by the standard methods. With the increase in
levels of WPC in the admixture, yield, acidity, hydroxyl methyl furfural
(HMF) and penetration values increased correspondingly whereas fat,
protein, lactose, moisture and ash content decreased. Sensory attributes of
peda increased upto 40% and 50% WPC levels. Similarly gulabjamun with
30% WPC level was found to be on compare with the control.
Kumar and Sangwan (2002) observed that whey protein concentrate (WPC
15% w/v) were hydrolysed with trypsin, α- chymotrypsin and papain
enzymes separately and influence of enzymatic hydrolysis on emulsifying
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properties. The emulsifying activity index (EAI) and emulsifying capacity
(EC) increased up to certain level of hydrolysis and decreased on future
hydrolysis at pH 7.0. In case of trypsin and papin, the maximum ESI and EC
was found after 2 h of hydrolysis while it was after 1 h in α- chymotrypsin
hydrolysed sample.
Mleko and Gustaw (2002) studied that dairy desserts with starch, k-
carrageenan and total milk proteins were prepared and their rheological
behaviour was compared with desserts obtained by substitution of milk
protein by whey proteins. As whey protein desserts were held at 90 ˚C for 5
min, an increase in apparent viscosity was observed. In comparison to whey
proteins, total milk proteins produced desserts with lower apparent viscosity.
Holding at 90 ˚C did not increase of apparent viscosity and there was
smaller increase in apparent viscosity as the samples were cooled.
Dewani and Jayaprakasha (2002) reported that replacement of MSNF up
to 30% with WPC resulted in increased overall acceptability scores of
gulabjamun. A mechanized semi-continuous system has been developed for
the manufacture of gulabjamun from khoa at commercial scale.
Aryana et al., (2002) observed that the functionality of various
combinations of egg white (EW), whey protein concentrate (WPC) and
bovine serum albumin (BSA) and compare the microstructures of their gels.
The combination of WPC with EW or BSA resulted in a synergistic effect
for thermostability (TS) and foam stability (FS) and an additive effect for oil
holding capacity (OHC), water holding capacity (WHC), foam density (FD),
emulsifying activity index (EAI), gel stress and strain. On the contrary, an
antagonistic effect was observed for FA. If a multifunctional combination
was to be picked, it would be a 1 : 1 ratio of WPC and BSA as it had the
highest number of attributes with synergistic effects.
Singh et al., (2003) studied that egg was replaced with WPC at levels of 0 to
100%. Replacement of egg with WPC up to 50% did not result in significant
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differences in physical properties of cake, thereafter differences were
significant except for the cells of the cake. For the optimization of WPC,
levels of 4, 6, 8, 10 g were used. With the increase in WPC from 4 to 10 g,
volume and weight of cakes increased significantly. But no changes in other
physical characteristic in cake. The cake made with WPC 6 g/ 100 g flour
was observed to have maximum score for overall acceptability.
Tripathy et al., (2003) studied that ragi (Finger millet) based products were
formulated utilizing whey protein concentrate (WPC) to enhance their
nutritional profile. WPC was used at 10 to 40% to replace ragi flour and the
products such as ragi malt and ragi dosa were prepared. The results revealed
that ragi malt and ragi dosa were best accepted at 30% level of WPC
supplement and had a protein content of 14.8 and 14.2% for ragi malt and
ragi dosa then compared to control.
Pawar et al., (2003) developed to enrich the nutritional quality of beverage
by adding whey protein concentrate (WPC) at 2, 3 and 4% levels. The
sensorial quality score of all the parameters reported comparatively higher in
case of beverage containing 3% WPC over that of other beverages. The
storage study of formulated WPC beverage reported 40 and 15 days as
active storage period at refrigerated (4 + 1°C) and room temperature (25 +
1°C) storage conditions without significant changes in nutritional and
sensory quality parameters. The unit cost of production of beverage
(300mL) worth of Rs. 7/- was observed to be comparatively higher because
of small scale production.
