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corresponding author: S. Sangheetha, eMail: ssangheetha06@gmail.com
91
IJMS 2014 vol. 1 (1): 91-103
International Journal of Multidisciplinary
Studies (IJMS)
Volume I, Issue I, 2014
Optimization of Palmyrah (Borrasus
flabellifer) Fruit Pulp in Different Varieties
of Fruit Yoghurts
S. Sangheetha1, M. A. J. Wansapala2, A. Gnanasharmala1, S. Srivijeindran1
1Palmyrah Research Institute, Kandy Road, Kaithady, Sri Lanka
2 Department of Food Science and Technology, Faculty of Applied Sciences,
University of Sri Jayewardenepura, Nugegoda, Sri Lanka
ABSTRACT
The research focused on processing palmyrah fruit pulp into a value added product to broaden the utilization
of palmyrah fruit pulp. Set, swiss style, jelly and pulp preserve yoghurts incorporated with palmyrah fruit
pulp were developed. Control yoghurt and plain yoghurt for other preparations were prepared with 13 %
sugar, 1% gelatin, 12 % skim milk powder and lactic acid bacteria culture following household method. The
fresh pulp was kept at – 25 oC for 48 hours and heated up to 85 oC for 30 minutes with 5 % cane sugar, 0.6
% tartaric acid, 1 % ascorbic acid and 0.13 % sodium chloride. The treated pulp was added at 5 %, 7.5 %,
10 %, 12.5 % and 15 % into both set and swiss style yoghurts. Fruit jelly was prepared with sugar, gelatin,
sodium citrate, citric acid and 20 % pulp. It was then incorporated into yoghurt at 5 % and 6 %. Palmyrah
fruit pulp preserve was prepared by heating sugar, pectin and pulp (45. 8 %) until its brix reached 68.5 o
and it was topped on set yoghurt at 5 %, 7.5 % and 10 %. Sensory evaluation for colour, odour, appearance,
mouth feel and texture was conducted with 21 untrained panelists using 5 point hedonic scale and the
optimized pulp concentrations for set, swiss style, jelly and preserve yoghurt were 5 %, 7.5 %, 6 % and 10 %
respectively (p < 0.05). The overall sensory qualities of all palmyrah fruit yoghurts were rated as good to
very good. There were no significant changes in sensory attributes, brix and pH in storage at 4 oC. Shelf life
was 18 days for all products at 4 oC without any preservatives except set yoghurt as it showed separation of
water from the third day of the preparation. Nutritional and microbiological qualities of the products were
investigated and compared with control yoghurt. Protein was higher in swiss style (6.12 %) and jelly (7.77
%) yoghurts. Carbohydrate was higher in swiss style yoghurt (36.87 %) and preserve yoghurt contained
highest fat content (2.57 %).
Keywords: Carbohydrate, fruit yoghurt, palmyrah fruit, pulp, protein
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
92
1. INTRODUCTION
Palmyrah (Borrasus flabellifer) possess a great
capacity to yield several products of economic
importance and hence it is called “Wishing
tree” which means a palm that yields anything
and everything. Almost every part of the palm
is utilized but most of the products from the
palm are made by traditional methods known
from the time immemorial.
It is estimated from the statistical data
of existing female palms in Sri Lanka that,
about 20,000 tons of palmyrah fruit pulp is
available annually during fruit season but
around 10000 tons of pulp is thrown in to
nature or used for animal feeding (Jansz et al
2002) every year because its uses are limited
mainly due to the presence of a bitter
compound and lack of trials are done to process
into various consumer attractive value added
products.
