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STUDIES ON PRESERVATION AND PROCESSING OF CUSTARD APPLE (Annona squamosa L.) PULP
By
T. SRAVANTHI B.Sc (Food Science)
THESIS SUBMITTED TO ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF
MASTER OF FOOD SCIENCE TECHNOLOGY
INTERFACULTY PG PROGRAMME
POST GRADUATE AND RESEARCH CENTRE ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
RAJENDRANAGAR, HYDERABAD – 500 030
MARCH, 2004
STUDIES ON THE PREPARATION OF SQUASH, NECTAR, RTS AND JUICE BLENDS FROM
WATERMELON FRUITS
By
FATHIMA FARHEEN B.Sc.
THESIS SUBMITTED TO ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF
MASTER OF FOOD SCIENCE AND TECHNOLOGY
INTERFACULTY PG PROGRAMME
POST GRADUATE AND RESEARCH CENTRE ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
RAJENDRANAGAR, HYDERABAD – 500 030
APRIL, 2004
CERTIFICATE
I, T. SRAVANTHI has satisfactorily prosecuted the course of
research and that the thesis entitled “STUDIES ON PRESERVATION
AND PROCESSING OF CUSTARD APPLE (Annona squamosa L.)
PULP” submitted is the result of original research work and is of
sufficiently high standard to warrant its presentation to the examination.
I also certify that the thesis or part thereof has not been previously
submitted by her for a degree of any university.
Date : (Dr. Y. NARAYANA REDDY) Place : Hyderabad Major Advisor
CERTIFICATE This is to certify that the thesis entitled “STUDIES ON PRESERVATION AND PROCESSING OF CUSTARD APPLE (Annona squamosa L.) PULP” submitted in partial fulfillment of the requirements for the degree of MASTER OF FOOD SCIENCE AND TECHNOLOGY of the Acharya N.G. Ranga Agricultural University, Hyderabad, is a record of the bonafide research work carried out by T. SRAVANTHI under our guidance and supervision. The subject of the thesis has been approved by the student’s advisory committee. No part of the thesis has been submitted for any other degree or diploma. The published part has been fully acknowledged. All assistance and help received during the course of the investigation have been duly acknowledged by the author of the thesis.
(Dr. Y. NARAYANA REDDY) Chairman of the Advisory Committee
Thesis approved by the student advisory committee Chairman (Dr. Y. NARAYANA REDDY)
Professor and Univ. Head, Department of Horticulture, Rajendranagar, Hyderabad-30.
Member
(Dr. J. DILIP BABU) Senior Scientist, AICRP on PHT, Rajendranagar, Hyderabad-30.
Member
(Dr. R. SUBHASH REDDY) Associate Professor and Univ. Head Department of Agricultural Microbiology and Bioenergy, Rajendranagar, Hyderabad-30.
Member (Dr. S. SUMATHI) Associate Professor, Post Graduate Research Centre Rajendranagar, Hyderabad-30.
DECLARATION
I, T. SRAVANTHI hereby declare that the thesis entitled
“STUDIES ON PRESERVATION AND PROCESSING OF CUSTARD APPLE
(Annona squamosa L.) PULP” submitted to the ACHARYA N.G.
RANGA AGRICULTURAL UNIVERSITY for the degree of
MASTER OF FOOD SCIENCE AND TECHNOLOGY is the result
of original research work done by me. I also declare that any material
contained in the thesis has not been published earlier.
Date : (T. SRAVANTHI)
CONTENTS
Chapter
Title
Page No.
I INTRODUCTION
II REVIEW OF LITERATURE
III MATERIALS AND METHODS
IV RESULTS
V DISCUSSION
VI SUMMARY
LITERATURE CITED
APPENDICES
ABBREVATIONS
RTS - Ready to serve
TTS - Total soluble solids
SO2 - Sulphurdioxide
ppm - Parts per million
N - Normality
NaoH - Sodium hydroxide
HCl - Hydrochloric acid
TPC - Total plate count
ANOVA - Analysis of variance
F.P.O. Specifications
Squash Minimum % of TSS in final
product (w/w)
40
Nectar Minimum % of TSS in final
product (w/w)
15
RTS - Minimum % of TSS in final
product (w/w)
10
Permissible limits of preservatives
Squashes SO2 350 ppm
RTS SO2 100 ppm
Pulp SO2 1000 ppm
SCORE CARD Name of the evaluator: Date : Time : You are requested to evaluate the products prepared with water melon for the following sensory attributes as per the guidelines indicated below.
Attributes 1 2 3 4 5 6
Appearance
Color
Flavour
Taste
Overall acceptability
Comments / suggestions :
Signature of evaluator
Scores : Excellent : 5 Good : 4 Fair : 3 Poor : 2 Very poor : 1
S. No. List of tables Page No.
1. Physico-chemical characteristics of custard apple pulp and its products before storage
2. Organoleptic characteristics of custard apple products before storage
3. Microbiological characteristics of custard apple pulp and its products before storage
4. pH of processed custard apple products
5. Total soluble solids of custard apple products
6. Acidity of custard apple products
7. Ascorbic acid of custard apple products
8. Sulphur dioxide of custard apple products
9. Reducing sugars of custard apple products
10. Total sugars of custard apple products
11. Appearance of custard apple products
12. Colour of custard apple products
13. Flavour of custard apple products
14. Taste of custard apple products
15. Overall acceptability of custard apple products
16. Total plate count of custard apple products
17. Yeast and mould count of custard apple products
S. No. List of plates Page No.
1. Products prepared from stored custard apple
pulp
2. Squash, nectar and RTS
3. Toffee
4. Products from stored custard apple pulp
5. Custard apple products after four months
storage
S. No. List of Figures Page No.
1. pH of stored custard apple products
2. Total soluble solids of stored custard apple
products
3. Acidity of stored custard apple products
4. Ascorbic acid of stored custard apple products
5. Sulphurdioxide of stored custard apple
products
6. Reducing sugars of stored custard apple
products
7. Total sugars of stored custard apple products
Acknowledgements It is due to the blessings of Shirdi Sai that I have been able to complete my studies successfully hitherto and present this piece of work for which I am eternally debated. Accompliments of this thesis is the result of benevolence of His divine grace. I am pleased to place my profound etiquette and indebtedness to my major guide Dr. Y. Narayana Reddy for suggesting the research work, for the unstincted attention, arduous and meticulous guidance given through out my research investigation despite of his hectic academic schedule. I extol the genuine cooperation and inspiration given to me right from the initiation of work to ship shaping of the manuscript. It was indeed a real privilege for me to work under his unending inspiration and undomitable spirit. I fervently and modestly thank Dr. J. Dilip Babu, member of my advisory committee for his guidance and help provided during my investigation. Ineffable is my gratitude and sincere thanks to Dr. Subhash Reddy, member of the advisory committee for his support during my research work. I humbly offer my sincere thanks to Dr. Sumathi, member of the advisory committee for her guidance and encouragement offered during my course work. I owe my flow of thanks to Dr. Deva muni Reddy and Naram Naidu for their guidance offered during my course work. I owe an encompassing debt to my most beloved parents Ram Reddy and Roja and my grand mother Kousalya who taught me the concept of life. They have constantly inspired, educated, guided and molded into the present situation and whose encouragement brings out my best in each one of my endeavors. There is no match to the affection and co-operation given to me by my brothers Sravan, Rahul, Rajeev and cousin Deepthi. It is with love, I wish to place or record the unbounded affection, cheerful encouragement and co-operation extended to me by my beloved husband Kodanda Rama Reddy during my research work. I accolade my highest respects to my beloved in-laws for their affection and blessings, which helped me to move successfully.
Diction is not enough to express my deep sense of gratitude and affection for my ever loving friends Krishnalatha, Himabindu, Srividya and Sunanda who had always showed me their everlasting affection, co-operation and lovely company. The fond memories of the time spent with them are going to be cherished forever by me. It is time to surface out my affection and genuflect love to my colleagues Vijayabhanu, Ramesh, Radha, Yellamanda, Farheen, Ramana, Sudheer, Soujanya, Vinoothna and Smitha. Who made my college life a memorable one. A special word of thanks to all my juniors for their alacrity and support. Lastly I wish to extend my thanks to one and all who contributed even in a small way in the completion of my research work Date:
T.Sravanthi
Name of the Author : T. SRAVANTHI
Title of the Thesis : “STUDIES ON PRESERVATION AND
PROCESSING OF CUSTARD APPLE (Annona squamosa L.) PULP”
Degree to which it is submitted
: MASTER OF FOOD SCIENCE AND TECHNOLOGY
Faculty : Inter faculty P.G. Programme
Department : Post graduate and research center
Major Advisor : DR. Y. NARAYANA REDDY
University : Acharya N.G. Ranga Agricultural University, Rajendranagar, Hyderabad-30.
Year of submission : 2004
ABSTRACT
Custard apple is one of the important fruit crops of Andhra Pradesh, which ripen within four days after harvest. Considering the fast increasing area under custard apple cultivation, methods of its preservation and processing technology needs to be developed to regulate the prices of produce during glut period.
Pulp was extracted from custard apples and stored for a period of
six months by addition of 1500 ppm of potassium metabisulphite. After six months, various products like squash, nectar, ready-to-serve beverage (RTS) and toffee were prepared.
The products were stored at room temperature and cold storage
for a period of four months to study the stability and consumer acceptability of the products. The products were analysed every month for physico-chemical and organoleptic qualities. The microbiological safety of these products was also evaluated.
The pH, acidity, ascorbic acid and sulphurdioxide were lower in
all the products compared to the stored pulp whereas, TSS, reducing and total sugars were high. Microbial count was negligible and E. coli were completely absent on all the products. The products ranked excellent in all organoleptic qualities.
All the products stored at cold storage were good physico-
chemically, microbiologically and organoleptically when compared to the products stored at room temperature.
pH and TSS were found to be more in products stored at cold
storage compared to room temperature. Acidity of squash and nectar stored at cold storage was more than that at room temperature. Ascorbic acid retention was more in squash and nectar stored at cold storage but a decrease was observed in RTS and toffee. SO2 was more in all the products stored at cold storage. Squash and nectar stored at cold storage were found to have more reducing and total sugars than that stored at room temperature. There was a decrease in reducing and total sugars in RTS and toffee stored at cold storage. The products stored at room temperature were accepted till third month of storage whereas, the products stored at cold storage showed an over all acceptability upto four months of storage. Increase in microbial growth with storage period was observed in all the products but the increase was more in the products stored at room temperature to that at cold storage.
The acceptability of the products decreased gradually with
increase in storage time. The pH and TSS of all the products decreased upon storage. Acidity of all the products increased with increase in storage period. In squash, nectar and toffee ascorbic acid content increased with the storage period. SO2 and reducing sugars of all the products decreased with the storage period. There was an increase in total sugars in squash and toffee with increase in storage period but total sugars reduced in RTS and nectar upon storage. The results showed that the products can well be stored for at least four months without deterioration preferably at cold storage.