Gunasekaran (2003) observed that hydrogels made from WPC are pH-
sensitive with a minimum swelling ratio near the isoelectric point (pI) of
WPs (~5.1). These hydrogels are suitable for controlled drug release. The
swelling and release behavior of the WPC hydrogels can be controlled by
coating them with layers of calcium alginate. Beta-lactoglobulin (BLG), the
primary WP, can be used to prepare nanoparticles of about 60 nm average
diameter using desolvation method. The stability of the particles was
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investigated by degradation experiments at neutral and acidic conditions
with and without proteolytic enzymes.
Conforti and Lupano (2004) reported that the effects of honey, lemon
juice, and two different whey protein concentrates (WPC) on the structural
and functional properties of biscuits, were analyzed. The presence of WPC
with a high protein content produced a decrease in the firmness and
consistency and an increase in the cohesiveness of dough. Honey increased
the adhesiveness of dough, mainly in samples with the WPC of lower
protein content and lemon juice, and tended to decrease dough relaxation
time. The fracture stress of biscuits decreased with the incorporation of
WPC. Also, honey increased the red undertone and yellowness of biscuits
and decreased their lightness; however, the addition of lemon juice reduced
these effects.
Singh and Nath (2004) reported that protein enrichment of bael fruit
beverages was prepared by using partially denatured WPC complexed with
acidic polysaccharides i.e carboxymethyl cellulose (CMC) and pectin. A
beverages base with 25% bael fruit pulp, 16‘ brix and pH 3.9 was found
optimum and was fortified with 1.75, 2.75 and 3.75% level of WPC
polysaccharide complex. The products with 1.75% protein level of pectin
WPC complex and 1.75 and 2.75% protein level of CMC - WPC complex
were rated superior then other combinations. The beverages with 1.75%
whey protein level of CMC WPC complex scored maximum for all sensory
attributes.
Rai and Jayaprakasha (2004) reported that the spray dried sweet cream
butter milk (SCBM) was blended with spray dried WPC at various
properties along with other ingredients. Gulabjamun were prepared from the
mix developed by the various admixtures and compared with the control
samples. The results revealed that SCBM which had undergone a heat
treatment of 95 ˚C/ 20 min was highly suitable and instant gulabjamun mix
could be successfully prepared from an admixture of spray dried WPC and
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SCBM at 30:70 level without jeopardizing any of the functional and sensory
characteristics of the resulted gulabjamun.
Keskinler et al., (2004) observed that soluble whey proteins (WPs),
adsorbed on yeast cells, were recovered by a crossflow microfiltration (MF)
technique using a cellulose nitrate membrane with a pore size of 0.45 μm.
This technique not only provides for the recovery of protein but also may
give rise to the direct use of yeast cells, which are rich in protein, in the
baking industry. Whey protein absorbed by yeast cells can be used to
produce nutritionally rich products in areas where yeasts have been already
used.
Dewani and Jayaprakasha (2004) reported that replacement of milk solids-
not-fat (MSNF) up to 40% with WPC improved all the sensory attributes of
plain peda. They also applied RO process for pre-concentration of milk as an
intermediate step in the production of plain peda. It was concluded that such
product was nutritionally better than the conventionally made peda.
Salve et al., (2005) prepare low fat paneer from buffalo milk added with
Whey Protein Concentrate (WPC) at different levels. Paneer was prepared
from buffalo milk standardized to 6% fat and at lower fat levels viz, 5%, 4%
& 3%. Results revealed that the quality attributes of paneer differed
significantly with lowering of fat from 6% to 3% except appearance. The
sensory scores for body & texture and overall acceptability of paneer made
from buffalo milk with 4% fat and control paneer were comparable. Paneer
made from milk with 6% fat recorded highest yield as well as recovery of fat
and total solids. The product with 5% fat had almost similar recovery of
solids but with slightly low in yield. Incorporation of WPC at different
levels significantly influenced the sensory quality of low fat paneer. WPC @
2% was found most effective as compared to other levels for improving the
quality attributes of low fat paneer.
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Steinkraus (2005) suggested that soybean, green gram and Bengal gram can
bande substituted for black gram. Wheat or maize can be substituted for the
rice to yield Indian dhokla.