Moreover, palmyrah fruit pulp is
nutritious and has a yellow colour due to
carotenoids which are precursors of vitamin A
and therefore it has potential of being as a
source of vitamin A and giving attractive
yellow colour to foods. In addition to that, it is
revealed that pulp is rich in vitamin C (ascorbic
acid) and a good source of pectin which could
be used to process the fruits into various
products (Theivendrarajah, 2008)
With regard to palmyrah plantation, it
is reported that currently 24.260 hectares
equivalent with 11 million palms are available
of which 3.5 million trees are in Jaffna, 3.5
million in Kilinochchi, 3 million in Mannar and
balance scattered all over the country (Palmyrah
development board 2010). Government's
Mahinda Chintana 10 - year plan aims to
increase the current level of palms from 11
million to 16 million by 2016 and the vision of
it for the future strongly emphasizes on the
need to promote palmyrah based products
including its fruits. Also the government has
given high priority for dairy development
(Ministry of livestock and rural community
development, 2010). Currently major part of
milk production is done by farmers
domestically and their life is as same as that of
palmyrah dependents.
The above facts generated the idea to
produce a value added consumer attractive
product using palmyrah fruit pulp and milk. As
a result the research was conducted with the
aims of developing formulae for different kinds
of palmyrah fruit yoghurts, analyzing nutrient
contents of the yoghurts and determining shelf
lives of them. The research, when industrialized
will give the benefits to the palmyrah
dependents of approximately 1/3rd of the
population of Northern and Eastern provinces
where palmyrah occurs extensively by
increasing the marketing and utilization of
palmyrah fruit pulp, minimizing the wastage of
a nutritive resource and under exploitation of
the health aspects of pulp and employment
opportunities to produce novel product for
consumers.
2. BACKGROUND
Yoghurt is a healthy and delicious fermented
milk product due to its nutritive and therapeutic
value with a custard-like consistency which
differentiates it from other fermented milk
products (Perdigon et al 2002). The Codex
Alimentarious Commission (2008) defines it as
a coagulated milk product obtained by lactic
acid fermentation through the action of
Lactobacillus bulgaricus and Streptococcus
Optimization of Palmyrah Fruit Pulp in Different Fruit Yoghurts
93
thermophilus from milk with or without
additions and the microorganisms in the final
product must be viable and abundant.
Yoghurt is commonly considered as
safer product and nutritionists are being
considering incorporating inexpensive source of
nutrient to make it an almost complete food
(Boghra and Mathur 2002). Yoghurt is easily
digestible and palatable than milk as it contains
less lactose. Further, it is treasured for
controlling the growth of bacteria and in curing
of intestinal disease, for instance, constipation
and diarrhea, lowering of blood cholesterol and
anti-carcinogenic effect (Kamruzzaman et al
2002). Yoghurt is a great source of B vitamins,
phosphorus and calcium. Organoleptic
properties such as flavour, texture and aroma of
yoghurt depend upon so many factors including
the raw materials, manufacturing process and
the bacterial strains used (Kumar and Mishra
2004).
According to the Sri Lankan Standard
for yoghurts (SLS 824 Part 2:1989) a standard
yoghurt should be smooth, glossy surface, no
crack or holes on the top, no whey synersis, no
off flavor or odor and clean layer on the surface
of the yoghurt. It also says that yoghurt must
contain minimum of 3.0 % fat whilst it
categorizes the yoghurt that contains between
0.5 % and 3.0 % fat as low fat yoghurt and that
with less than 0.5 % fat is non-fat yoghurt.
Palmyrah fruit pulp has bitter taste due
to flabelliferins and it gives a negative impact
on utilization of pulp. Despite that from the
point of health, palmyrah fruit pulp has
numerous benefits to us. It is now proved that
flabelliferins lowers the glucose absorption into
blood, increase the cardiac anti oxidant activity
and decrease the blood cholesterol. Recent
studies show that pulp is rich in provitamin A
(32 ppm), vitamin C (285 ppm) (Jeyaratnam
1986) and contains lycopene as well
(Pathberiya and Chandrika 2003). Lycopene is
an anti oxidant which is beneficial in
cardiovascular ailments and cancer.