CHAPTER – I
INTRODUCTION
Custard apple, (Annona squamosa L.) is one of the important fruit
crops of Andhra pradesh. Nearly, 75,000 tonnes of this fruit is available
from the state. Custard apple is a hardy crop, which can be grown on
marginal lands with minimum inputs. Custard apple, popularly known as
sharifa or sitaphal is grown in about 40,000 ha in India mainly in the states
of Andhra pradesh, Assam, Tamil nadu and grows wild in Deccan plateau
and some parts of central India.
Custard apple is considered as one of the delicious and nutritionally
valuable fruit meant for table pupose. Fruits have an edible, soft, granular,
juicy and sugary pulp with mild flavour and with slight acidity. Fruits are
considered for their medicinal value besides their general use in ice cream,
confectionery and certain milk products.
Custard apple ripen within four days after harvest. Fruits can safely
be ripened in straw and fruit leaves and stored at room temperature with a
shelf life of four days. The ripe fruits being soft require careful handling in
marketing. Like many other tropical fruits, the mature custard apple fruits
get chilling injury if stored below 15C, while ripe fruits can be stored at
5C, for six weeks (Jagdish prasad et.al.1995). Considering the fast
increasing area under custard apple cultivation, methods of its preservation
and processing technology needs to be developed to regulate the prices of
produce during glut period.
Custard apple contains about 28-55 % of edible portion consisting of
73.30 % of moisture, 1.60% protein, 0.30% fat, 0.70% mineral matter,
23.90% carbohydrates, 0.20% calcium, 0.04% phosphorous, 1.0% iron,
12.4 to 18.15% sugar, 0.26 to 0.65% acidity with a total calorific value of
105 calories /100 g.
The present study is conducted with the following objectives:
1. Storage of the custard apple pulp and assessment of the quality of stored
pulp.
2. Preparation of value added products like squash, nectar, ready-to-serve
(RTS) beverage and toffee from custard apple pulp.
3. To study the shelf life of products prepared, at room temperature and
cold storage for a period of 4 months.
4. To evaluate the quality of the products at regular intervals.
CHAPTER – II
REVIEW OF LITERATURE
Review of literature pertaining to the present study is presented
under the following sections.
1. Physico-morphological characters and chemical composition of
custard apple.
2. Extraction of pulp.
3. Storage of pulp.
4. Preparation of products.
5. Shelf life of the products.
Physico-morphological characters and chemical composition of
custard apple:
The general composition, adaptability, ripening, storage and
marketing of custard apple were studied. Custard apple is considered
as one of the delicious and nutritionally valuable fruit. Custard apple
contains about 28-55% of edible portion consisting of 73.30%
moisture, 1.60% protein, 0.30% fat, 0.70% mineral matter, 23.90%
carbohydrates, 0.20% calcium, 0.40% phosphorous, 1.0% iron, 12.4-
18.15% sugar, 0.26-0.65% acidity and with a calorific
value of 105 calories / 100 g. Custard apple is generally
classified as semi wild fruit by virtue of its spontaneous spread in
forests, wastelands and other uncultivated places. Custard apple
ripen within four days after harvest. Fruits can safely stored at
room temperature with a shelf life of four days when treated with
calcium carbide and further ripened in straw and fruit leaves
(Jagdish prasad et.al., 1995).
Physico-morphological characters and chemical
composition of custard apple fruits of 7 varieties viz.,
Washington PI-107005, Balanagar, Red sitaphal, Washington PI-
98797, Mammoth, Local sitaphal, British Guinea were studied.
The total soluble solids varied from 20.60-280 brix, total sugars
from 14.9-21.6 percent. Custard apple fruits of all varieties were
poor source of vitamin C, pectin and protein (Beerh et.al., 1983).
Extraction of pulp:
The extraction of pulp from ripe bael fruit by addition of
water equal to pulp (with seeds and fibre), adjusting the pH to 4.3
with citric acid and heating at 80C for 1 minute was described.
The application of heat not only inactivated the enzymes but also
helped in dissolving the mucilage uniformly to provide a
homogenous pulp (Roy et al., 1979).
Kotecha et.al., (1995) and Dhumal et.al., (1996) described
the extraction of pulp from ripened custard apple fruits. The
ripened fruits were washed and cleaned thoroughly and the pulp
was extracted manually by cold hand press extraction method
and was homogenized in an automatic mixer.
Storage of pulp:
Preparation and storage of pulp, squash, nectar and ready-
to-serve beverages from two varieties of apricots grown in
Kumaon region of Uttar pradesh was studied. Storage studies on
apricot pulp have shown that the pulp quality was satisfactory
upto 9 months of storage at room temperature (13 –43 C).
Nectars and squashes were also prepared and adjudged
satisfactory upto 6 months storage (Manan et.al., 1992).
The shelf life of guava pulp stored at 5 C by addition of
potassium metabisulphite, ascorbic acid either alone or
combination with heating at 85 C was studied. After 3 months,
the unspoiled pulp was utilized for the preparation of ready-to-
serve beverage (Rouhangiz Hayati et.al., 1992).
Litchi pulp was preserved and used for squash making. At
low temperature pulp stays fresh for more than a year by addition
of 1g/l of potassium metabisulphite (Vijay sethi et.al., 1983).
Preparation of products:
For the extraction of juice from custard apple pulp 0.2%
pectinase and 4 hrs incubation period were found to be optimum.
The organoleptic evaluation of RTS showed that the beverage
prepared by using 20% juice was most acceptable (Kotecha et.al.,
1995).
Chauhan et.al., (1993) prepared highly acceptable juice
beverages from apricot, peach and plum by blending 20% pulp,
7% sugar, 0.1% salt and 0.1% citric acid.
Guava pulp treated with 0.1% potassium metabisulphite
packed in glass containers or poly vinyl chloride and stored at 5
C for 3 months can be utilized for beverage production which is
comparable with RTS prepared from fresh pulp due to its better
colour, taste and flavour (Rouhangiz Hayati et.al., 1992).
Different products like jam, chutney, squash, drink, toffee
and powder can be prepared from wild apricot for its profitable
utilization (Sharma et.al., 1993).
The process of preparation of bael fruit nectar with 35%
pulp, 25 brix and 0.3% acidity was described. Similarly, 50%
pulp, 50 brix and 1.0% acidity was found suitable for squash. A
good quality toffee was prepared by mixing bael fruit pulp (100
parts), sugar (40 parts), glucose (4.5 parts), skim milk powder
(10 parts) and hydrogenated fat (6parts). Sulphur dioxide (1500
ppm) was added before rolling into sheets (Roy et.al., 1979).
Papaya fruit based toffee can be prepared with added
bengal gram flour along with sugar, vanaspathi, glucose and
orange peel oil (Shastri et.al., 1979).
Custard apple toffees were prepared by using different
levels of sugar and skim milk powder. Good quality custard
apple toffees can be prepared by using 750g sugar, 20g skim
milk powder, 120g vanaspati, 2g citric acid and 5g salt per
kilogram of custard apple pulp (Dhumal et.al., 1996).
Shelf life of the products:
Except for slight reduction in reducing sugars content,
there was no marked changes in the chemical parameters of the
RTS beverages prepared from watermelon juice during 4 months
of storage (Chakraborthy et.al., 1993).
The chemical analysis of the products prepared from
stored guava pulp showed that the total acidity was almost same
as in fresh fruit and the stored pulp. The ascorbic acid of fruit
was lower than extracted pulp due to oxidation of ascorbic acid.
Reducing and total sugars were also higher in fresh fruit than in
the pulp. The pH of fruit was slightly higher than pulp
(Rouhangiz Hayati et.al., 1992).
Reduction in non-reducing sugars and increase in reducing
and total sugars was observed in bael fruit products after 6
months storage. There was practically no change in organoleptic
quality in frozen pulp after 6 months (Roy et.al., 1979).
Jamun juice and nectar could be successfully stored for
one year in cool chamber with a temperature ranging from 9.3-
26.5 C (Khurdiya et.al., 1985).
Ready-to-serve beverage prepared from two varieties of
jack fruits and stored at room temperature to study the storage
stability showed that there was an increasing trend in the acidity
and reducing sugars and decreasing trend in pH, total sugars,
ascorbic acid but, total soluble solids did not change during
storage. Sensory quality attributes were found to be increasingly
acceptable even after storing for 6 months at room temperature
(Krishnaveni et.al., 2001).
Aruna et.al., (1997) studied storage quality of papaya
nectar. The study revealed good keeping quality upto 6 months
and after that deterioration in physico-chemical, sensory and
microbiological qualities was observed.
CHAPTER-III
MATERIALS AND METHODS
The methodology of the study is presented in the
following sections
3.1 Location of the experiment
3.2 Experimental details
3.3 Preparation of the products
3.4 Shelf life study of the products
3.5 Data presentation
3.6 Statistical analysis
The details of the materials used and the methods adopted
during the course of present investigation entitled “studies on
preservation and processing of custard apple pulp” are elucidated
in this chapter.
LOCATION OF THE EXPERIMENT:
The experiment was carried out at Post Harvest
Technology, Department of Horticulture; Post graduate Research
Centre and Department of Agricultural Microbiology and
Bioenergy, college of Agriculture, Rajendranagar, Hyderabad.
Procurement of fruits:
Custard apples (Annona squamosa L.) were used for this
experiment. The fruits were procured in bulk from the local
market.
Chemicals:
Chemicals used in experimentation and analysis were of
analytical grade, purchased from standard Indian companies.
Media and chemicals used for microbial analysis were also from
standard companies.
EXPERIMENTAL DETAILS:
Extraction of pulp:
Fully ripened fruits were selected and the pulp was
extracted manually under hygienic conditions. The seeds and
pulp were separated from each other by rubbing the mixture on a
30-mesh sieve leaving the seeds and the covering sheath of the
carpellary pulp.
Storage of the pulp:
The extracted pulp was added with 1500 ppm of
potassium metabisulphite, packed in individual packs of 1kg and
½kg in polyethylene bags of 150 guage and stored at 5 C for a
period of 6 months from November 2002 to April 2003 till the
pulp is used for preparation of various products.
PREPARATION OF THE PRODUCTS:
After 6 months of storage, the stored pulp was analyzed
both chemically and microbiologically before preparing the
products and utilized for various products preparation.
The various products prepared from custard apple pulp
are:
1. Squash
2. Nectar
3. Ready-to-serve beverage
4. Toffee
Method of preparation:
Squash
Ingredients used
Pulp: 1 Kg
Sugar: 1.8 Kg
Water: 1 l.
Potassium metabisulphite: 0.6 g/l. squash
Citric acid: 5 g
Sugar syrup was prepared to which citric acid was added.
The syrup was cooled and homogenized pulp was added and
mixed thoroughly. Potassium metabisulphite was added as
preservative, filled in bottles and capped. Squash needs to be
diluted before serving.