Alvarez et al., (2005) studied that two milk protein concentrates (MPC, 56
and 85%) as substitutes for 20 and 50% of the protein content in ice cream
mix. The basic mix formula had 12% fat, 11% non fat milk solids, 15%
sweetener and 0.3% stabilizer/emulsifier blend. Protein levels remained
constant, and total solids were compensated for in MPC mixes by the
addition of polydextrose. MPC formulations had higher mix viscosity, larger
amount of fat destabilization, narrower ice melting curves, and greater shape
retention compared with the control. MPC did not offer significant
modifications of ice cream physical properties on a constant protein basis
when substituted for up to 50% of the protein supplied by non fat dry milk.
Milk protein concentrates may offer ice cream manufacturers an alternative
source of milk solids non-fat, especially in mixes reduced in lactose or fat,
where higher milk solids non fat are needed to compensate other losses of
total solids.
Herrero and Requena (2006) stated that yoghurt was manufactured from
goat's milk and supplemented with 30 g L−1 of whey protein concentrate
(WPC). The addition of WPC to goat's milk enhanced the textural
characteristics of yoghurt. These advantageous attributes included increased
firmness, hardness and adhesiveness. These attributes were quantitatively
similar to those obtained from yoghurt made from cow's milk. In addition,
the textural properties were maintained constant throughout the shelf-life of
the product.
Prabha (2006) developed a technology for the production of dietetic burfi
using alternative ingredients, viz. whey protein concentrate (WPC), sorbitol,
maltodextrin and sucralose and optimized the ingredients using Response
Surface Methodology (RSM). The product was found to be highly
acceptable by the consumers.
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Gupta (2006) suggested that dairy ingredients are preferred ingredients due
to their functional suparmacy and good flavour, colour and nutritional
profile.
Perez (2006) studied that the effect of antioxidant and content alone or in
combination with edible coatings for fresh cut apples. Edible composite
coatings were prepared from WPC and beeswax (BW). Ascorbic acid at 0.5
and 1% content, cysteine at 0.1, 0.3 and 0.5% content and 4- hexylresorcinol
at 0.005 and 0.02% were incorporated in the formulations as antioxidants.
Result revealed that incorporation of the antioxidant to the coating reduced
browning compared to the use of the antioxidant alone.
Sodini et al., (2006) reported that two conditions of whey processing, pH
and heat treatment, affect the physical properties of stirred yoghurts fortified
to 45g protein kg -1 with whey protein concentrates (WPC). Cheddar whey
was heated at pH 6.4 or pH 5.8 at 72˚C for 15 s, eventually heated further at
82 or 88˚C for 78 s, ultra filtered and spray dried. Resulting WPC contained
38% protein, the denaturation level of the whey protein was 10 – 53%.
There were significant differences in physical properties of WPC fortified
yoghurts, water holding capacity ranged from 33% to 46% and elastic
modules ranged from 63 to 145 Pa depending on whey processing. WPC
with low denaturation level produced yoghurts with high elastic modules
and water holding capacity. Minimizing the heat treatment during whey
processing maximized the functional properties of WPC to be used in
yoghurt.
Patocka et al., (2006) examined that the addition of WPI up to 10%
decreased the apparent viscosity of a commercial yoghurt drink. The original
viscosity was restored at addition of 15% WPI. In buttermilk, minimum
viscosity was observed after addition of 6% and original value was restored
at 12%. Addition of the WPI was investigated either before fermentation
(BF) or after fermentation (AF) of the heated unfortified yoghurt milk.
Addition of WPI to commercial stirred yoghurt decreased G‘, while G‖ was
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affected only marginally. BF yoghurts behaved similarly to the commercial
yoghurt while AF yoghurt exhibited complete breakdown of the system.
Pinto et al., (2007) studied that low fat ice cream (LFIC) was prepared
containing WPC as a fat replacer. Addition of WPC in the LFIC is increased
in protein content and did not show any significant influence on pH and
acidity. It increased viscosity and whipping ability of the mixes and
increased in overrun, melting resistance and decreased firmness of hardened
product. The ice cream containing 1.25% WPC recorded better sensory
attributes compared to all the other samples. Addition of WPC above 1.25%
level resulted in a foamy, frothy, fluffy, slightly slimy/ sticky product.