3. MATERIALS AND METHODOLOGY
3.1 Materials
Fresh milk was procured from Yarlco, the only
dairy production unit in Jaffna peninsula and
cream separation was done there using their
cream separator. Other ingredients were
collected from Jaffna market. Palmyrah fruits
were collected from Kopay and Navatkuli.
Reagents used for chemical and
microbiological analysis of the developed
products were purchased from Sigma Aldrich.
All glassware were obtained from ISO certified
companies in United Kingdom and Germany
and the equipment used for the studies were
caliberated and made in United Stated of
America and Germany.
3.2 Quality tests and preparation of raw
materials
Selection and quality of raw materials are the
major determinants of the quality of end
products in a processing. Therefore raw
materials are analyzed prior to be subjected to
the processing to ensure the production of good
quality end product. In the study, raw milk was
subjected to clot boiling test with 68 % alcohol
according to COMESA/East African Standards.
Also the pH, titrable acidity as lactic acid, total
soluble solid, fat and solid non fat of milk were
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
94
determined. It was boiled up to 80 oC for 15
minutes.
Pest attack free, fresh, black skinned,
well ripe fruits were selected to the study. The
nutlets were dipped in warm water (45 - 50 oC)
for few seconds and then macerated. The ratio
of pulp: added water was 1:0.5 (v/v). Pulp was
then strained through a muslin cloth. It was kept
in deep freezer at -25 oC for about 48 hours.
Palmyrah fruit pulp was treated with 5
% sugar, 0.6 % tartaric acid, 1 % ascorbic acid,
0.2 % citric acid, 0.13 % sodium chloride and 1
% gelatin and the mixture was heated up to 85
oC for 30 minutes to incorparate into set and
swiss style palmyrah fruit pulp yoghurts.
For jelly yoghurt, palmyrah fruit pulp
jelly was prepared with sugar (84 %), gelatin
(11.5 %), tartaric acid (1.06 %), sodium citrate
(0.18 %), water and 20 % pulp following the
house hold method. Sugar (53 %) and pectin
(0.35 %) were heated together with the pulp
(45. 8 %) were heated until brix reached 68.5 o
to prepare fruit preserve for fruit preserve
yoghurt. The preserve was prepared freshy in
each preparation, so that it can eaisly be poured
on the yogurt easily before it gets set.
3.3 Preparation of yoghurts
For the plain yoghurt for all four products, 13
% sugar, 1 % gelatin and 12 % skim milk
powder were added and the amounts of them
were same in all products. The house hold
method for yogurt production was used to
prepare yoghurt using lacitic acid bacteira
culture procured from Jamma. The preparation
of yoghurt, its processing conditions and
ingredients were kept same in the preparation of
all products.
Optimization of pulp in set and swiss style
yoghurts Five recipes in each category of
yoghurts were developed for palmyrah fruit
pulp incorporated set fruit yoghurt and swiss
style yoghurt (Table 1).
TABLE 1: Optimization of fruit pulp
concentrations in palmyrah fruit pulp set
yoghurt and swiss style yoghurt
Treatments
1
2
3
4
5
Treated
fruit pulp
amounts
(g 100 ml-1)
5.00
7.50
10.00
12.50
15.00
Optimization of pulp as jelly in fruit jelly
yoghurt Two recipes of palmyrah fruit pulp
jelly yogurts were prepared by blending the
jelly in different percentages (Table 2). All
ingredients except jelly were kept constant in
all blends.
TABLE 2: Optimization of palmyrah fruit pulp
jelly in swiss style yoghurt
Treatment
Pulp in the jelly added to the
product (g 100 ml-1)
1
5.0
2
6.0
Optimization of pulp as preserve in fruit
preserve yoghurt
Three recipes of palmyrah fruit pulp preserve
incorporated set yoghurts were prepared. Table
3 shows the percentage of palmyrah fruit pulp
preserve added in each treatment. The preserve
was poured on the set yogurt. All ingredients
Optimization of Palmyrah Fruit Pulp in Different Fruit Yoghurts
95
except fruit pulp preserve were kept constant in
all blends.
