Emulsifying and Foaming

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Emulsifying and foaming capacity and emulsion and foam stability of sesameprotein concentrates

Alicia Cano-Medina a, Hugo Jimnez-Islas b, Luc Dendooven c, Rosalba Patio Herrera a,Guillermo Gonzlez-Alatorre a, Eleazar M. Escamilla-Silva a,a Chemical Department, Instituto Tecnolgico de Celaya. Ave. Tecnolgico y A. Garca Cubas S/N. C.P. 38010. Celaya, Gto., Mexicob Biochemical Engineering Department, Instituto Tecnolgico de Celaya. Ave. Tecnolgico y A. Garca Cubas S/N. C.P. 38010. Celaya, Gto., Mexicoc Laboratory of Soils Ecology, Department of Biotechnology and Bioengineering, CINVESTAV, Ave. Instituto Politcnico Nacional 2508, A.P. 14740, C.P. 07360 Mxico D.F., Mexico

a b s t r a c ta r t i c l e i n f o

Article history:

Received 12 May 2010

Accepted 6 December 2010

Keywords:

Functional properties

Oil concentrations

pH

Production process

Sesame protein concentrate

Soybean protein concentrate

This study examined the effects of oil concentration and pH on the emulsifying and foaming characteristics of

sesame protein concentrate (SESPC). SESPC was obtained through a simplied process, and its properties

were compared with those of a commercial soybean concentrate (SOYPC). The simplied process did not

affect the functional characteristics of SESPC, which were often similar or superior to those of the SOYPC. The

maximum emulsifying capacity of SESPC was 38% at an acidic and alkaline pH, while the maximum

emulsifying capacity of SOYPC was 44% at the same pH . Emulsifying capacity increased signicantly as oil

concentration increased; in SESPC, this capacity increased from 7.8 to 60.0%, while in SOYPC it increased from

7.6 to 68.2%. The emulsion stability of SESPC was greater at an acidic pH (51%) than at an alkaline pH (45%); it

was also higher than the emulsion stability of SOYPC. The maximum emulsion stability of SESPC (96%) was

obtained at a sample concentration greater than 55 g L1 and oil concentration lees than 550 g L1 oil.

Minimum (118.3%) and maximum (240%) levels of SESPC foaming capacity were higher than those obtained

for SOYPC (92% as maximum). These ndings show that SESPC may have potential use as raw matter in the

food industry. At an extreme pH, SESPC continued to have important functional characteristics like emulsion

stability, oil absorption and foaming capacity.

2010 Elsevier Ltd. All rights reserved.

1. Introduction

Sesame seed (Sesamun indicum) has an oil content of between 48%

and 55%; as a result,it has become one of the main sources of edible oil.

It is also a good source of protein, yielding between 20% and25% protein

depending on the variety (Paredes-Lpez, Guzmn-Maldonado, &

Ordorica-Falomir, 1994). One of the principal characteristics of this

protein is its high methionine and tryptophan content. In fact, it is this

methionine content that distinguishes sesame from other oil seeds.

Sesame is, however, decient in lysine and isoleucine (Paredes-Lpez

et al., 1994). Sesame seed is important as a source of protein, but it has

some undesirable nutritional characteristics (as phytic acid); these

characteristics can be signicantly reduced when the hull is removed

(Shamanthaka-Sastry, Subramanian, & Parpia, 1974). Dehulled seeds

conserve signicant levels ofber (4.04.5%), phytic acid (more than

2.0%) and oxalic acid (more than 3.0%) (Paredes-Lpez et al., 1994;

Toma, Tabekhia, & Willians, 1979). These compounds have well-

documented negative effects on the nutritional and functional

properties of proteins and on the absorption of calcium, iron and zinc

present in the human diet; they must therefore be reduced or

eliminated (Cheryan, 1980; Frossard, Bucher, Machler, Mozafar, &

Hurrell, 2000).

Sesame proteins, while contributing to the nutritional value of

foods, can also be used as additives; their interesting functional

properties reect their physico-chemical characteristics, composition

and structure (Wagner & Gueguen, 1999; Autran, Halford, & Shewry,

2001; Bradley, 2002; Escamilla-Silva, Guzmn-Maldonado, Cano-

Medina, & Gonzlez-Alatorre, 2003). The sub-product of the oil

extraction process is sesame cake, whose protein content can reach

50%depending on the extraction method (Paredes-Lpez et al., 1994).