Narender et al., (2007) studied that biscuits prepared from the blends
containing 10, 20 and 30% of whey protein concentrate (WPC). The protein
and ash contents of WPC containing biscuits were significantly higher then
the control. Blending of refined wheat flour with WPC up to 30% did not
have any adverse effect on the sensory quality of protein enriched biscuits.
The cutting and compression strengths of the 30% WPC incorporated
biscuits were significantly higher then the control. These protein enriched
biscuits can be stored for 60 days at ambient temperature (30- 35 ˚C).
Pinto et al., (2007) studied that blend of cheddar cheese comprising of 66%
of 2- 3 months old and 34% of 4- 5 months old cheddar cheese were used to
prepare processed cheese spread. Cheese solids were partially replaced by
WPC and solids at different levels viz. 1.5, 3.0 and 4.5 percent.
Incorporation of WPC resulted in a significant improvement in body and
texture score of spread particularly at 3.0 and 4.5% level. However, addition
of WPC at higher levels imparted a milder flavour to the product. Processed
cheese spread with good melt ability, desired characteristics with improved
spread ability can be prepared by using dried WPC at levels up to 4.5% of
cheese solids.
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Khillari et al., (2007) studied that incorporation of WPC replacing 20% fat
in ice cream mix (ICM) does not reduce in overrun and melting quality of
ice cream. Though, viscosity of ICM with increase in fat substitution by
WPC, the protein content of ice cream increased substantially but the
variations in carbohydrate and ash contents were negligible. Addition of
WPC substituting 20 to 40% fat is recommended for getting acceptable
quality low fat ice cream.
Prabhasankar et al., (2007) reported that effect of WPC (5%, 7.5%, 10%)
and additives on the quality of vermicelli made from Indian durum wheat.
Result revealed that with increase in WPC from 0% to 10% cooked
vermicelli weight increased from 82.5 to 88 g/25g cooking loss increased
from 6.0 to 8.4%, lightness increased (47.42 – 52.9) and yellowness
decreased (7.0 - 3.80) and shear force decreased (66 – 45g). Sensory
evaluation of vermicelli showed that addition of above 5% WPC resulted in
whitish colour vermicelli with mashy strand quality and sticky mouthfeel.
The effect of additives viz. ascorbic acid (0.01% and 0.015%), gluten (1.5%
and 3.0%) and glycerol monostearate (GSM) (0.25% and 0.5%) individually
as well as in combination on the quality of vermicelli with 5% WPC
indicated that combination of 0.01% ascorbic acid, 3% gluten and 0.5%
GSM resulted in vermicelli having lower cooking loss, creamy yellow
colour, firm, discrete strands and non-sticky mouthfeel.
Devaraju et al., (2008) reported that pasta were prepared by using finger
millet composite flour, the protein source are deffed soy flour and WPC.
Fortification of the protein content from 13.12 percent in control to 17.78
percent in pasta made from finger millet with composite flour sensory
evaluation scores indicated non significant difference among the control and
experimental products for texture.
Aziznia et al., (2008) studied that the effect of whey protein concentrate
(WPC) and gum tragacanth (GT) as fat replacers on the chemical, physical,
and microstructural properties of non fat yogurt. The WPC (7.5, 15, and
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20 g/L) and GT (0.25, 0.5, 0.75, and 1 g/L) were incorporated into the skim
milk slowly at 40 to 45°C with agitation. The yogurt mixes were pasteurized
at 90°C for 10 min, inoculated with 0.1% starter culture, and incubated at
42°C to pH 4.6, then refrigerated overnight at 5°C. A control non fat yogurt
and control full fat yogurt were prepared as described, but without addition
of WPC and GT. Increasing amount of WPC led to the increase in total
solids, total protein, acidity, and ash content, whereas GT did not affect
chemical parameters. No significant difference was observed for firmness
and syneresis of yogurt fortified with GT up to 0.5 g/L compared with
control non fat yogurt. Increasing the amount of gum above 0.5 g/L
produced softer gels with a greater tendency for syneresis than the ones
prepared without it. Addition of GT led to the coarser and more open
structure compared with control yogurt.