TABLE 3: Optimization of palmyrah fruit
preserve in palmyrah fruit preserve yoghurt
Treatment
Pulp in the product
(g 100ml-1)
1
5.0
2
7.5
3
10.0
Selection of the formula of each variety of
prepared yoghurts
The formula in each variety of yoghurts which
gained most consumer preference was selected
via sensory evaluation conducted by 21
untrained panelists using 5 point hedonic scale
method and analysis of variance was conducted
on the sample means for flavor, colour, mouth
feel, appearance, texture and over all
acceptability. Statistically significant attributes
were further analyzed to see where mean
difference existed using Minitab (Friedman
test) at 95 % confidence interval (P < 0.05).
3.3 Analysis of selected yoghurts
All selected products were subjected to the
following tests and the results were then
compared with that of control yoghurt.
Chemical analysis
pH, total soluble solids, and titrable acidity
were analyzed according to SLS 824: Part 2,
1989. Crude protein, moisture, crude fat, crude
fibre, ash and total carbohydrate were
determined in accordance with Association of
Analytical Chemists Standard (2002). Same
was done for commercially available plain
yoghurt as control and compared with
developed palmyrah fruit yoghurts.
Microbiological analysis
Total plate count and yeast and mold were
tested for skim milk powder, sugar, milk, water
and milk solution prior to the addition of
culture. E. coli, yeast and mold in the selected
products were assessed according to SLS 824
Part 2: 1989. Same was done for commercially
available plain yoghurt.
Shelf life study
For the shelf life evaluation pH, brix and
titrable acidity were measured once in in three
days for 21 days. At the same time, texture,
appearance, colour, smell and air bubble
formation on the surface of the product were
observed by experienced persons at the station
where the research was carried out.
Experimental design and statistical analysis
Friedman non parametric statistical method was
used to analyze the results of sensory evaluation
data at 95 % confidence level was considered.
4. RESULTS EVALUATION AND DATA
ANALYSIS
4.1 Quality tests and preparation of raw
materials
The analysis showed that the raw milk met the
quality requirements specified in SLS 824: Part
2: 1989 for yogurt preparation. In Table 4 the
fat, solid non fat, density, pH and acidity of the
purcehased milk are given in ranges because the
milk was procured three times throughout the
studies and the tests for fat, solid non fat and
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
96
density of raw milk were carried out for each
batch.
TABLE 4: Quality parameters (fat, solid non
fat, density, pH and acidity) of raw milk used
for the study
Constituent of
raw milk
Range
Fat
0.02 – 0.03 g 100g-1
Solid non fat
7.5 – 7.6 g 100 g-1
Density
28.6 – 29.1
pH
6.6 – 6.7
acidity
0.14 – 0.17 g 100g-1
Clot boiling test is carried out to ensure
the quality of milk. In the test poor quality milk
will coagulate and fine particles of curd will be
visible whereas the quality milk will not give
so. When the acidity of milk exceeds 0.21% the
milk get spoiled and is not good for the
production. The raw milk used in the study did
not clot in the alcohol test and the pH and
acidity were ranged 6.6 - 6.7 and 0.14 – 0.17 %
respectively which fell into the acceptable
ranges of pH and acidity for consumption.
Fruit pulp preparation
It would be better if some parameters such as
penetration ability, pH and total soluble solids
are standardized for the selection of good
quality fruits as it will be more beneficial and
easy to the industries to select super grade fruits
for the production. Palmyrah fruit pulp was
collected and kept in at -25 oC till used in order
to preserve and minimize the bitterness of pulp.
Therefore the pH, brix and acidity were
determined soon after the extraction only. The
pH, total soluble solids and the acidity by
means of ascorbic acid were 4.06, 15.2 % and
0.66 %. Acidity was expressed in terms of
ascorbic acid as this is the dominant acid in the
fruit. The results showed that the pulp was not
spoiled.