However, oil extraction processes also increase the content of

antinutritional components such as phytic acid, which increases

from 2% to 5%, and crude ber, which increases to 5.3%. Despite these

disadvantages, sesamecake hastraditionally been used as animal feed

due to its high content of quality protein (Little, van der Grinten,

Dwinger, Agyemang, & Kora, 1991). Attempts have been made to use

it as a source of protein for human consumption. We hypothesized

that the modication of some characteristics of sesame proteins could

improve its physicalchemical properties.

Emulsifying capacity (EC) and emulsion stability (ES) are two

important functional characteristics of proteins that affect the behavior

of various industrial products, including adhesives, cosmetics and

Food Research International 44 (2011) 684692

Corresponding author. Instituto Tecnolgico de Celaya, Dep. de Ingeniera Qumica,

Ave. Tecnolgico y Antonio Garca Cubas, CP.38010, Celaya Gto., Mexico.

E-mail address:[email protected](E.M. Escamilla-Silva).

0963-9969/$ see front matter 2010 Elsevier Ltd. All rights reserved.

doi:10.1016/j.foodres.2010.12.015

Contents lists available at ScienceDirect

Food Research International

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packing material (Hettiarachy & Kalapathy, 1998; Wagner & Gueguen,

1999). Sesame proteins are a by-product of these industrial processes.

Because the extraction process is inexpensive, the protein concentrate

has an attractive and economic cost.

EC and ES are critical parameters that affect the choice of a protein

for use in an industrial process. Proteins can reduce tension at the

wateroil interface and help prevent coalescence (McWatters &

Cherry, 1981). A protein'sstabilizingeffect in an emulsion comes from

the membrane matrix that surrounds the oil drop and prevents itscoalescence (Jones, 1984).

Another practical application of proteins in industrial production

comes from their ability to generate foam. Foaming capacity (FC) and

foam stability (FS) are importantparameters in the characterization of

the functional properties of proteins. Proteins must be highly soluble

in water, exible and form part of a cohesive lm at the waterair

interface to ensure good foam formation (Wagner & Gueguen, 1999).

The lm should possess sufcient viscosity to maintain stability and

prevent rupture and subsequent coalescence. Lipids are the main

cause of destabilization of the foam from protein concentrates and

isolates. Studies have shown that the removal of neutral lipids with

hexane and of polar lipids with aqueous alcohol leads to a marked

increase in the foaming properties of soybean proteins. In addition,

the foaming properties of these proteins increase when the product is

heated to 7580 C. Although soybean proteins have a good foaming

capacity after both heating and the extraction of lipids, the practical

applications of these proteins are still limited by their structural

instability (i.e., the rupture of hydrogen and disulphide bonds)

(Hutton & Campbell, 1977; Inyang & Nwadimkpa, 1992).

Sesame proteins can add avor to foams, emulsions and gels used

in a many food products. There is therefore continued interest in

improving the functional properties of sesame proteins to ensure

attractive products (Escamilla-Silva et al., 2003). One way to increase

the functional properties of a protein is to determine its origin and

concentration as well as the mechanical forces used for its extraction

(Hutton & Campbell, 1977). Additionally, the effect of drying

conditions on the functional properties of protein concentrates and

isolates must be investigated (Gueguen & Cerletti, 1994). Drum

drying, as opposed to spray and freeze drying, increases theemulsifyingcapacityof pea, fava bean and soybean proteins (Gueguen

& Cerletti, 1994). An increase in drying temperature from 50 C to

98 C, however, gradually reduces the solubility and emulsifying

properties of proteins. Most of the variation in functional properties is

related to modications of protein structure that result from

processing conditions.

The objective of the present work was to study the EC, ES, FC and

FS of sesame protein concentrate (SESPC). The SESPC was obtained

with a simplied method in which the product of an alkaline

extraction did not undergo isoelectric precipitation or protein

neutralization (Escamilla-Silva et al., 2003).This study examined the

effects of SESPC concentration, oil concentration and pH on EC and ES;

while SESPC concentration and pH on FC and FS. These properties

were compared with those of a commercial soybean proteinconcentrate (SOYPC).

2. Materials and methods

2.1. Proteins

Sesame meal (b1% oil), made from defatted and mechanically

dehulled seed, was obtained from DIPASA, Mexico, a local company

specializing in oil production. Theproteins were obtained from defatted

sesame meal through alkaline extraction at pH 9 at a 1:10 (w/v) meal:

water ratio at room temperature. The extraction mixture was ltered

and a protein-rich aqueous solution was recovered. The SESPC was

obtained by a simplied process, i.e., direct spray-drying of the protein-

rich aqueous solution without isoelectric precipitation and neutraliza-

tion (Escamilla-Silva et al., 2003;Hutton & Campbell, 1977).A soybean

protein concentrate was obtained from a local business (FABSA,

Mexico) so the functional characteristics of the sesame protein

concentrate could be compared with those of a commercial product.