Lee and Vickers (2008) revealed that the acidity of whey protein solutions
was responsible for their astringency. Panelists rated acidic whey protein
and acid-only solutions for astringency and sourness. Acidic whey protein
solutions contained 6% or 1% whey protein isolate and phosphoric acid at a
pH of 3.4. Acid-only solutions were formulated to match the whey protein
solutions for either total acidity or for pH. The acid-only solutions matched
for total acidity were more astringent than the whey-containing solutions,
while those matched for pH were significantly less astringent. Sourness was
reduced by the whey proteins, most likely because of the decreased
concentration of free hydrogen ions. The astringency of acidic whey protein
solutions appears to be caused by their high acidity and not directly by the
whey proteins.
Beecher et al., (2008) studied that there are 2 types of whey protein-
containing beverages: those at neutral pH and those at low pH. Astringency
is very pronounced at low pH. Astringency is thought to be caused by
compounds in foods that bind with and precipitate salivary proteins. The pH
of the whey protein solution had a major effect on astringency. A pH 6.8
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whey protein beverage had a maximum astringency intensity of 1.2 (15-
point scale), whereas that of a pH 3.4 beverage was 8.8 (15-point scale).
Astringency decreased between pH 3.4 and 2.6, coinciding with an increase
in sourness. Decreases in astringency corresponded to decreases in protein
aggregation as observed by turbidity.
Lim et al., (2008) studied that three batches of low fat ice cream mix were
produced to contain WSU-WPC without high hydrostatic pressure (HHP),
WSU-WPC with HHP (300 MPa for 15 min), and WPC 35 without HHP.
All low fat ice cream mixes contained 10% WSU-WPC or WPC 35.
Overrun and foam stability of ice cream mixes were determined after
whipping for 15 min. The ice cream mix containing HHP-treated WSU-
WPC exhibited the greatest overrun and foam stability. Ice cream containing
HHP-treated WSU-WPC exhibited significantly greater hardness than ice
cream produced with untreated WSU-WPC or WPC 35. Improvements of
overrun and foam stability were observed when HHP-treated whey protein
was used at a concentration as low as 10% (wt/wt) in ice cream mix.
Seethalakshmi et al., (2010) stated that whey protein concentrate (WPC)
can be used as a replacer for egg in biscuit preparation. The addition of
whey protein concentrate (WPC) enhanced the nutritive value without
altering the sensory and physico chemical properties of biscuits. These
biscuits are more suitable for those do not consume egg and also for those
who need protein rich diet.
Mallasy et al., (2010) stated that supplementing pearl millet with whey
protein, samples and control were fermented in the presence of starter for
14 h. The pH, crude protein, in vitro protein digestibility (IVPD) and protein
fractions of the fermented and supplemented pearl millet were determined at
2- h intervals. Supplementation of whey protein resulted in significant
increase in protein content compared to the control. Fermentation was found
to cause a highly significant improvement in IVPD for AC, AW1 and AW2.
This would indicate an improvement in the nutritional quality of pearl millet.
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Sensory evaluation revealed higher acceptability for whey protein
supplemented formulas compared to control.
Baskaran et al., (2011) studied that the physical properties of noodles
enriched with skim milk powder, whey protein concentrate (WPC) and a
combination of skim milk powder and WPC at 5, 7.5 and 10% levels were
studied. Volume increase, weight increase and swelling ratio of the enriched
noodles were reduced at increasing levels of substitution. Total solids loss in
gruel showed increasing trend as the levels of substitution increased. It was
also found that, the loss of total solids was higher in noodles supplemented
with SMP compared to WPC and a combination of SMP and WPC.
Pintro et al., (2011) observed that whey protein ingredients were modified
to produce yoghurts with acceptable texture properties. Alteration of the
ratio of α-lactalbumin to β-lactoglobulin, heat denaturation and hydrolysis
treatments were applied to whey protein to improve their behaviour in
yoghurt formulations. Ingredients with increased proportion of α-
lactalbumin or made from partially hydrolyzed protein produced yoghurts
that closely matched the characteristics of control yoghurt. The effect of
whey protein ingredients on yoghurt rheological properties and dispersibility
was related to the concentrations of reactive thiol groups that determined the
extent of cross linking during acidification. During storage, yoghurt firmness
and viscosity increased and syneresis decreased. Yoghurt microstructure was
altered by whey protein ingredients, which significantly reduced void spaces
and increased gel matrix compactness.