Flow chart for preparation of squash
Preparation of syrup
(Sugar + water +citric acid, heating just to dissolve)
Straining
Mixing with homogenized pulp
Addition of preservative
Bottling
Capping
Storage
Ready-to-serve beverage
Ingredients used
Pulp: 1 Kg
Sugar: 1.2 Kg
Citric acid: 28g
Water: 7.7 l.
Homogenized pulp was mixed with sugar solution of 13
brix to which citric acid was added and filled in sterilized bottles.
The bottles were filled till it overflows to remove air and foam,
crown corked and pasteurized at 90C for 25 minutes, cooled and
stored. Ready-to-serve beverage should not be diluted before
serving.
Flow chart for preparation of RTS beverage
Fruit pulp
Mixing with strained syrup solution
(Sugar + water + acid, heated just to
dissolve)
Bottling
Crown Corking
Pasteurization at 90 C/25 minutes
Cooling
Storage
Nectar
Ingredients used
Pulp: 1 Kg
Sugar: 0.6 Kg
Citric acid: 13g
Water: 3.3l.
Homogenized pulp was mixed with sugar solution of 15
brix to which citric acid was added .The solution was filled in
sterilized bottles till it overflows to remove air and foam. They
are then crown corked and pasteurized at 90C for 25 minutes,
cooled and stored.
Flow chart for preparation of nectar
Fruit pulp
Mixing with strained syrup solution
(Sugar + water + acid, heated just to dissolve)
Bottling
Crown corking
Pasteurization at 90 C/25 minutes
Cooling
Storage
Toffee
Ingredients used
Fruit pulp: 5.3 Kg.
Sugar: 3 Kg.
Glucose: 0.5 Kg.
Skim milk powder: 0.5 Kg.
Vanaspathi fat: 0.5 Kg.
Pulp was concentrated to 1/3 its original weight by
stirring. Ingredients like sugar, vanaspathi, and glucose were
added and cooked till a drop of the product put in water forms a
compact mass. Skim milk powder dissolved in small amount of
water was then added to the mixture and continued cooking till
the mass leaves the sides of vessel. The final product was
transferred into greased plates and allowed to set. It was then cut
into small pieces, wrapped in butter paper and stored.
Flow chart for preparation of toffee
Homogenized pulp
Concentrating the pulp to 1/3rd its volume by
stirring
Addition of sugar, glucose
Putting fat/ghee in pan
Transfer pulp to pan
Cooking till sufficiently solid
Addition of skim milk powder dissolved in water
Spreading on greased plate
Cooling and cutting into pieces
Wrapping in butter paper
Storage in air tight containers
SHELF LIFE STUDY OF THE PRODUCTS:
The prepared products were stored both at room
temperature and cold storage (5-10C) to study the shelf life of
the products. The products are initially analyzed chemically,
microbiologically and organoleptically before storage.
Observations recorded:
Custard apple attains a bitter taste upon exposure to heat,
but it is interesting to note that there was no such bitterness
observed in any of the products prepared even though all the
products prepared involved heat processing. The products were
analyzed at an interval of every 30 days for the following
parameters and recorded.
Physico-chemical analysis of the products:
pH:
The pH of the products was determined by using a pH
meter.
Total soluble solids ( 0 brix ):
The percentage of total soluble solids were determined by
using “Erma” hand refractometer and expressed as percent total
soluble solids ( 0 brix ) (Ranganna, 1986).
Acidity:
The acidity of the samples was determined by diluting an
aliquot of the sample with distilled water and titrating with 0.1N
NaoH using phenolpthalein as indicator. The calculated acidity
was expressed as percent anhydrous citric acid.
Sugars (%):
Reducing sugars and total sugars were determined by the
method of “Lane and Eynon” (1923).
Reducing sugars:
To 25g of the sample in a volumetric flask 100ml of water
was added and neutralized with 1N NaoH. 2ml of 66% lead
acetate solution was added and kept for 10 minutes. Excess lead
acetate was precipitated by necessary amount of 20% potassium
oxalate, made upto the volume with water, filtered and taken in
burette.
10ml of mixed Fehling’s solution was taken in 250ml
conical flask. Little quantity of the sample was run into flask and
heated to boil moderately for 2 minutes. 3 drops of methylene
blue solution was added and completed the titration until the
indicator was completely decolourized. Brick red colour of the
solution indicates the end point.
Total sugars:
For total sugars 50ml of filtered sample was taken in a
250ml conical flask to which 50ml water and 5g of citric acid
was added, boiled gently for 10 minutes to complete the
inversion of sucrose, transfered to 250ml volumetric flask and
neutralized with 1N NaoH. The volume was made upto the mark
and determined the total sugars as invert sugars.
Ascorbic acid (mg/100ml or 100g sample):
Ascorbic acid was estimated by visual titration method
(Ranganna, 1986).
10ml of the sample was made upto 100ml with 3%
metaphosphoric acid and filtered. To estimate the interference of
sulphur dioxide in the sample, 10ml of the filtrate was taken and
added with 1ml of 40% formaldehyde and 0.1ml 0f Hcl and kept
for 10 minutes. The sample was titrated with the standard 2,6-
dichlorophenol-indophenol dye to a pink end-point that should
persist for atleast 15 seconds.
Sulphur dioxide:
Sulphur dioxide in the sample was calculated by modified
“Ripper titration” method (Ranganna, 1986).
To two similar aliquots of the sample 5ml of 5N NaoH
was added and allowed to stand for 20 minutes. To one of the
samples 7ml of 5N HCl was added and titrated immediately with
0.02N iodine to a definite dark blue colour with 1% starch
solution as indicator (a).
To determine the reducing substances other than sulphite,
the second sample was also acidified with 7ml of 5N Hcl and
10ml of 36-40% formaldehyde was added and kept for 10
minutes. The sample was titrated until a dark blue colour persists
for atleast 15 seconds (b). Volume of iodine used by the total
sulphur dioxide present in the sample is equal to (a-b) ml.
Organoleptic evaluation of the products:
The products developed from custard apple were assessed
every month by a panel of 10 judges. The qualities considered
during the study were appearance, colour, flavour, taste and
overall acceptability.
Selection of panel members:
Panel members were selected from students of food
science and technology, Acharya N.G. Ranga Agricultural
university, Rajendranagar, Hyderabad.
Development of score card:
In order to evaluate the sensory qualities of developed
products, descriptive test, which analytically describes the
sensory qualities of a product, was used. In order to rank the
sensory qualities, ordinal scoring method (ranking) was used
(Peryam and Pilgrim, 1957). Five-point scale was used for
ranking i.e., from 1 to 5 and details of ranks/scores are as
follows.
5 – Excellent
4 – Good
3 – Fair
2 – Poor
1 – Very poor
A score card was developed to evaluate the acceptability
of the products. The analysis was carried out in a room, which
was free from all disturbances in mid afternoon (3pm).
Microbiological evaluation of the products:
Microbiological studies were conducted at 1st and 3rd
month of storage. Total plate count (TPC), yeast and mould
count, coliform and E.coli were undertaken.
The procedure of Cruick Shank et.al, (1975) was used for
total plate count and yeast and mould count. The microbiological
study was carried out at Agricultural Microbiology and
Bioenergy Department, College of Agriculture, Rajendranagar,
Hyderabad.
Total plate count and yeast and mould count by pour-plate
method
Reagents used
Normal saline: 0.8%
Standard plate count agar
Potato dextrose agar
Equipment and Materials used
Petriplates
Test tubes
Pipettes
Spatula
Incubation chamber
Microscope
Procedure
Ten-fold serial dilution of the bacterial suspension was
prepared. Normal saline was used as a diluent for the organism.
9ml of the diluent was pipetted into several sterile test tubes. The
bacterial suspensions were uniformly mixed. Using a sterile 1ml
pipette, 1ml of the suspension was transferred into the first tube
of diluent and mixed thoroughly. From this mixed dilution, 1ml
was transferred to the next diluent. Similar dilutions were made
in the same way using fresh pipettes.
1ml of each dilution (from the greatest dilution) was
pipetted into sterile petri plates and 15ml of molten agar medium
which was cooled around 45 C was poured into plates
containing diluted samples. The agar medium was immediately
distributed by gently mixing the petridish in circular movements
both clock wise and anti clock wise on a flat bench and then
allowed to set evenly and the inverted plates were incubated for
1-2 days and 3-5 days at 37 C for bacterial and yeast and
moulds respectively.
For total plate count, total plate count agar and potato
dextrose agar for yeast and mould count was used.
Coliform and E.coli count:
Media used
Lactose broth
Eiosine- methylene blue (EMB) agar
Equipment and Materials used
Test tubes
Durham’s tubes
Agar medium plates/ Petri plates
Pipettes (10, 1 ml).
Procedure
10ml of the sample was inoculated in double strength
lactose broth in 5 test tubes, 1ml in 5 test tubes single strength
lactose broth and 0.1ml in other set of lactose broth test tubes and
incubated at 35C for 24+/- 2hrs. After incubation they were
observed for gas production. Gas production in Durham’s tubes
indicates positive test. Positive test tubes were separated and
inoculated in Brilliant green lactose bile broth and incubated for
24-48hrs. Presence of gas production indicates positive test.
From the positive tubes, inoculated in EMB agar and streaking
was done. The plates were incubated for 24-48hrs. After the
development of colonies, they were differentiated by observing
colony morphology and Gram’s staining.
DATA PRESENTATION:
All the details pertaining to physico-chemical changes in
the processed products like acidity, reducing and total sugars
were presented per 100g of the product. Thus all the values were
represented as percentage. Sulphur dioxide was represented as
ppm and ascorbic acid as mg/100g of the sample. The sensory
qualities of each parameter were expressed for 5 points since the
highest rank was 5. Microbiological qualities in the products
were presented for 1ml.
STATISTICAL ANALYSIS
In order to understand the significant changes on storage,
analysis of variance (ANOVA) and CRD test was carried out for
sensory parameters like colour, appearance, flavour, taste and
overall acceptability for each product (Panse and Sukhatne,
1985). Similar analysis was done to understand the significant
changes in the physico-chemical characteristics such as pH, total
soluble solids, acidity, ascorbic acid, sulphur dioxide, reducing
and total sugars.
CHAPTER - IV
RESULTS
Various custard apple products were developed at laboratory
level and stability of these products at two different storage conditions
were evaluated. The results were subjected to appropriate statistical
analyses and presented in this chapter.
1. Laboratory studies
1.1 Development of processed custard apple products
Four products were developed with custard apple pulp stored for
6 months at 5C. They include squash, nectar, ready-to-serve beverage
(RTS) and toffee. Physico-chemical characteristics, organoleptic
qualities and microbial safety of processed custard apple products, were
studied.
Procedure for preparation of the products
Squash
Sugar syrup was prepared with 1.8 kg sugar in 1 l of water to
which citric acid was added. The syrup was cooled and 1 kg of
homogenized pulp was added and mixed thoroughly. 0.6 g / l potassium
metabisulphite was added as preservative, filled in bottles and capped.