2.2. Emulsifying capacity and emulsion stability

The EC of SESPC and SOYPC were measured according to the

method described byWang and Kinsella (1976). Aqueous dispersionsof25,50 and 75 g L1 of both products were prepared andadjusted to

pH 4.5, 7.0, and 9.5 with 0.01 M HCl or NaOH. The dispersions were

blended at high speed (10,000 rpm) while corn oil was poured into

the blender at aow rate of 1 mL s1.The nal concentration of oil in

each sample was 50, 200, 400, and 550 g kg1. After agitation, the

samples were centrifuged at 5000 rpm for 5 min in a Gallenkamp

centrifuge. The EC was expressed as:

EC % =Height of the emulsified layer cm

Totalheight cm 100:

A similar procedure was followed to determine the ES, but the

samples were incubated at 80 C for 30 min before centrifugation. The

ES was calculated with the same formula.

2.3. Foaming capacity and foam stability

The method described byTsutsui (1988)was used to determine

the FC and FS of SESPC and SOYPC. Solutions of SESPC and SOYPC were

prepared at 5, 20, 30, and 45 g L1, and pH was adjusted to 2.0, 5.0,

7.0, 8.5 and 10 with 0.01 M HCl or NaOH. The solutions were agitated

in graduated plastic tubes at high speed in an Oster blender for 1 min.

Foam capacity was reported as:

FC % =Volume after agitation volume prior to agitation

Volume prior to agitation 100:

A similar procedure was used to determine the FS, but the samples

were allowed to stand for 30 min at room temperature and theresidual foam volume was measured. The following formula was used

to calculate FS:

FS% =Residual foam volume

Totalfoam volume 100:

2.4. Statistical analyses

Response surface methodology was used to analyze the range and

intervals of the experimental parameters. Data analysis and graphic

plotting were done with STATISTICA software (tatsoft, 1995).

Quadratic models were used to create 3-dimensional response surfaces.

In response surfaces, independent variables are located along the X andY axes, while the response variable is located along the Z axis per-

pendicular to the XY axes. Analysis of variance and least signicant

differences were used to analyze for signicant differences at the 5%

level between treatments. The Steel and Torrie (1982) method of

regression analysis was used for simple regression models.

3. Results and discussion

3.1. Emulsifying capacity

Fig. 1 shows the response surface interaction between pH and

SESPC and SOYPC reected the interdependent effects of these two

factors on emulsifying capacity (EC) at oil concentration of 550 g L1.

The maximum EC for SESPC (38.0%) was found in the range of 40 to

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65g L1 protein concentrate and a pH of more than 9.0 or less than 5.0

(Fig. 1a). The lowest EC (19.2%) was found at lower SESPC concentra-

tions and in a pH range between 4.6 and 6.8 (b0.05). This decreasewas the result of the low solubility of the protein when its isoelectric

point of 5.0 is reached (Escamilla-Silva et al., 2003). Protein solubility is

known to directly affect theEC of a protein (Paredes-Lpez et al., 1994).

The isoelectric point changes with the ambient ionic strength of the

solution so that the potential Z tends to zero (i.e., Coulombic forces

cause the molecules to be more stable and the Brownian movement

facilitates the formation suspensions rather than emulsions). As shown

in Fig. 1a, the SESPC concentration increased for the same pH range. The

EC level also increased, supporting the previously-described theory.

The response area of the interaction between the SOYPC

concentration and pH shows that EC increased signicantly from

8.5% to 40.1% when pH increased (b0.05) (Fig. 1b).Wang and Zayas

(1992)observed a similar behavior with soybean protein. However,

they reported larger EC percentages (70

105%) than those observed

in this research. These differences could be due to the difference in

products and/or the process by which the SOYPC was obtained.

Moure, Sineiro, Dominguez, and Parajo (2006) report a proteinsolubility of 97 mg mL1 and 36100 mg mL1 for sesame and

soybean, respectively. These values explains the similar magnitude

of EC both SESPC and SOYPC, The protein solubility exhibits a

minimum value at isoelectric point, originating that surface tensions

of wheat proteins were lowest. (Kinsella, 1981;Escamilla-Silva et al.,

2003; Alfaro, Alvarez, Khor, & Padilla, 2004). The concentration of

SOYPC affected EC less than pH. Below pH 6, the EC of the protein

concentrate increased when the SOYPC concentration increased.