Pulp has bitter principle which hinders
its exploitation in food industries. However
Jansz (2006) stated that the bitterness can be
reduced by freezing beyond -20 oC. Therefore
pulp was kept in deep freezer at -25 oC for
about 48 hours to minimize its bitter taste and
the bitterness of fresh pulp and frozen pulp was
compared. It was experienced via tasting that
the frozen pulp was less bitter than the fresh.
After the preparation of pulp for set and
swiss style yoghurts, its texture, aroma and
sweetness were improved and the colour
remained as that of fresh pulp. Tartaric acid was
added to reduce the pH closer to that of
yoghurt. Citric acid and ascorbic acid were
added as anti oxidants to prevent discolouration
in the preparation. Sodium chloride was added
as taste enhancer.
Palmyrah fruit pulp jelly prepared for
the development of fruit jelly yoghurt was
smooth and soft without any bubbles or foam
on the top. The final pH of solution was 3.1
which is the most suitable pH for jelly to settlle
off.
Palmyrah fFruit preserve was darker
than the natural colour of the pulp but the
texture was as same as that of jam. No air
bubbles or sugar crystals formed and it was
smooth and transparency.
Optimization of Palmyrah Fruit Pulp in Different Fruit Yoghurts
97
4.2 Sensory evaluation of yoghurts
Friedman test in Minitab was used to
analyze the results of sensory evaluation to
select the most preferred blend of each type of
palmyrah fruit yoghurt.
Palmyrah fruit pulp set yoghurt
The preference of each sensory attributes of all
palmyrah set yoghurts developed in the study
were rated from 5 to 1. Point 5 was given for
like very much whilst point 1 was dislike very
much.
TABLE 5: Sensory evaluation of set
palmhyrah fruit yoghurt
Sensory
attribut
e
Median score for the products
175
101
115
142
107
Flavour
4a(45.5)
4a(44.0)
3b
(31.5)
3b
(29.0)
3b
(30.0)
Color
4a
(47.5)
4a
(49.0)
3b(33.5)
3b(25.5)
3b
(24.5)
Appeara
nce
4a
(47.0)
4a
(52.5)
3b(29.0)
3b(26.5)
3b
(25.0)
Mouth
feel
4a
(50.0)
4a(49.0)
3b(27.5)
3b(26.5)
3b
(25.0)
Texture
4a
(52.5)
4a
(47.5)
3b(31.0)
3b(26.0)
3b
(23.0)
Same alphabets on means in a row
show non-significant differences at the
confidence level of 95%. Sum of ranks are
given along with the medians in the brackets.
175 - Set yoghurt with 5% fruit pulp
101 - Set yoghurt with 7.5% fruit pulp
115 - Set yoghurt with 10% fruit pulp
142 - Set yoghurt with 12.5% fruit pulp
107 - Set yoghurt with 15% fruit pulp
Results (Table 5) shows that the
products 175 and 101 scored same median 4 for
all analyzed sensory attributes and no
significant difference existed in-between the
products for each attributes. Products 115, 142
and 107 showed significant different between
the other two and among them, and scored less
than 175 and 101. To select the best product
between 175 and 101 the sum of rank had to be
considered as the medians were same for each
attribute. Product 175 has scored higher than
the other for flavor, mouth feel and texture
whereas the product 101 scored higher for
colour and appearance. It would be rather good
if the overall acceptability of the product was
also analyzed. However as 175 scored higher
for flavor, mouth feel and texture which indeed
play in the success of product product 175
which contained 5% fruit pulp was selected as
best.
Palmyrah fruit pulp swiss style yoghurt
Colour, flavour, appearance, mouthfeel and
texture of each blend was rated from 5 to 1
where 5 was assigned to like very much and 1
was to dislike very much.