RTS
1 kg of homogenized pulp was mixed with sugar solution of 13
brix to which 28 g of citric acid was added; filled in sterilized bottles.
The bottles were filled till it overflows to remove air and foam, crown
corked and pasteurized at 90C for 25 minutes, cooled and stored.
Nectar
1 kg of homogenized pulp was mixed with sugar solution of 15
brix to which 13 g of citric acid was added. The solution was filled in
sterilized bottles till it overflows to remove air and foam, crown corked
and pasteurized at 90C for 25 minutes cooled and stored.
Toffee
5.3 kg of custard apple pulp was concentrated to 1/3 its original
weight and ingredients like 3 kg sugar, 0.5 kg vanaspathi, and 0.5 kg
glucose were added and cooked till a drop of product put in water forms
a compact mass. O.5 kg skim milk powder dissolved in small amount of
water was added to the mixture and continued cooking till the mass
leaves the sides of vessel, poured in to greased plates and allowed to set.
It was then cut into small pieces and wrapped in butter paper.
1.2 Physico – chemical characteristics of processed custard apple
products
Initially for all the processed products of custard apple, analysis
was carried out to determine the values for different parameters. The
initial values of the products before storage are presented in the table 1.
The pH was higher for squash (4.26) followed by nectar (3.74)
and RTS (3.34). The total soluble solids were higher in squash (510B).
Acidity was higher for nectar (0.44%) followed by toffee (0.39%).
Ascorbic acid was found to be higher in toffee (9.15 mg /100g) followed
by squash (6.96 mg/100ml). Sulphur dioxide was higher in squash (376
ppm). Reducing sugars and total sugars were higher in toffee [15.16 %
and 68.25%].
Effect of processing on physico – chemical characteristics of custard
apple products.
The pH was found to be lower in all the products when compared
to the stored pulp (5.62) from which the products were prepared. The
total soluble solids (TSS) were higher in squash compared to pulp. The
total acids were lower in all the products than the fruit pulp from which
the products were developed. Ascorbic acid loss was enormous in case
of all the products, except for a slight decrease in toffee. SO2 also
decreased enormously in all the products compared to the stored pulp on
processing. Reducing and total sugars were found to be higher in squash
and toffee compared to pulp on processing.
Organoleptic evaluation of processed custard apple products
A panel of 10 judges assessed the products developed from
custard apple initially. The qualities considered during the study were
appearance, colour, flavour, taste and overall acceptability. A maximum
score of 5 was taken as standard for considering the quality of the
product. All the processed products ranked excellent in all the qualities.
Data pertaining to the initial organoleptic evaluation of the custard apple
products are presented in table 2.
Microbial evaluation of processed custard apple products
The products developed were analyzed initially for microbial
quality. Microbial studies like total plate count (TPC), yeast and mould
count, coliform and E. coli count were carried out to evaluate the safety
and keeping quality of the products. Data pertaining to microbial
evaluation of processed custard apple products before storage are
presented in table 3. Squash contained higher number of TPC [90
CFU/ml] followed by toffee [70 CFU/g]. TPC were absent in nectar and
RTS initially before storage. Yeast and mould count were negligible in
all the products initially. Analysis of the products for coliform count
revealed their presence in pulp and nectar. E.coli were absent in all the
products.
1.3 Storage studies on processed custard apple products
The products developed, were stored at two different storage
conditions (i.e.) at room temperature and cold storage for a period of 4
months and their physico-chemical characteristics were evaluated every
month for different parameters.
pH
Data pertaining to pH are presented in table 4. There were
significant differences in pH among the products and storage periods at
different storage conditions. Squash contained significantly higher pH
(4.01) followed by nectar (3.54) and RTS (3.15). The pH was found to
be higher in products kept at cold storage compared to that at room
temperature. There was significant difference in pH of products among
the storage periods. The pH was least after 4 months of storage. It was
significantly lower than the 1st month of storage. pH during 3rd and 4th
month of storage were on par.
The interaction effects of products and storage conditions,
products and storage periods and storage periods and storage conditions
did not show any significant difference.
Total soluble solids (TSS)
Data pertaining to the total soluble solids are presented in table 5.
There were significant differences in total soluble solids among the
products during different storage periods and different storage
conditions. TSS was found to be significantly higher in squash. Nectar
and RTS contained lower amount. The TSS of nectar and RTS were
almost equal (13.37 and 13.00). The TSS was significantly higher in
products stored at cold storage (26.36) compared to that stored at room
temperature (25.90). There were significant differences in TSS of
products among different storage periods, but the difference was
gradual. There was significant decrease in TSS after 4 months of storage
compared to 1st and 2nd month of storage. There was a slight increase in
TSS during 2nd month of storage, which decreased significantly during
storage. It was on par with 1st month of storage. 3rd and 4th month of
storage period were at par.
The interaction effects of products and storage conditions were
significant. There was increase in TSS in squash but not in nectar or
RTS stored at cold storage. TSS of RTS was found to be same both at
cold storage and room temperature (13.00).
There were significant differences for the interaction effects
between products and storage periods. Squash contained higher TSS
followed by nectar. Second month of storage showed higher TSS, which
was on par with 1st month of storage, which in turn was on par with 3rd
and 4th month of storage.
The interaction effects were not significant between storage
period and storage conditions. Similar pattern was also observed
between products, periods and storage conditions.
Acidity
Data pertaining to acidity are presented in table 6. There were
significant differences in acidity among the products and the products
differed distinctly with each other. Nectar contained higher % of acidity
followed by toffee. Squash contained lower %. Acidity was significantly
higher in products stored at cold storage compared to that at room
temperature. There were significant differences in acidity of the
products at different storage periods. Acidity was least after 4 months of
storage. It was on par with 3 months storage and significantly lower than
1st, 2nd and 3rd months of storage.
The interaction effects of products and conditions were
significant. At room temperature acidity was more in toffee (0.41%)
followed by nectar (0.36%) and RTS (0.34%), which were at par. In
cold storage higher acidity was observed in nectar (0.49%) followed by
toffee (0.39) and RTS (0.33). The products stored at room temperature
showed higher % of acidity except for squash and nectar where acidity
was more at cold storage, but nectar had significantly higher acidity.
The interaction effects of products and storage periods showed
significant difference. In all the products higher % of acidity was
observed during 2nd month of storage compared to 3rd and 4th month.
There was significant decrease in acidity from 2nd month at each
successive month of storage.
The interaction effects of storage conditions and storage periods
showed significant differences. At room temperature and cold storage
acidity was significantly higher at 2nd month (0.63 %) compared to 1st
month (0.29) and further decreased during 3rd and 4th month of storage.
At room temperature squash and nectar showed higher acidity. In RTS
there was significant decrease in acidity and there was no change in
toffee. The interaction between products, storage periods and storage
conditions was also significant.
The interaction effects of products, storage periods and storage
conditions were significant. In squash there was an increase in acidity in
2nd month, decrease in 3rd month and no change in 4th month. In nectar
acidity % increased upto 3rd month in cold storage and during 4th month
there was no change. In RTS, acidity was higher in 1st month under cold
storage but significantly lower in 2nd and 3rd month with no change in 4th
month. There was decrease in acidity of toffee during 1st month with no
change on subsequent storage period.
Ascorbic acid
Data pertaining to ascorbic acid are presented in the table 7. The
results showed significant differences in ascorbic acid among products
and storage periods and the products distinctly differed with each other.
Toffee showed higher amount of ascorbic acid (6.72 mg/100g) followed
by squash (4.08 mg/100ml) and nectar (2.8 mg/100ml). Nectar and RTS
were at par. Storage conditions did not show any significant effect.
Ascorbic acid content was lower during 1st month storage (3.21
mg/100ml) but increased significantly during storage (4.14 mg/10 ml).
Storage periods 2nd, 3rd and 4th months were at par.
The interaction effects of products and storage conditions were
significant. At cold storage, squash and nectar showed higher amount of
ascorbic acid compared to room temperature. RTS showed higher
ascorbic acid content at room temperature. At room temperature nectar
and RTS were at par, with lower ascorbic acid, which differed
significantly with squash and toffee. In cold storage also similar trend
appeared but the products differed significantly among themselves with
the least in RTS (1.56 mg/ 100 ml).
The interaction effects of products and storage periods showed
significant differences. In squash and nectar higher ascorbic acid content
was recorded at 2nd and 4th month of storage compared to 1st month.
There was significant decrease in ascorbic acid in RTS with storage
period from 2nd month (2.2–1.74 mg/100ml). With toffee higher
ascorbic acid was found during 3rd and 4th month of storage.
There were significant differences for the interaction effects
between storage conditions and storage periods. At cold storage there
was significant increase in ascorbic acid by 4th month. At cold storage,
storage period 1st and 3rd months were at par. Similarly 3rd and 2nd
months were at par.
At room temperature the ascorbic acid was lower during 4th
month compared to 1st and 2nd months. The interaction between
products, storage periods and storage conditions were significant.
There was significant increase in ascorbic acid during 1st and 4th
months in squash, nectar and toffee at cold storage. In RTS however
there was significant decrease in ascorbic acid from 2nd month onwards
in cold storage compared to room temperature.
Sulphur dioxide
Data pertaining to sulphur dioxide are presented in table 8. There
were significant differences in sulphur dioxide among the products and
storage periods and different storage conditions. Squash contained
significantly higher ppm of SO2 (234.27 ppm) followed by toffee
(228.98 ppm), which were at par with each other. Nectar and RTS
contained lower amount of SO2 and differed significantly. There were
significant differences in SO2 of products among the storage periods.
The SO2 was least after 4 months of storage. It was on par with 3rd
month of storage and significantly lower than 1st and 2nd month of
storage.
The interaction effects of products and storage conditions were
significant. At room temperature RTS had lower amount followed by
nectar with lower ppm of SO2 which differed significantly from squash
and toffee which had higher ppm of SO2. In cold storage the products
differed significantly among themselves with the least in RTS
(67.2ppm) and highest in squash (320.8 ppm). There was a significantly
higher amount of SO2 in squash, nectar and toffee at cold storage
compared to RTS at room temperature.
There were significant differences for the interaction effects
between products and storage periods. Highest SO2 was found in nectar
and toffee during 1st month followed by 2nd which differed significantly.
Where as in squash higher SO2 content was found in 2nd month which
was significantly higher than that in 4th month. In RTS there was no
difference in SO2 content during 4th month of storage
The interaction between storage period and storage conditions
were significant. During 4th month lower SO2 content was observed at
both the storage conditions compared to 1st and 2nd month.
Interaction between products, storage periods and storage
conditions showed significant result. In general there was significantly
higher SO2 content in squash and toffee under cold storage at all storage
periods compared to that at room temperature. There was no such
difference in RTS and nectar, except for 1st month in nectar under cold
storage. In squash there was significant increase in SO2 content from 1st
to 2nd month of storage without further change under room temperature.
Where as under cold storage there was significant decrease from 1st to
2nd month without significant difference in later periods. In toffee at
room temperature there was significant decrease in SO2 upto 3rd month.