Above pH 6, however, this effect was not as strong.

This study also examined the effect of oil concentration for SESPC

and SOYPC. EC increased signicantly when oil concentration

increased (b0.05) as shown inFig. 2at pH 7. EC reached a maximum

of 60% when SESPC concentration was more than 45 g L1 and oil

concentration was morethan 500 g L1

(Fig.2a). SESPC concentration

Fig. 1.The emulsifying capacity (%) as affected by sample concentration and pH for a) sesame protein concentrate (SESPC) and b) commercial soybean concentrate (SOYPC) at oil

concentration of 550 g L1.

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did not affect EC as much as the presence of oil. EC reached a

maximum of 68.2% when SOYPC concentration was more than

70 g L1

and oil concentration was more than 500 g L1

. ECdecreased as oil concentration decreased (Fig. 2b). The maximum

EC percentages found in this study were similar to those reported by

Marcone and Kakuda (1999). They found that the EC of soybean

globulins did not exceed 58%. EC values were very similar for SESPC

and SOYPC at the oil concentrations and pH levels studied. Therefore,

SESPC can be substituted SOYPC at an acidic pH. Table 1 shows

quadratic models that present the best conditions for SESPC EC and

SOYPC EC as a function of pH of the medium (P), concentration of

SESPC or SOYPC (Q), and concentration of oil (S).

3.2. Emulsion stability

Fig. 3 depicts the effect of pH and sample concentration on

emulsion stability at oil concentration of 550 g L1

. The response

surface interaction between SESPC concentration and pH showed that

ES was greater at acidic (50.6%) pH levels than at basic (44.8%) pH

levels for larger SESPC concentrations (Fig. 3a). As pH approached a

Fig. 2.The emulsifying capacity (%) as affected by sample concentration and the amount of oil (g L1) for a) sesame protein concentrate (SESPC) and b) commercial soybean

concentrate (SOYPC) at pH 7.

Table 1

Response surface of the form Z1= a + a1P +a2Q +a3P2+a4PQ+a5Q

2 for emulsifying

capacity of SESPC and SOYPC.

I a a1P a2Q a3P2 a4PQ a5Q

2 R2

Z1 26.687 0.679 23.397 0.356 0.814 1.65 0.975

Z2 19.733 3.246 2.999 0.468 0.831 0.401 0.978

I a a1S a2Q a3S2 a4SQ a5Q

2 R2

Z3 16.747 0.545 8.349 0.003 0.053 0.804 0.984

Z4 49.720 0.318 17.309 0.006 0.151 1.472 0.975

Z1and Z3the EC of SESPC and Z2and Z4the EC of SOYPC; P = pH of the medium; Q =

the concentration of SESPC or SOYPC (%); and S = concentration of oil (%).

The models were resolved using a 95% condence interval.

http://localhost/var/www/apps/conversion/tmp/scratch_2/image%20of%20Fig.%E0%B2%80


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neutral value, the ES gradually decreased, and the lowest value of

35.6% was found at lower SESPC concentrations. The concentration of

SESPC had a smaller effect on ES than pH.

The response surface interaction between SOYPC concentration

and pH showed that the maximum ES value (39.0%) was found at pHlevels over 5 and with SOYPC concentrations of 2560 g L1 (Fig. 3b).

The ES value of SOYPC was signicantly lower than that of SESPC

(b0.05). As pH approached a neutral value, the ES dropped for the

entire concentration range of SOYPC studied. At SOYPC concentrations

less than 30 g L1 and more than 65 g L1, the ES values were under

15.5% for the 5.5 to 9.0 pH range (Fig. 3b). In general, the ES of SESPC

was greater than that of SOYPC for the entire pH and concentration

range studied.

Fig. 4depicts the effect of sample concentration and oil concentra-

tion on emulsion stability at pH 7. The effect of the interaction between

SESPC concentration and oil concentration showed that ES was not

affected signicantly by the SESPC concentration (Fig. 4a). The

minimum ES value was found with an oil concentration ranging from

150 to 350 g L1

; ES increased when the oil concentration increased or

decreased. The largest ES value (96%) was obtained at SESPC

concentrations of more than 55 g L1 and less than 530 g L1 oil. The

ES of SOYPC was less stable than that of SESPC. The maximum ES value

(56%) occurred at an oil concentration of approximately 550 g L1 and

at a SOYPC concentration of less than 55 g L1

(Fig. 4b). The maximumES value of SOYPC (56%) was signicantly lower than that of SESPC

(96%) (b0.05). The SOYPC also reached much lower ES values (8.4%)

than the SESPC for oil concentrations between 150and 400 g L1 and at

SOYPC concentrations b 27 g L1 or N60g L1.