Akalin et al., (2012) studied that the influence of milk protein-based
ingredients on the textural characteristics, sensory properties, and
microstructure of probiotic yogurt during a refrigerated storage period of 28
d. Milk was fortified with 2% (wt/vol) skim milk powder as control, 2%
(wt/vol) sodium calcium caseinate (SCaCN), 2% (wt/vol) whey protein
concentrate (WPC) or a blend of 1% (wt/vol) SCaCNand 1% (wt/vol) WPC.
The fortification with SCaCN improved the firmness, adhesiveness and
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higher values of viscosity in probiotic yogurts during storage. However,
WPC enhanced water-holding capacity more than the caseinate. Addition of
SCaCN resulted in a coarse, smooth, and more compact protein network;
however, WPC gave finer and bunched structures in the scanning electron
microscopy micrographs.
2.6 Nutritional aspects of whey protein concentrate (WPC)
Sandrou and Arvanitoyannis (2000) stated that low fat/ calorie products
were originally developed for diabetics and people with specific health
problems and they were considerably expensive. Now a days consumers
demand for low fat/ low calorie products have significantly risen in an
attempt to limit health problems to lose or stabilize their weight and to work
within the frame of healthier diets. The food industry has been confronted
with a new challenge in order to satisfy consumers by the development of
low fat/ calorie products with acceptable sensory characteristics and
competitive prices by preferably employing the conventional processing
equipment and in agreement with current strict legislations.
Tomar and Prasad (2002) reported that the dairy products as carries of
milk proteins and lactic acid bacteria are equipped with great potential in
prevention and cure of atherosclerosis and hypercholesterolemia.
Baker (2002) stated that there were some reductions in the incidence of
heart disease by eating low fat diets. He believed that one should increase
consumption of fruits and vegetables, olive oil, low fat dairy products and
fish oil to remain healthy and free from heart disease.
Kapoor (2007) observed that the fat intake in our diet occurs from two
sources, visible fat and invisible fat. It is easy to control the quality of visible
fat ingested. Most vegetarian foods contain intrinsically, a very low quantity
of fat except the whole milk and its products (nuts and seeds). It is easy to
separate out the milk fat and hence control the overall amount of fat eaten in
a vegetarian diet. For a vegetarian, the only source of animal fat is milk
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products. By using low fat milk and its products such as curd, cottage cheese
or paneer made from low fat milk, the vegetarian can minimize the amount
of animal fat ingested.
Madureira et al., (2010) suggested that processing of whey proteins yields
several bioactive peptides that can trigger physiological effects in the human
body: on the nervous system via their opiate and ileum-contracting
activities; on the cardiovascular system via their antithrombotic and
antihypertensive activities; on the immune system via their antimicrobial
and antiviral activities; and on the nutrition system via their digestibility and
hypocholesterolemic effects. The specific physiological effects, as well the
mechanisms by which they are achieved and the stabilities of the peptides
obtained from various whey fractions during their gastrointestinal route.
2.7 Cereal based fermented foods
Aliya and Geervani (1990) reported that as in other indigenous fermented
foods, a significant improvement in the biological value and net protein
utilisation of dhokla due to fermentation.
Chavan & Kadam (1990) suggested that the fermentation also leads to a
general improvement in the shelf life, texture, taste and aroma of the final
product. During cereal fermentations several volatile compounds are formed,
which contribute to a complex blend of flavours in the products.
Soni and Sandhu (1990) suggested that fermented foods are produced
world-wide using various manufacturing techniques, raw materials and
microorganisms. However, there are only four main fermentation processes:
alcoholic, lactic acid, acetic acid and alkali fermentation.
Purushothaman et al., (1993) reported that dhokla is also similar to idli
except that Bengal gram dhal is used instead of black gram dhal in its
preparation. A mixture of rice and chickpea flour is also used as the
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substrate for the fermentation. As in idli preparation, the fermented batter is
poured into a greased pie tin and steamed in an open steamer.