Where as under cold storage there was significant decrease upto 2nd
month. In RTS there was no difference in SO2 content in either storage
conditions or storage periods.
Reducing sugars
Data pertaining to reducing sugars are presented in table 9. There
were significant differences in reducing sugars among the products and
storage conditions and the products distinctly differed with each other.
Squash contained significantly higher % of sugars (34.26 %) followed
by toffee ( 26.09 %). Nectar and RTS contained lower amounts. The
reducing sugar content was significantly higher in products stored at
cold temperature (21.57 %) compared to that at room temperature
(18.36 %). There were significant difference in reducing sugars content
of products among the storage periods. The reducing sugars were least
after 4 months of storage (17.63 %). It was on par with the 3 months
storage and significantly lower than 1st and 2nd months of storage, which
were at par.
The interaction effects of products and storage conditions were
significant. At room temperature nectar and RTS were on par with lower
reducing sugar %, which differed significantly with squash and toffee,
which had higher reducing sugar %. In cold storage also similar trend
appeared but the products differed significantly among themselves with
the least in RTS (7.5%) and highest in squash (40%). There was a
significant increase in reducing sugars % in cold storage compared to
ambient condition in squash and nectar and there were no difference
with RTS and toffee in storage conditions.
There were significant differences for the interaction effects
between products and storage periods. In squash and toffee higher
percent of reducing sugar content was recorded at 2nd and 3rd months of
storage compared to 1st and 4th months. They were on par with each
other, whereas with nectar the reducing sugar content decreased during
2nd and 3rd month and with RTS there was no significant difference with
storage periods.
The interaction effects were not significant between storage
conditions and storage periods. The interaction between products,
storage periods and storage conditions were not significant.
Total sugars
Data pertaining to total sugars are presented in table 10. There
were significant differences in percent of total sugars among products
and storage periods and the products distinctly differed with each other.
Squash contained significantly higher % of sugars (75.4%) followed by
toffee (64.48%). Nectar and RTS contained lower. The total sugars
content was significantly higher in the products stored at room
temperature compared to that stored at cold storage. There were
significant differences in total sugars percent of products among the
storage periods. The total sugar percent was least after 4 months of
storage. It was significantly lower than 2nd and 3rd months of storage.
The interaction effects of products and storage conditions were
significant. At room temperature toffee and squash were at par with
higher sugar percent, which differed significantly with nectar and RTS,
which had lower sugar percent. In cold storage also the products showed
similar trend but the products differed significantly among themselves
with least in RTS (14.53%) and highest in squash (78.6%). There was
significant increase in total sugar percent in squash and nectar stored at
cold storage compared to ambient condition and with decrease in RTS
and toffee.
There were significant differences for the interaction effects
between products and storage periods. In all the products higher total
sugar content was recorded at 2nd month of storage. In squash 2nd and 3rd
months of storage were on par with each other, whereas with nectar 1st
and 3rd months were at par. 2nd and 3rd months of storage in RTS were at
par.
The interaction effects of storage periods and storage conditions
were significant. At room temperature and cold storage total sugars were
higher during 2nd month of storage. Total sugars were higher in squash,
nectar and lower in toffee at cold storage compared to room
temperature.
The interaction between products, periods and conditions were
significant. There was significant increase in total sugar content in
squash stored at room temperature (43.80 % - 58.42 %) and cold
storage. In nectar, RTS and toffee there was a significant decrease in
total sugar content in both the storage conditions with increase in storage
period. In toffee there was significant increase in total sugars during 2nd
and 3rd months of storage with further decrease during 4th month at room
temperature whereas under cold storage there was significant decrease in
total sugars from 1st to 4th months of storage. In nectar stored under cold
storage total sugars was higher during 2nd month of storage which
decreased significantly. There was significant decrease in total sugars in
nectar stored at room temperature with the storage period. Similar trend
was observed in RTS stored at room temperature and cold storage.
Organoleptic evaluation of stored custard apple products
The products developed from custard apple were stored at 2
different storage conditions for 4 months and each month they were
organoleptically assessed by a panel of 10 judges. The qualities
considered during the study were appearance, colour, flavour, taste and
overall acceptability. A maximum score of 5 was taken as standard for
considering the quality of the product.
Appearance
The data pertaining to appearance of the stored products are
presented in table 11. There were significant differences in appearance
among products and storage periods. Highest score for appearance was
seen for RTS stored at cold storage (4.55) followed by RTS at room
temperature (4.45). Least values were observed for toffee stored at room
temperature (4.13). Nectar and toffee stored at room temperature and
RTS were on par which were again on par with all other products except
for toffee at room temperature. Higher value for appearance was
observed during 1st month of storage (4.9) which decreased upon
storage. The products stored at cold storage obtained higher values for
appearance compared to that at room temperature.
Colour
Data for colour of the stored products are presented in table 12.
There were significant differences in colour among different products
and different storage periods. Higher values for colour were obtained for
RTS at cold storage (4.52) followed by Nectar and toffee stored at cold
storage (4.4). Lower values were observed for toffee at room
temperature (3.95). Nectar, RTS and toffee stored at cold storage were
on par. 1st month of storage period showed higher values for colour
which decreased gradually upon storage. All the products stored at cold
storage showed higher values for colour compared to that at ambient
temperature.
Flavour
Data pertained to flavour are presented in table 13. There were
significant differences in flavour among the products and storage
periods at different storage conditions. Higher values for flavour were
obtained for squash stored at cold storage (4.47) followed by RTS at
cold storage (4.37). Nectar stored at room temperature showed lower
values (3.85). Squash stored at cold storage was on par with RTS at cold
storage which was on par with squash and RTS stored at room
temperature. Higher values for flavour were obtained during 1st month
which was on par with 2nd month of storage. All the products stored at
cold storage showed higher values for flavour compared to that at
ambient temperature.
Taste
Data pertaining to taste are presented in table 14. The results
showed significant differences in taste among the products and storage
periods at different storage conditions. Squash stored at cold storage
showed higher value for taste (4.47) followed by RTS stored at cold
storage (4.4). Squash and RTS stored at cold storage and toffee stored at
room temperature were at par. RTS, squash, toffee stored at room
temperature and nectar, RTS, squash and toffee stored at cold storage
were on par. Higher values for taste were obtained during 1st month of
storage which decreased significantly upon storage.
All the products stored at cold storage showed higher values for
taste compared to that at room temperature.
Overall acceptability
Data pertaining to overall acceptability of the products are
presented in table 15. There were significant differences in overall
acceptability among the products, storage periods and different storage
conditions. Higher values for overall acceptability was obtained for RTS
stored at room temperature (4.57) followed by nectar and RTS at cold
storage (4.52). Squash, nectar, RTS and toffee stored at cold storage and
RTS at room temperature were on par. Higher values for overall
acceptability was obtained during 1st month which was on par with 2nd
month of storage. The overall acceptability of the products decreased
with the storage periods.
Microbial analysis
Microbiological studies like total plate count of bacteria, yeast
and mould count, coliform and E. coli count were carried out at 1st and
3rd month for the processed products stored at two different storage
periods to evaluate the safety and keeping quality of the products.
Total plate count (TPC)
Data pertaining to total plate count are presented in table 16.
Total plate count was carried out till 10-3 dilution level. There was a
significant difference in TPC among the products and storage conditions
at different storage periods. Squash contained significantly higher
number of bacteria [365], RTS contained lower number [15]. TPC in
nectar and toffee were on par. The TPC was significantly higher in
products stored at room temperature than at cold storage. There were
significant differences in TPC of products among the storage periods.
The TPC increased with the increase in storage periods in all the
products.
The interaction effects of products and storage conditions were
significant for all the dilutions. At room temperature TPC in nectar and
toffee were on par, which differed significantly with squash with high
number of TPC (510).
In cold storage also similar trend appeared and the products
differed significantly among themselves with least in RTS (5) and
highest in squash (220). At cold storage nectar and toffee were on par.
There was a significant increase in TPC in room temperature
compared to cold storage in all the products.
There were significant differences for the interaction effects
between products and storage periods. In squash, nectar and RTS higher
number of TPC was recorded during 1st month of storage compared to
2nd month whereas, in toffee the TPC decreased during 4th month of
storage compared to 2nd month.
The interaction effects were not significant between storage
conditions and storage periods. At room temperature and cold storage
higher number of TPC was found during 4th month of storage compared
to 2nd month of storage.
The interaction effects between products, storage periods and
storage conditions were not significant.
Yeast and mould count
Data pertaining to yeast and mould count are presented in table
17. Yeast and mould count was carried out till 10-3 dilution. There was a
significant difference in yeast and mould count among the products and
storage conditions at different storage periods. Squash contained
significantly higher number of yeast and moulds [480], RTS contained
lower number [27]. The yeast and mould count was significantly higher
in products stored at room temperature than cold storage. There were
significant differences in yeast and mould count of products among the
storage periods. The yeast and mould count increased with increase in
storage periods.
The interaction effects of products and storage conditions were
significant. At room temperature nectar and RTS were on par. Nectar
and toffee at room temperature were on par. All the products stored at
room temperature differed significantly with squash with high number
of count. In cold storage also similar trend appeared and the products
differed significantly among themselves with least in RTS (10) and
highest in squash (360). There was a significant increase in yeast and
mould count in all the products at room temperature compared to cold
storage.
There were significantly differences for the interaction effects
between products and storage periods. There was significant increase in
the growth of yeast and moulds with the storage period in all the
products.
The interaction effects between storage periods and storage
conditions were significant. Both the products stored at room
temperature and cold storage showed significant increase in yeast and
mould count with increase in storage periods.
The interaction effects between products, storage periods and
storage conditions showed significant difference.
Table – 1 : Physico – chemical characteristics of custard apple pulp and its products before storage.
Parameters Pulp Squash Nectar RTS Toffee
pH 5.62 4.26 3.74 3.34 -
TSS( Brix) 28 51 14 13 -
Acidity % 0.51 0.32 0.44 0.32 0.37
Ascorbic acid (mg/100 ml or 100 g)
9.22 6.96 2.32 2.32 9.15
Sulphurdioxide (ppm)
883.97 376 160 96 320
Reducing sugars (%)
20.75 42.83 20.5 14.16 58.16
Total sugars (%)
21.42 57.53 23.62 17.12 68.25
Table – 2 :Organoleptic characteristics of custard apple products before storage.
Attributes Squash Nectar RTS Toffee
Appearance 5 5 5 4.9
Colour 5 4.9 5 4.7
Flavour 5 5 4.6 4.8
Taste 5 4.9 4.6 4.8
Overall acceptability
5 5 4.9 4.7
Table – 3 : Microbiological characteristics of custard apple pulp and its products before storage.
Products Total plate count (CFU/ml or g sample)
Yeast and mould count(CFU/ml or g
sample)
Pulp 20 20
Squash 90 30
Nectar 10 10
RTS NIL NIL
Toffee 70 20
STORAGE STUDIES ON PROCESSED CUSTARD APPLE PRODUCTS Table 4 : pH of processed custard apple products.