In all interactions, SOYPC had lower ES values than SESPC; these

results are similar to those reported by Konishi and Yoshimoto

(1987). These authors found that the ES of amaranth proteins were

almost double that of soybean proteins, especially at basic and acidic

pH levels.Marcone and Kakuda (1999)found that even in the region

of the isoelectric point, amaranth globulins showed greater EC and ES

than soybean globulins.

SESPC behavior at acidic and basic pH levels could reect the

presence of hydrophobic residues and the denaturalization or partial

unfolding of the globular protein caused by the change in pH(Sze-Tao

Fig. 3.The emulsion stability (%) as affected by sample concentration and pH for a) sesame protein concentrate (SESPC) and b) commercial soybean concentrate (SOYPC) at oil

concentration of 550 g L1.



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& Sathe, 2000). This process exposes a greater hydrophobic surface

that gives greater mobility at the interface and improves the

penetration of the aqueous phase to the native structure (Konishi &

Yoshimoto, 1987; Pandya et al., 2000; Schwenke, 2001; Deng et al.,2011). Table 2 shows quadratic models expressing the best conditions

for the ES of SESPC and SOYPC as a function of P, Q and S.

3.3. Foaming capacity

The response surface showed that both the SESPC concentration

and the pH signicantly affected FC (Fig. 5a). As the SESPC

concentration increased and the pH decreased, the FC increased. The

maximum FC value observed for SESPC was 240% at a pH less than 5

and SESPC concentrations more than 40 g L1. This FC level was 2.5-

times greater (b0.05) than the maximum value found for SOYPC

(Fig. 5b). The maximum FC level of the SOYPC was around 92% at a pH

near to 10 and a protein concentrate levels above 40 g L1 (Fig. 5b).

The FC levels of SOYPC were lower than those of SESPC over the pH

range and concentration tested for. As the pH decreased towards the

isoelectric point for SOYPC, the FC also decreased more accentuated

when the SOYPC concentration increased. The same tendency was

observed at low SOYPC concentrations and basic pH. The SESPC

Fig. 4. The emulsion stability (%) as affected by sample concentration and the amount of oil (g L1) for a) sesame protein concentrate (SESPC) and b) commercial soybean

concentrate (SOYPC) at pH 7.

Table 2


2 for emulsion

stability of SESPC and SOYPC in function of P, Q and Z.


2 R2

Z7 124.736 2 5.71 3 2.07 2 1.72 4 0.04 6 0.155 0.981

Z8 125.990 38.683 16.203 2.467 0.543 2.145 0.9920.992

I a a1S a2Q a3S2 a4SQ a5Q

2 R2

Z9 90.634 4.333 7.571 0.076 0.069 0.726 0.963

Z10 12.401 1.592 20.1148 0.043 0.0941 1.825 0.975

Z7and Z9the ES of SESPC and Z8and Z10the ES of SOYPC; P = pH of the medium; Q =

the concentration of SESPC or SOYPC (%); and S = concentration of oil (%).

The models were resolved using a 95% con

dence interval.



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obtained by the simplied method has characteristics that could be of

great industrial interest. The best conditions for FC of SESPC and

SOYPC in function of P and Q as expressed with quadratic models are

presented in theTable 3.

3.4. Foam stability

The response surface interaction between SESPC concentration

and pH showed that both affected FS (Fig. 6a). FS increased when SESPC

concentration increased and pH decreased. The minimum FS value

(50.4%) was obtained at a pH above 7.6 and a SESPC concentration of

less than 10 g L1. The maximum FS of SESPC (94%) was obtained at

SESPC concentrations of more than 42 g L1 and pH values under 2.5.

The FS of SOYPC increased to a maximum of 110% at SOYPC

concentrations below 24 g L1 and in a pH range of 3.57.6. At a pH

above 7.6, the FS of SOYPC decreased (Fig. 6b).

The highest FS of SESPC (110%) was signicantly greater than the

maximum FS for SOYPC (94%) (b0.05) (Fig. 6). SOYPC also showed

much lower FS values (15.6%) (b0.05) than SESPC, especially below

pH 3.0 and at a SOYPC concentration of more than 32 g L1

.