TABLE 6: Sensory evaluation of palmyrah
fruit swiss style yoghurt
Sensory
attributes
Median score for the products
215
265
253
242
227
Flavour
4a
(35.0)
4a
(35.0)
4a
(35.0)
4a
(33.5)
4a
(37.5)
Color
4a
(33.5)
4a
(39.0)
4a
(38.0)
4a
(32.0)
4a
(37.5)
Appearanc
e
3.85ab
(38.0)
4.15a
(46.0)
3.85bc
(33.5)
3.65c
(26.0)
3.75abc
(36.0)
Mouth feel
3.9a
(39.0)
4a
(39.5)
3.9a
(35.0)
3.9a
(36.5)
3a
(30.0)
Texture
4ab
(34.5)
4.3a
(44.8)
4ab
(36.5)
3b
(31.0)
3.9ab
(34.9)
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
98
Same alphabets on means in a row show
non-significant differences at the confidence
level of 95%. Sum of ranks are given along
with the medians in the brackets.
215 - Swiss style yoghurt with 5% fruit pulp
265 - Swiss style yoghurt with 7.5% fruit pulp
253 - Swiss style yoghurt with 10% fruit pulp
242 - Swiss style yoghurt with 12.5% fruit
pulp
227 - Swiss style yoghurt with 15% fruit pulp
The results of sensory evaluation (Table
6) revealed that the all products have scored the
same median 4 for flavor, colour and mouth
feel and no significant difference existed among
them for each of those attributes. Product 265
scored the highest median and sum rank for
appearance, mouth feel and texture. Also it was
clear that product 265 scored the best for all
sensory attributes. Therefore product 265
containing 7.5% fruit pulp was selected.
From the above results of both types of
yoghurts, it could be noted that the selected
swiss style yoghurt contained higher percent of
pulp (7.5%) than set yoghurt (5%). Also the
comments given by the panelists brought out
that the consistency and appearance of swiss
style yoghurt were better than that of set
yoghurt and bitterness could not be sensed in
swiss style yoghurt although the pulp was
higher in that. About two or three days after the
production set yoghurt showed water
separation and the appearance became down.
Therefore among the selected set and swiss
style yoghurts, swiss style yoghurt with 7.5 %
fruit pulp was selected for further studies.
Palmyrah fruit pulp jelly yoghurt
Sensory evaluation revealed that both products
scored 4.5 median to flavor, colour and texture
and product 307 scored less than product 321
for appearance and mouth feel. Also the sum of
ranks of product 321 were higher than those of
307 for all attributes. Therefore product 321
was selected finally (Table 7).
TABLE 7: Sensory evaluation of palmyrah
fruit jelly yoghurt
Sensory
attributes
Median score for the products
321(5 % of pulp)
307 (6 % of pulp)
Flavour
4.5a (20.0)
4.5a (19.0)
Color
4.5a (21.0)
4.5a (18.0)
Appearance
4.5a (21.5)
3.5b (16.5)
Mouth feel
4.5a (23.5)
3.5b (15.5)
Texture
4.5a (20.0)
4.5a (19.0)
Means in the each row followed by the same
letters are not significantly different at p < 0.05.
Sum of ranks are given along with the medians
in the brackets.
Palmyrah fruit pulp preserve yoghurt
The results of sensory evaluation brought out
that product with 10 % of fruit pulp scored 4.5
median to flavor, colour and texture and mouth
feel and the sum of ranks of product was higher
than the other products with 5 % and 7.5 % fruit
pulp and thus it (product with 10 % of fruit
pulp) was selected.
4.3 Analysis of selected products
Chemical analysis - pH, Brix and acidity pH,
acidity and total soluble solids of the all types
of yoghurts selected in the sensory evaluation
Optimization of Palmyrah Fruit Pulp in Different Fruit Yoghurts
99
were analyzed to determine the chemical
quality of them (Table 8).