Storage conditions
C1 3.54
C2 3.60
S.E 0.01
CD (P = 0.05) 0.04
Products
P1 4.01
P2 3.54
P3 3.15
S.E 0.01
CD (P = 0.05) 0.05
Storage periods
Pe1 3.75
Pe2 3.59
Pe3 3.49
Pe4 3.44
S.E 0.02
CD (P = 0.05) 0.06
Products x storage periods
Products – storage periods
P1 P2 P3
Pe1 4.22 3.70 3.33
Pe2 4.05 3.58 3.16
Pe3 3.92 3.46 3.11
Pe4 3.85 3.45 3.03
S.E 0.03
CD (P = 0.05) NS
pH of stored custard apple products Storage conditions x Storage periods
Storage conditions
Storage periods
C1 C2
Pe1 3.74 3.76
Pe2 3.54 3.64
Pe3 3.45 3.54
Pe4 3.42 3.46
S.E 0.03
CD (P = 0.05) NS
Products x storage conditions
Storage conditions products
C1 C2
P1 3.97 4.04
P2 3.51 3.58
P3 3.13 3.18
S.E 0.02
CD (P = 0.05) NS
Table 5: Total soluble solids of custard apple products (Brix)
Storage Conditions
C1 25.90
C2 26.36
S.E 0.03
CD (P = 0.05) 0.11
Products
P1 52.02
P2 13.37
P3 13.00
S.E 0.04
CD (P = 0.05) 0.13
Storage periods
Pe1 26.16
Pe2 26.27
Pe3 26.08
Pe4 26.00
S.E 0.05
CD (P = 0.05) 0.15
Products x Storage conditions
Products / Storage conditions C1 C2
P1 51.37 52.66
P2 13.33 13.41
P3 13.00 13.00
S.E 0.06
CD (P = 0.05) 0.19
Products x Storage periods
Products
Storage periods
P1 P2 P3
Pe1 51.50 14.00 13.00
Pe2 51.66 14.16 13.00
Pe3 52.00 13.25 13.00
Pe4 52.91 12.08 13.00
S.E 0.09
CD (P = 0.05) 0.27
Storage conditions x Storage periods
Storage periods / Storage conditions C1 C2
Pe1 26.00 26.33
Pe2 26.11 26.44
Pe3 25.83 26.33
Pe4 25.66 26.33
S.E 0.07
CD (P = 0.05) NS
Table 6 : Acidity of custard apple products (%)
Storage Conditions
C1 0.33
C2 0.37
S.E 0.002
CD (P = 0.05) 0.0083
Products
P1 0.25
P2 0.42
P3 0.34
P4 0.40
S.E 0.004
CD (P = 0.05) 0.0117
Storage periods
Pe1 0.33
Pe2 0.67
Pe3 0.24
Pe4 0.17
S.E 0.004
CD (P = 0.05) 0.0117
Products x Storage conditions
Products / Storage conditions C1 C2
P1 0.23 0.28
P2 0.36 0.49
P3 0.34 0.33
P4 0.41 0.39
S.E 0.006
CD (P = 0.05) 0.016
Products x Storage periods
Products
Storage periods
P1 P2 P3 P4
Pe1 0.28 0.25 0.41 0.38
Pe2 0.47 0.92 0.67 0.64
Pe3 0.15 0.35 0.15 0.32
Pe4 0.12 0.19 0.12 0.26
S.E 0.008
CD (P = 0.05) 0.023
Storage conditions x Storage periods
Storage periods / Storage conditions C1 C2
Pe1 0.29 0.37
Pe2 0.63 0.71
Pe3 0.25 0.23
Pe4 0.17 0.17
S.E 0.006
CD (P = 0.05) 0.016
Table 7 : Ascorbic acid of custard apple products (mg/100ml or 100g sample)
Storage Conditions
C1 3.92
C2 3.91
S.E 0.0462
CD (P = 0.05) NS
Products
P1 4.08
P2 2.80
P3 2.07
P4 6.72
S.E 0.0654
CD (P = 0.05) 0.1845
Storage periods
Pe1 3.21
Pe2 4.20
Pe3 4.12
Pe4 4.14
S.E 0.0654
CD (P = 0.05) 0.1845
Products x Storage conditions
Products / Storage conditions C1 C2
P1 3.87 4.30
P2 2.45 3.15
P3 2.58 1.56
P4 6.79 6.65
S.E 0.09
CD (P = 0.05) 0.26
Products x Storage periods
Products
Storage periods
P1 P2 P3 P4
Pe1 3.00 2.22 2.20 5.45
Pe2 4.64 3.19 2.32 6.65
Pe3 4.06 2.90 2.03 7.50
Pe4 4.64 2.90 1.74 7.28
S.E 0.013
CD (P = 0.05) 0.37
Storage conditions x Storage periods
Storage periods / Storage conditions C1 C2
Pe1 2.49 3.94
Pe2 4.92 3.48
Pe3 4.48 3.76
Pe4 3.79 4.48
S.E 0.09
CD (P = 0.05) 0.26
Table 8 : Sulphur dioxide of custard apple products (ppm)
Storage Conditions
C1 124.06
C2 189.58
S.E 2.5301
CD (P = 0.05) 7.1412
Products
P1 234.27
P2 99.20
P3 64.85
P4 228.98
S.E 3.5781
CD (P = 0.05) 10.0992
Storage periods
Pe1 178.22
Pe2 163.22
Pe3 147.67
Pe4 138.18
S.E 3.5781
CD (P = 0.05) 10.0992
Products x Storage conditions
Products / Storage conditions C1 C2
P1 147.75 320.80
P2 88.80 109.60
P3 62.50 67.20
P4 197.22 260.73
S.E 5.06
CD (P = 0.05) 14.28
Products x Storage periods
Products
Storage periods
P1 P2 P3 P4
Pe1 241.00 124.80 76.80 270.30
Pe2 244.80 104.00 64.00 240.10
Pe3 227.30 96.00 59.40 208.00
Pe4 224.00 72.00 59.20 197.52
S.E 7.15
CD (P = 0.05) 20.19
Storage Conditions x Storage periods
Storage periods / Storage conditions
C1 C2
Pe1 134.90 221.55
Pe2 136.00 190.45
Pe3 116.95 178.40
Pe4 108.42 167.93
S.E 5.06
CD (P = 0.05) 18.97
Table 9 : Reducing sugars of custard apple products (%)
Storage Conditions
C1 18.36
C2 21.57
S.E 0.5569
CD (P = 0.05) 1.5719
Products
P1 34.26
P2 11.37
P3 8.15
P4 26.09
S.E 0.7876
CD (P = 0.05) 2.2230
Storage periods
Pe1 20.83
Pe2 21.91
Pe3 19.50
Pe4 17.63
S.E 0.7876
CD (P = 0.05) 2.2230
Products x Storage conditions
Products / Storage conditions C1 C2
P1 28.46 40.05
P2 9.58 13.15
P3 8.81 7.50
P4 26.59 25.60
S.E 1.11
CD (P = 0.05) 3.14
Products x Storage periods
Products
Storage periods
P1 P2 P3 P4
Pe1 30.99 16.89 10.86 24.58
Pe2 40.51 8.14 7.73 31.26
Pe3 35.31 7.82 6.77 28.12
Pe4 30.22 12.64 7.26 20.43
S.E 1.57
CD (P = 0.05) 4.44
Storage conditions x Storage periods
Storage periods / Storage conditions C1 C2
Pe1 19.79 21.86
Pe2 20.34 23.47
Pe3 18.21 20.79
Pe4 15.09 20.18
S.E 1.11
CD (P = 0.05) NS
ORGANOLEPTIC EVALUATION OF STORED CUSTARD
APPLE PRODUCTS Table 11 : Appearance of custard apple products
Products
P1 4.22
P2 4.25
P3 4.30
P4 4.37
P5 4.45
P6 4.55
P7 4.12
P8 4.42
S.E 0.1184
CD (P = 0.05) 0.2321
Storage periods
Pe1 4.90
Pe2 4.65
Pe3 3.78
Pe4 4.01
S.E 0.0837
CD (P = 0.05) 0.1641
Storage periods x products
Products Storage periods
P1 P2 P3 P4 P5 P6 P7 P8
Pe1 5.00 5.00 4.90 5.00 4.90 5.00 4.70 4.70
Pe2 4.40 4.50 4.40 4.70 5.00 4.90 4.60 4.70
Pe3 3.60 3.80 4.10 3.90 3.90 3.70 3.40 3.90
Pe4 3.90 3.70 3.80 3.90 4.00 4.60 3.80 4.40
S.E 0.2369
CD
(P=0.05)
0.6102
P1 = Squash at room temperature
P2 = Squash at cold storage
P3= Nectar at room temperature
P4 = Nectar at cold storage
P5 = RTS at room temperature
P6 = RTS at cold storage
P7 = Toffee at room temperature
P8 = Toffee at cold storage
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Table 12 : Colour of custard apple products
Products
P1 4.20
P2 4.27
P3 4.30
P4 4.40
P5 4.32
P6 4.52
P7 3.95
P8 4.40
S.E 0.1235
CD (P = 0.05) 0.2421
Storage periods
Pe1 4.8
Pe2 4.61
Pe3 3.78
Pe4 3.98
S.E 0.0874
CD (P = 0.05) 0.1712
Storage periods x products
Products Storage periods
P1 P2 P3 P4 P5 P6 P7 P8
Pe1 5.00 5.00 4.90 4.80 4.90 5.00 4.30 4.50
Pe2 4.90 4.80 4.50 4.70 4.50 4.60 4.30 4.60
Pe3 3.30 3.60 3.90 4.00 3.80 4.10 3.50 4.10
Pe4 3.60 3.70 3.90 3.90 4.10 4.40 3.70 4.40
S.E 0.2471
CD
(P=0.05)
0.6364
P1 = Squash at room temperature
P2 = Squash at cold storage
P3= Nectar at room temperature
P4 = Nectar at cold storage
P5 = RTS at room temperature
P6 = RTS at cold storage
P7 = Toffee at room temperature
P8 = Toffee at cold storage
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Table 13 : Flavour of custard apple products
Products
P1 4.32
P2 4.47
P3 3.85
P4 4.12
P5 4.30
P6 4.37
P7 4.02
P8 4.20
S.E 0.1234
CD (P = 0.05) 0.2418
Storage periods
Pe1 4.66
Pe2 4.60
Pe3 3.66
Pe4 3.91
S.E 0.0873
CD (P = 0.05) 0.1710
Storage periods x products
Products Storage periods
P1 P2 P3 P4 P5 P6 P7 P8
Pe1 5.00 4.90 4.60 4.60 4.50 4.40 4.60 4.70
Pe2 5.00 5.00 4.40 4.40 5.00 4.70 4.20 4.10
Pe3 3.50 3.90 3.20 3.70 3.60 3.90 3.70 3.80
Pe4 3.80 4.00 3.20 3.80 4.10 4.50 3.60 4.20
S.E 0.2468
CD
(P=0.05)
0.4837
P1 = Squash at room temperature
P2 = Squash at cold storage
P3= Nectar at room temperature
P4 = Nectar at cold storage
P5 = RTS at room temperature
P6 = RTS at cold storage
P7 = Toffee at room temperature
P8 = Toffee at cold storage
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Table 14 : Taste of custard apple products
Products
P1 4.30
P2 4.47
P3 4.10
P4 4.32
P5 4.25
P6 4.40
P7 4.00
P8 4.35
S.E 0.1235
CD (P = 0.05) 0.2420
Storage periods
Pe1 4.63
Pe2 4.50
Pe3 3.81
Pe4 4.15