Table 4shows quadratic models expressing the best conditions for

the FS of SESPC and SOYPC as a function of P and Q.

A greater amount of SESPC than SOYPC was required to obtain

similar FS levels. However, SESPC can be used under a wider range of

pH conditions than SOYPC; this characteristic makes SESPC more

versatile. It would be worthwhile to study the behavior of SESPC atconcentrations of more than 45 g L1, as theresponsesurface showed

a tendency of concentration to increase theFS. It wasfound that theFS

of SESPC was directly related to its FC; when FS increased so did FC

Fig. 5.The foaming capacity (%) as affected by sample concentration and pH for a) sesame protein concentrate (SESPC) and b) commercial soybean concentrate (SOYPC).

Table 3

Response surface of the form Z1= a + a1P +a2Q+ a3P2+a4PQ+a5Q

2 for foaming

capacity of SESPC and SOYPC in function of P, Q and Z.


2 R2

Z11 142.034 4.387 13.842 0.797 0 .70 5 2 .0 63 0 .98 9

Z12 83.266 6.736 13.075 0.015 2.717 0.291 0.992

Z11 the FC of SESPC and Z12 the FC of SOYPC; P = pH of the medium; Q = the

concentration of SESPC or SOYPC (%).




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(Figs. 5a and6a). This tendency did not occur with SOYPC (Figs. 5b

and6b).

The FC and FS of SESPC increased when its concentration increased

at a lower pH. These results are different from those reported byAoki

et al. (1999). They reported that the FC of ovalbumin tended todecrease when the isoelectric point was reached. In our study, protein

solubility tended to decrease when the isoelectric point was reached;

this protein solubility in turn affected the FC of the protein. Protein

solubility reached its lowest value (Escamilla-Silva et al., 2003) when

the pH of SESPC reached its isoelectric pH (5.0); FC and FS, however,

increased at this point (Figs. 5a and6a).

The FC of SESPC showed the same behavior reported by Aoki et al.

(1999). It decreased when the pH reached its isoelectric point

(Fig. 5b). Nevertheless, the FS of SOYPC increased as the pH increased.This nding contradicts the results reported by Matsudomi, Sasaki,

Kato, and Kobayashi (1985). They reported that the FC of SOYPC

increased when the pH decreased.

4. Conclusions

The high EC found as function of protein concentration and oil

concentration at basic pH levels could indicate SESPC and SOYPC

globulin content (75.8% and 90%, respectively, Escamilla-Silva et al.,

2003). This was in agreement with the general correlation between

emulsion properties and protein solubility (Marcone & Kakuda, 1999;

Deng et al., 2011) It has been reported that soy globulins show larger

EC properties at basic pH levels than at acidic levels (Gueguen &

Cerletti, 1994). One possible explanation for the increase in FC and FS

Fig. 6.The foaming stability (%) as affected by sample concentration and pH for a) sesame protein concentrate (SESPC) and b) commercial soybean concentrate (SOYPC).

Table 4


2 for foam stability

of SESPC and SOYPC in function of P, Q and Z.


2 R2

Z13 119.9 13.025 6.180 0.625 0.93 1.25 0.973

Z14 3 4.931 25.039 0.854 2.173 1.357 4.268 0.985

Z13 the FS of SESPC and Z14 the FS of SOYPC; P = pH of the medium; Q = the

concentration of SESPC or SOYPC (%).




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of SESPC as pH decreased because the net charge is near minimum in

the isoelectric region that induces to protein might have aggregated

and destabilized the interfacial membrane (Inyang & Iduh, 1996). This

reduced stability is why we are currently seeking to modify proteins

to improve foam stability. In addition, some nutritional products

require proteins that generate foam; increased form stability could

allow for additional uses of the sesame protein (Moure et al., 2006).

The presence of phytic acid in SESPC is also important; at certain

concentrations phytic acid could affect the functional propertiesstudied in this work (Rahama, Duek, Mothes, Gornitz, & Schwenke,

2000).

The simplied process used in the production of SESPC did not

affect the functional properties studied. These properties (e.g., ES)

were often similar or superior to those of SOYPC. In addition, SESPC

may ultimately be more versatile; at the extreme pH levels found in a

variety of food and/or industrial products, SESPC showed important

EC, ES, FC and FS characteristics.

Acknowledgements

We thank A. Williams for revising the English of the manuscript.

This research was funded by Consejo del Sistema Nacional de

Educacin Tecnolgica (COSNET) grants 581.01-PA and 290.90.

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Emulsifying and Foaming