TABLE 8: Analysis of pH, acidity and total
soluble solids of palmyrah fruit yoghurts
selected in sensory evaluation
Yoghurt
pH
Total
soluble
solids
Acidity
(g 100g-1)
Palmyrah fruit set yoghurt
4.43
16.9
0.8 ± 0.01
Palmyrah fruit swiss style
yoghurt
4.36
18.6
0.9 ± 0.03
Palmyrah fruit jelly
yoghurt
4.60
21.3
0.97 ± 0.01
Palmyrah fruit preserve
yoghurt
4.33
23.6
1.01 ± 0.01
Control yoghurt
4.27
16.2
0.79 ± 0.02
SLS 824 Part 2: 1989 says that the
acidity by means of lactic acid of a standard
yoghurt should be between 0.8 % and 1.25 %.
Acidity of all products selected in the studiy
was in between the limits specified in the
standard. In contrast, the pH of the products
were slightly higher than the optimum pH of
4.2 for coagulation. It may be due to the acidity
of fruit pulp and the organic acids (citric acid,
tartaric acid etc) added in preparation of pulp
for the product developments.
pH and brix of yoghurts with storage
The results show that the pH and brix did not
change much and they were in acceptable limits
even after 18 days. Fruit jelly yoghurt showed
the pH above 4.2. The change in pH and total
soluble solids of each type of yoghurt were
observed for 21 days (Figures 1, 2, 3 and 4).
Values are means of triplicates.
Vertical bars indicate the standard errors.
FIGURE 1: Study on change of pH and brix of
palmyrah fruit pulp swiss style yoghurt for 21
days
Values are means of triplicates.
Vertical bars indicate the standard errors.
FIGURE 2: Study on change of pH and brix of
palmyrah fruit jelly yoghurt for 21 days
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1st
3
2nd
3
3rd
3
4th
3
5th
3
6th
3
7th
3
pH and Brix
Time interval
pH
Brix
Linear (pH)
Linear (Brix)
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
100
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1st 3
2nd 3
3rd 3
4th 3
5th 3
6th 3
7th 3
pH and brix
Time interval
pH
Brix
Linear
(pH)
Linear
(Brix)
Values are means of triplicates.
Vertical bars indicate the standard errors.
FIGURE 3: Study on change of pH and brix of
palmyrah fruit preserve yoghurt for 21 days
Values are means of triplicates.
Vertical bars indicate the standard errors.
FIGURE 4: Study on change of pH and brix of
palmyrah fruit set yoghurt for 21 days
Although the characterisitcs of
palmyrah fruit pulp set yoghurt were in the
limits, separation of whey and water was
observed on the third day from the development
and the texture was too watery in set yoghurt.
Therefore, the product was then discarded from
further analysis.
The milk solids content (including the
fat content) for yoghurt ranges from around 9 %
for low fat yoghurt to more than 20 % for
certain types of concentrated yoghurt. Many
commercial yoghurt products have milk solids
contents of 14 - 15 % (Tamime and Robinson,
1999). The total solids content of milk can be
increased by concentration processes, such as,
evaporation under vacuum, and membrane
processing (i.e., reverse osmosis and ultra
filtration).
Nutrient analysis of selected palmyrh fruit
yoghurts in the study
Codex Alimentarious Regulations for yoghurt
(2008) indicates that the minimum milk protein
content is 2.7 % (except for concentrated
yoghurt where the minimum protein content is
5.6 % after concentration) and the maximum fat
content is 15 %. The results (Table 9) show that
the fat content of all products did not exceed 15
% and were between 0.71 % and 2.47 %.
Therefore, all palmyrah fruit pulp yoghurts can
be categorized as low fat fruit yoghurts. The
protein content of preserve yoghurt was lower
than the limit as the preserve added for yoghurt
was about 40 % and thus the milk in the
yoghurt was reduced drastically and the
preserve contained almost 60 % of sugar. It
would be more informative about the nutrient
value and medicinal benefits of the products if
the analysis of crude fibre, dietary fibre and
vitamin A is carried out.