S.E 0.0873
CD (P = 0.05) 0.1711
Storage periods x products
Products Storage periods
P1 P2 P3 P4 P5 P6 P7 P8
Pe1 4.90 5.00 4.40 4.70 4.70 4.60 4.10 4.70
Pe2 4.80 4.80 4.30 4.60 4.30 4.50 4.30 4.40
Pe3 3.60 3.90 3.60 3.90 3.70 3.90 3.80 4.10
Pe4 3.90 4.20 4.10 4.10 4.30 4.60 3.80 4.20
S.E 0.2469
CD
(P=0.05)
NS
P1 = Squash at room temperature
P2 = Squash at cold storage
P3= Nectar at room temperature
P4 = Nectar at cold storage
P5 = RTS at room temperature
P6 = RTS at cold storage
P7 = Toffee at room temperature
P8 = Toffee at cold storage
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Table 15 : Overall acceptability of custard apple products
Products
P1 4.30
P2 4.47
P3 4.35
P4 4.52
P5 4.57
P6 4.52
P7 4.20
P8 4.47
S.E 0.1074
CD (P = 0.05) 0.2106
Storage periods
Pe1 4.88
Pe2 4.75
Pe3 3.88
Pe4 4.18
S.E 0.0760
CD (P = 0.05) 0.1489
Storage periods x products
Products Storage periods
P1 P2 P3 P4 P5 P6 P7 P8
Pe1 5.00 5.00 4.90 4.80 5.00 4.90 4.70 4.80
Pe2 4.90 4.90 4.70 4.80 4.90 4.70 4.50 4.60
Pe3 3.50 3.90 4.10 4.10 4.00 3.80 3.60 4.10
Pe4 3.80 4.10 3.70 4.40 4.40 4.70 4.00 4.40
S.E 0.2149
CD
(P=0.05)
0.4212
P1 = Squash at room temperature
P2 = Squash at cold storage
P3= Nectar at room temperature
P4 = Nectar at cold storage
P5 = RTS at room temperature
P6 = RTS at cold storage
P7 = Toffee at room temperature
P8 = Toffee at cold storage
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 4.20 3.98 3.98 3.83 4.24 4.12 3.95 3.88
P2 3.70 3.54 3.40 3.42 3.70 3.62 3.52 3.49
P3 3.32 3.12 3.07 3.03 3.34 3.20 3.15 3.03
S.E 0.05
CD
(P=0.05)
NS
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 51.00 51.16 51.33 52.00 52.00 52.16 52.66 53.83
P2 14.00 14.16 13.16 12.00 14.00 14.16 13.33 12.16
P3 13.00 13.00 13.00 13.00 13.00 13.00 13.00 13.00
S.E 0.13
CD
(P=0.05)
NS
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 0.24 0.38 0.19 0.12 0.32 0.57 0.12 0.12
P2 0.12 0.83 0.32 0.19 0.38 1.02 0.38 0.19
P3 0.38 0.70 0.19 0.12 0.44 0.64 0.12 0.12
P4 0.42 0.64 0.32 0.26 0.35 0.64 0.32 0.26
S.E 0.0118
CD
(P=0.05)
0.0332
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 1.56 5.80 4.64 3.48 4.44 3.48 3.48 5.80
P2 1.11 3.48 2.90 2.32 3.33 2.90 2.90 3.48
P3 2.20 2.90 2.90 2.32 2.20 1.74 1.16 1.16
P4 5.11 7.5 7.50 7.07 5.80 5.80 7.50 7.50
S.E 0.1849
CD
(P=0.05)
0.5218
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 110.81 160.00 160.20 160.00 371.20 329.60 294.40 288.00
P2 102.40 96.00 89.60 67.20 147.20 112.00 102.40 76.80
P3 70.40 64.00 58.00 57.60 83.20 64.00 60.80 60.80
P4 256.00 224.00 160.00 148.90 284.60 256.20 256.20 246.15
S.E 10.1205
CD
(P=0.05)
28.5649
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 23.98 33.52 30.44 25.90 38.00 47.50 40.18 34.54
P2 17.50 7.52 7.05 6.28 16.28 8.76 8.59 19.00
P3 12.60 7.86 6.52 8.26 9.12 7.60 7.03 6.26
P4 25.11 32.47 28.86 19.94 24.06 30.05 27.38 20.92
S.E 2.22
CD
(P=0.05)
NS
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
MICROBIOLOGICAL EVALUATION OF STORED CUSTARD APPLE PRODUCTS
Table 16 : Total plate count of custard apple products
Storage conditions CFU/ml or g sample
C1 160
C2 73
S.E 0.2932
CD (P = 0.05) 0.8446
Products
P1 365
P2 45
P3 15
P4 40
S.E 0.446
CD (P=0.05) 1.1944
Storage periods
Pe1 86
Pe2 146
S.E 0.2932
CD (P=0.05) 0.8446
Products x storage conditions
P1 C1 510
P1 C2 220
P2 C1 50
P2 C2 40
P3 C1 25
P3 C2 5
P4 C1 50
P4 C2 30
S.E 0.5863
CD (P=0.05) 1.6892
P1 Pe1 270
P1 Pe2 460
P2 Pe1 20
P2 Pe2 70
P3 Pe1 5
P3 Pe2 25
P4 Pe1 50
P4 Pe2 30
S.E 0.5863
CD (P=0.05) 1.6892
C1 Pe1 127
C1 Pe2 190
C2 Pe1 45
C2 Pe2 102
S.E 0.4146
CD (P=0.05) NS
* CD (P – 0.01)
Table 17 : Yeast and Mould count of custard apple products
Storage conditions CFU/ml or g sample
C1 200
C2 122
S.E 0.3187
CD (P = 0.05) 0.9182
Products
P1 480
P2 57
P3 27
P4 80
S.E 0.4507
CD (P=0.05) 1.2985
Storage periods
Pe1 72
Pe2 250
S.E 0.3187
CD (P=0.05) 0.9182
P1 C1 600
P1 C2 360
P2 C1 45
P2 C2 70
P3 C1 45
P3 C2 10
P4 C1 110
P4 C2 50
S.E 0.6374
CD (P=0.05) 1.8363
P1 Pe1 250
P1 Pe2 710
P2 Pe1 25
P2 Pe2 90
P3 Pe1 5
P3 Pe2 50
P4 Pe1 10
P4 Pe2 150
S.E 0.6374
CD (P=0.05) 1.8363
Storage conditions x storage periods
C1 Pe1 85
C1 Pe2 315
C2 Pe1 60
C2 Pe2 185
S.E 0.4507
CD (P=0.05) 1.2985
Table 10 : Total sugars of custard apple products (%)
Storage conditions
C1 43.33
C2 42.39
S.E 0.2408
CD (P = 0.05) 0.6797
Products
P1 53.79
P2 16.95
P3 14.61
P4 64.48
S.E 0.3406
CD (P = 0.05) 0.9613
Storage periods
Pe1 30.84
Pe2 50.22
Pe3 46.99
Pe4 43.39
S.E 0.3406
CD (P = 0.05)
Products x Storage conditions
Storage conditions
products
C1 C2
P1 52.21 58.60
P2 13.00 20.90
P3 14.70 14.53
P4 73.42 14.53
S.E 0.48
CD (P = 0.05) 1.35
Products x Storage periods
Products
Storage periods
P1 P2 P3 P4
Pe1 52,71 16,74 14.27 52.65
Pe2 55.48 19.24 16.65 76.53
Pe3 52.32 16.88 16.11 69.76
Pe4 54.75 14.96 11.43 58.98
S.E 0.68
CD (P = 0.05) 1.92
Storage conditions x Storage periods
Storage conditions
Storage periods
C1 C2
Pe1 32.46 29.22
Pe2 50.11 50.34
Pe3 47.77 46.21
Pe4 42.99 43.80
S.E 0.48
CD (P = 0.05) 1.35
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 C2
Pe1 Pe2 Pe3 Pe4 Pe1 Pe2 Pe3 Pe4
P1 43.80 55.07 55.56 58.42 35.62 41.90 41.90 45.00
P2 17.20 13.70 11.55 9.57 16.28 24.78 22.22 20.35
P3 15.11 15.11 15.00 12.12 13.44 17.14 16.82 10.75
P4 53.75 55.50 55.60 53.85 57.56 54.57 53.93 49.11
S.E 0.96
CD
(P=0.05)
2.71
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 2nd month of storage
Pe3 = 3rd month of storage
Pe4 = 4th month of storage
Storage conditions x Products x Storage periods
C1 (CFU/ml or g sample) C2 (CFU/ml or g sample)
Pe1 Pe2 Pe3 Pe4
P1 420 600 120 320
P2 20 80 20 60
P3 10 40 0 10
P4 60 40 40 20
S.E O.8292
CD(P=0.05) NS
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 3rd month of storage
Storage conditions x Products x Storage periods
C1 (CFU/ml or g sample) C2 (CFU/ml or g sample)
Pe1 Pe2 Pe3 Pe4
P1 300 900 200 520
P2 10 80 40 100
P3 10 80 0 20
P4 20 200 0 100
S.E O.9014
CD(P=0.05) 2.5969
NS = Non significant
C1 = Room temperature
C2 = Cold storage
P1 = Squash
P2 = Nectar
P3 = RTS
P4 = Toffee
Pe1 = 1st month of storage
Pe2 = 3rd month of storage
CHAPTER – V
DISCUSSION
Custard apple products like squash, nectar, RTS and toffee were
prepared from preserved custard apple pulp and stored at room
temperature and cold storage for a period of 4 months to study the
stability of the products. The products were analysed every month for
physico-chemical and organoleptic qualities. The microbioligical safety
of these products were also analysed.
The results obtained for custard apple pulp and processed custard
apple products are discussed in this chapter under the following
headings.
5.1 Physico-chemical characteristics of custard apple pulp and its
products
5.2 Storage studies of processed custard apple products
5.3 Organoleptic evaluation of custard apple products
5.4 Microbiological evaluation of custard apple products
5.5 Overall review
5.1 Physico-chemical characteristics of custard apple pulp and its
products
pH
The pH of all the products prepared from the stored pulp was
lower compared to the pulp. The pH of the stored pulp was 5.62. The
initial pH of the products prepared were squash 4.26, nectar 3.74 and
RTS 3.34. The decrease in pH of the products may be attributed to the
added citric acid. Decrease in pH of nectar due to added citric acid was
reported by Teotia et al. (1997) and Aruna et al. (1997) in case of
papaya.