Battacharya and Bhat (1997) reported that dosa batter is prepared by
grinding wet rice and black gram separately with water. The two
suspensions are then mixed and allowed to undergo natural fermentation,
usually for 8–20 h. To make a dosa, the fermented suspension is spread in a
thin layer (of 1–5 mm thickness) on a flat heated plate, which is smeared
with a little oil or fat. A sol to gel transformation occurs during the heating
and within a few minutes, a circular, semi-soft to crisp product.
Simango (1997) stated that fermentation is one of the oldest and most
economical methods of producing and preserving food. In addition,
fermentation provides a natural way to destroy undesirable components and
enhance the nutritive value and appearance of the food and reduce the
energy required for cooking and to make a safer product.
Hirahara and Pagini (1998) suggested that the technologies for the
industrial production of fermented products from milk, fruit, vegetables,
cereals and meat are well developed and scientific work is actively carried
out all over the world.
Shukla et al., (2000) observed that biscuit along with bread form major
baked food produced in India accounting for over 30 and 50% of total
bakery products.
Shukla et al., (2000) stated that the per capita consumption of biscuit in
India is reported to be 8 kg per annum as against 15 kg per annum in
developed countries.
Manley (2001) reported that the protein fortified biscuits can be prepared
from composite flours such as wheat flour fortified with soy, cottonseed,
peanut, mustard or corn germ flour and also from vital wheat gluten and
milk powder.
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Samanth (2002) stated that India produces 3 million tonnes of bakery
products, which can be categorised into bread, biscuit and cake.
Puranik (2003) stated that bakery products are increasingly becoming
popular in India as indicated by over 2.5 fold increase in their production
during the last 2 decades.
Tyagi et al., (2007) stated that the protein fortified biscuits contain nutrients
in concentrated form useful for feeding programs at institutes such as day
care centres and schools or for emergency rations.
Riat and Sadana (2009) revealed that idli, dhokla, nan, kulcha, bread,
jalebi, bhatura, bhalla, dosa, gulgule and wadian were prepared in the
laboratory using traditional fermentation techniques. The fermented batter of
idli and dosa contained higher amount of available lysine, cystine and
methionine. After processing, maximum retention of lysine, methionine and
cystine was observed in steamed idli.
Kamble and Ghatge (2011) reported that soybased product such as
soyladoo was formulated in three different combinations with Bengal dhal
flour viz. 60:40, 50:50 and 40:60. Among these combinations was selected
and nutritionally evaluated on the basis of their storage stability. Due to
attractive colour, flavour, taste, appearance and overall acceptability of
soyladoo prepared with composition III i.e. use of soyflour 40g., with the
combination of Bengal gram dhal flour 60g. scored higher by
organoleptically. Chemical compositions like moisture, ash, crude protein,
iron, calcium zinc, carotene and vitamin B complex were found adequate in
this soyladoo.
Sharma et al., (2012) were examined the effect of blending level (0, 5, 10,
15 and 20%) of corn bran, defatted germ and gluten with wheat flour on the
physico-chemical properties, baking properties of bread, muffins and
cookies, and extrusion properties of noodles and extruded snacks prepared
from semolina. Breads from gluten blends had higher loaf volume as
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compared to bran and germ breads. Among corn byproducts, gluten cookies
were rated superior with respect to top grain. Muffins from germ blends and
gluten blends had higher acceptability scores than the bran muffins.
Blending of corn bran, defatted germ and gluten at 5 and 10% with wheat
flour resulted in satisfactory bread, cookie, and muffin score. Quality of
noodles was significantly influenced by addition of corn byproducts and
their levels. Acceptable extruded products (noodles and extruded snacks)
could be produced by blending corn byproducts with semolina up to 10%
level.
Ghosh and Chattopadhyay (2012) studied to use the method of
quantitative descriptive analysis (QDA) to describe the sensory attributes of
the fermented food products prepared with the incorporation of lactic
cultures. Panellists were evaluate to various attributes and acidity of the
fermented food products like cow milk curd and soymilk curd, idli,
sauerkraut and probiotic ice cream. Principal component analysis (PCA)
identified the six significant principal components that accounted for more
than 90% of the variance in the sensory attribute data. Overall product
quality was modelled as a function of principal components using multiple
least squares regression (R2 = 0.8). Further concluded that the utility of QDA
for identifying and measuring the fermented food product attributes that are
important for consumer acceptability.
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