Optimization of Palmyrah Fruit Pulp in Different Fruit Yoghurts
101
TABLE 9: Nutrient contents of developed
palmyrah fruit pulp yoghurts
Nutrient
Amount of nutrients (g 100g-1)
Swiss
style
yoghurt
Jelly
yoghurt
Preserv
e fruit
yoghurt
Commerci
al yoghurt
as control
Protein
6.12±
0.05
7.77±0.0
6
2.48±0.0
3
5.26±0.01
Crude fat
0.71±
0.01
0.90±0.0
5
2.47±0.0
3
0.80±0.05
Moisture
55.59±
0.3
66.48±0.
02
61.38±0.
02
65.00±0.15
Ash
0.56
±0.03
0.53±0.0
1
0.92±0.0
2
0.81±0.01
Acid
insoluble
ash
0.15±0.
02
0.46±0.0
0.29±
0.01
0.29±0.01
Carbohydra
te + fibre
36.87±
0.37
23.86±0.
09
32.46±0.
08
27.84±0.12
Palmyrah fruit pulp contains
provitamin A (32 ppm), vitamin C (285 ppm)
and lycopene as well (Mohanajayelauxmy
1986). Apart from the nutritional benefits of
pulp, it was discovered that Flabelliferin II was
preventing the absorption of glucose into the
blood stream with no adverse reactions (Janz
2006). Further it has anti glycemic activities,
anti microbial activities and hypocholestremic
acivities which are benefits for our health. 10 –
12 % pectin in pulp decrease cholesterol by 25
– 35 % by binding bile salts and cholesterol
(Jansz 2006).
Microbiological analysis. According to SLS
824 Part 2: 1989 E.coli, yeast and mold, lactic
acid bacteria, and Salmonella should be
analyzed howbeit since the media was not
available at the time when the research was
carried Salmonella will be checked in future
works of the research. Total plate count test was
done for skim milk powder, sugar, milk and
potable water according to SLS 516 part 1,
1991. But bacterial growth was in acceptable
range in potable water and bacterial growth was
not observed in other ingredients. E. coli was
absent in all products including control yoghurt.
Yeast count of all products were not more than
1000 per gram and Mold did not exist in the
selected products. Mostly the microbial
contamination occurs during the process.
Therefore implementation of hygienic practices
during process will help reduce microbial
contamination.
Organoleptic analysis. Texture, flavor and
appearance were observed one in three days to
determine the shelf life. They remained as fresh
throughout the period of 21 days. But since the
pH and acidity went beyond accepted level after
18 days observations were not taken as it will
not contribute to determine shelf life further.
Shelf life study
pH and brix were measured once in three days
to determine the shelf life of products for 21
days. At the same time, appearance, colour,
smell and texture were observed by experienced
persons. As discussed above in pH and brix
change, the shelf life period was determined as
18 days without any preservatives at 4 oC.
5. CONCLUSION AND FURTHER WORK
The optimized palmyrah fruit pulp
concentrations for its set yoghurt, swiss style
yoghurt, jelly yoghurt and preserve yoghurt
were 5 %, 7.5 %, 6 % and 10 % (v/v)
respectively. All four products complied with
Sri Lankan Standard 824:1989 and the pH, brix
and acidity of the final products were in
S. Sangheetha, M. A. J. Wansapala, A. Gnanasharmala, S. Srivijeindran
102
acceptable ranges. The shelf life of the product
was 18 days at 4oC without any preservatives.
However a complete analysis of nutrients
including vitamin A and C, phyto nutrients and
dietary and crude fibres can give a complete
nutrient profile and nutritional value of the
developed products. Therefore, in the next
season of fruits these constituents will be
analysed. Also, the study on development of
yoghurt with chemically preserved pulp will be
studied. Consumer preference test and
marketing survey should be done to improve its
quality.
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