Total soluble solids (TSS)
The TSS of the stored pulp was 28. Initial TSS reading of the
squash was found to be higher (51), which is due to added sugars in
squash that increased the TSS value. The lower TSS value in nectar
(14) and RTS (13) is due to the dilution of the products. However,
TSS of the products were in accordance with the FPO specifications.
Acidity
Acidity was found to be lower in all the products prepared
compared to the stored pulp. This may be due to the dilution of the
products during processing. The acidity of the pulp preserved was
0.51%. The acidity of the products were squash 0.32%, nectar 0.44%,
RTS 0.32% and toffee 0.37%.
Ascorbic acid
Ascorbic acid content was found to be lower in all the products
prepared compared to the stored pulp. The reduction in ascorbic acid
may be attributed to its destruction by oxidation or heat during
processing. Similar observations were reported by Teotia et al. (1997)
for muskmelon.
Sulphurdioxide
Custard apple pulp was stored by the addition of 1500 ppm of
potassium metabisulphite. The SO2 content of the pulp after a storage
period of 6 months was found to be 884 ppm which was within the FPO
specifications. SO2 content of the products prepared from the stored pulp
were lower compared to the pulp and varied depending upon the
product. The decrease in the SO2 content may be attributed to the
dilution of the product with water or due to varying levels of pulp used
during preparation of the products or due to its destruction by heat. The
initial SO2 content of squash was 376 ppm and nectar 160 ppm which
were higher than the FPO specifications which allows 350 ppm and 100
ppm of SO2 in squash and nectar respectively. SO2 content of RTS was
within the specified limit (96 ppm). Reduction in SO2 content in pulp
upon storage was reported by Teotia et al. (1997) for muskmelon.
Hence, it can be expected that the marginally higher levels of SO2 in
squash and nectar will be reduced to conform to the FPO specifications.
Total sugars and Reducing sugars
The total sugar content of the stored pulp was 21.42%. The total
sugar content of the products prepared were higher than that of the
stored pulp except for RTS. The high sugar content is due to the added
sugar. Though sugar was added in RTS, total sugars was low due to
dilution with water. The initial reducing sugar content of the pulp was
20.75% which increased in all the products prepared except for RTS. A
similar trend was reported by Ranote et al. (1993) for mango pulp.
5.2 Storage studies of processed custard apple products
The products squash, nectar, RTS and toffee prepared from the
stored pulp were stored both at cold storage and room temperature for a
period of 4 months to determine their keeping quality and acceptability.
The products were analysed every month for physico-chemical and
bimonthly for microbiological characteristics to evaluate their stability.
pH
Slight decline in pH of all the products was observed during 4
months of storage. Decrease in pH of the products is due to the added
citric acid during processing. The results obtained are in agreement with
that of Aruna et al. (1997) for papaya products and Chahal et al. (1999)
for water melon juice.
Total soluble solids (TSS)
The TSS of the products stored for 4 months showed varying
results. There was a slight increase in TSS in squash from 51 to 52.9
after 4 months of storage. TSS of squash stored at cold storage was
higher than that at room temperature. Kirpal Singh and Mathur (1953)
observed an increase in TSS in cashew apples under cold storage. Slight
increase of TSS in case of lemon juices after a storage period of 7
months was reported by Palaniswamy et al. (1974).
The TSS of nectar decreased from (14 to 12) upon storage.
Decrease in TSS is may be due to settling down of some soluble
colloidal solids, incipient fermentation and other chemical reactions of
sugar in presence of acid during storage. Decrease in TSS of Kiwi fruit
squashes were observed by Thakur et al. (1998).
There was no appreciable change in TSS of RTS upon storage.
This is in agreement with the results of Jain et al. (1986) for phalsa,
kaphal and litchi squashes and Teotia et al. (1997) for muskmelon RTS.
Acidity
In squash and nectar the acidity was found to be decreasing with
increase in storage periods inspite of a slight decline in pH, the reason
for which is unknown. However, in RTS and toffees the acidity was
higher after 4 months of storage. Increase in acidity in toffees may be
attributed to loss of moisture from the surface of toffees during storage.
These results were similar to that obtained by Kaushal et al. (2001) for
apple pomace toffees. Increase in acidity with decline in pH was
observed in RTS upon storage. Similar results were also reported by
Palaniswamy et al. (1974) for lemon juices and Chahal et al. (1999) for
watermelon juices.
Ascorbic acid
Ascorbic acid showed a continuous decrease in all the products as
the storage period advanced except for a slight increase in nectar. The
loss varied between 6.96 to 4.08 mg/100 ml juice in squash, 2.32 to
12.07 mg/100 ml juice in RTS and from 9.15 to 6.72 mg/100 g sample
in toffee. Similar changes were reported by Palaniswamy et al. (1974)
for lemon juices and squashes, Teotia et al. (1997) for muskmelon RTS
and Aruna et al. (1997) for papaya products.
Loss of ascorbic acid was found to be more in products stored at
room temperature compared to that at cold storage. The results obtained
are in agreement with that of Sahni et al. (1989) for mango nectar.
Similar results were observed by Chahal et al. (1998) for water
melon juice and Tiwari et al. (2001) for Guava RTS. Decreasing levels
of ascorbic acid may be due to its gradual oxidation upon storage.
Sulphur dioxide
There was a gradual decrease in SO2 content of all the products
upon storage. The loss varied between 376 ppm to 234 ppm in squash,
160 to 99 ppm in nectar, 96 to 65 ppm in RTS and 320 to 229 ppm in
toffee. Loss of SO2 was more in products stored at room temperature
compared to that at cold storage. The SO2 content of all the products
stored at room temperature and cold storage were below the FAO
standards except for a slight higher SO2 content in nectar stored at cold
storage (109 ppm). Similar results were put forth by Roy et al. (1979)
for bael fruit products and Kalra et al. (1984) for guava nectar.
Reducing sugars
A decrease in reducing sugar content was observed in squash and
toffee upon storage against increasing reducing sugars upon storage as
reported by Palaniswamy et al. (1974) for lemon juices and squashes,
Teotia et al. (1997) for muskmelon RTS and Kaushal et al. (2001) for
apple pomace toffees.
A decrease in reducing sugar content of papaya toffee and nectar
was reported by Aruna et al. (1997). Decrease in reducing sugars is
because inversion might not have occured in the products.
Total sugars
Slight decrease in total sugars were observed in all the products
with increase in storage period. Similar results were observed by Thakur
et al. (1998) for Kiwi squash and Chahal et al. (1999) for watermelon
juice. The low total sugar content could be due to dilution of the
product. The results of Teotia et al. (1997) for muskmelon RTS and
Tiwari et al. (2001) for guava beverage showed that total sugars were
unchanged upon storage. The total sugar content of the products stored
at room temperature were higher compared to that at cold storage.
5.3 Organoleptic evaluation of custard apple products
All the processed custard apple products were initially evaluated
organoleptically by a panel of 10 judges for their appearance, colour,
flavour, taste and overall acceptability. A maximum score of 5 was
taken as standard for considering the quality of the products. All the
products ranked excellent in all the quality characteristics.
There was a considerable decrease in sensory mean score for
taste, colour, flavour and overall acceptability during storage. The
sensory mean score for each attribute was highest on the day of
preparation which decreased with passage of time. Similar opinion was
put forth by Palaniswamy et al. (1974) for lemon squashes. Decrease in
flavour upon storage may be due to loss of volatile aromatic substances
responsible for flavour. A similar opinion was put forward by Thakur et
al. (1998) in case of kiwi squash. Decrease in colour of the products
may be due to browning reactions in the products. This is in accordance
with the result of Thakur et al. (1998) for kiwi squash. The overall
acceptability of the products decreased as the storage period increased.
Organoleptic evaluation of the processed products remained more
acceptable for products stored at low temperature compared to that at
room temperature. The products stored at room temperature were
acceptable till third month of storage. However, the products stored at
cold storage showed an overall acceptability upto four months of
storage. Retention of colour, taste, flavour and appearance were better in
all the products stored at low temperature indicating that low
temperature storage conditions are better in improving the shelf life
stability of the products. These results are similar with the earlier
observations of Jain et al. (1986) for phalsa, kaphal and litchi squashes,
Chauhan et al. (1993) for fruit juice beverages from pulp and Vijay
Sethi (1995) for mango pulp. However, the products stored at ambient
temperature were also acceptable during the 4 month storage period.
5.4 Microbiological evaluation of custard apple products
Microbial analysis of the stored pulp after a storage period of 6 months
showed very less or negligible total bacterial count and yeast and mould
count. Preservation of pulp at lower temperature of 5C retarded the
growth of bacteria. A similar opinion was expresssed by Rouhangiz
Hayati et al. (1992) for RTS beverages from preserved guava pulp.
However, initial microbial analysis of squash and Toffee revealed
either higher microbial count than the pulp which were also negligible
which might be due to improper handling. Increase in microbial growth
with the storage period was observed in all the products but the increase
was more in the products stored at room temperature compared to that
stored at cold storage indicating the effectiveness of low temperature
storage on the retardation of microbial growth. However, the increase in
microbial growth were within the permissible level. Application of heat
during processing irrespective of holding time reduced the microbial
load. A similar opinion was given by Das et al. (1992) in case of apple
juice, Ghorai (1996) for Kinnow mandarin juice and Supriya Langthasa
et al. (2001) for apple pulp. As the microbial growth was within control
even in the products stored at room temperature, the products can well
be stored at ambient temperature.
Overall review
Pulp was extracted from custard apples during the glut season
and stored for a period of 6 months by addition of 1500 ppm of KMS
and after 6 months various products were prepared and assessed for their
keeping quality at both room temperature and cold storage.
It may be possible for the industries to prepare custard apple pulp
for a few months during the peak season and subsequently utilize it for
products preparation. With that assumption, custard apple pulp was
stored for approximately 6 months before using it for product
preparation. The products were further stored for 4 months to determine
their keeping quality and acceptability.
Physico-chemical, microbial and organoleptic evaluation of the
stored pulp and the products prepared from the stored pulp during
different storage periods indicated that the products could be stored for
at least 4 months without deterioration. Cold storage or low temperature
storage of the products is preferred but in areas where low temperature
facility is not available the product should be stored in dark avoiding
direct exposure to heat and sunlight which may lead to undesirable
changes in the product.
The custard apple products are novel and could be far cheaper.
They could easily find market as custard apple is a seasonal fruit. Cost
of production could not be compared directly as no such products
prepared from custard apple are available in the market at present.
Compared to the products processed from other fruits custard apple
products are far cheaper and the lower cost of production is attributable
to the low cost of basic raw material.
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