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Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp

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Yoghurt was produced and flavoured with graded levels of African bush mango juice (ABMJ) and pulp (ABMP). African bush mango (Irvingia gabonensis) juice and pulp was used to substitute 0, 10, 20, 30, 40 and 50% of yoghurt. The chemical, sensory and microbiological properties of the yoghurts were determined using standard procedures. The results showed that the pH of the yoghurt ranged from 4.77 to 5.01. Plain yoghurt (PY) served as the control. The protein, ash, fat and fibre contents decreased with increase in African bush mango juice and pulp while the moisture content increased with increase in African bush mango juice. Micro-nutrient (vitamin A and C) increased with increased level of African bush mango juice and pulp in the yoghurt while (phosphorus and calcium) decreased with increased level of African bush mango juice and pulp in the yoghurt. The reducing sugar increased with increased level African bush mango juice and pulp content of the formulated yoghurt. The total viable count and lactic acid bacteria ranged from 1.2×10 5 to 2.7×10 5 cfu/ml and 7.5×10 4 to 1.2×10 5 cfu/ml respectively. High mean values (7.95) were obtained for the plain yoghurt (control) for all sensory attributes (colour, flavour, taste, aftertaste, consistency and mouth feel) therefore making the sample (PY) most preferred sample with an overall acceptability of 7.95. Sample (PY+ ABMP) 90:10 had the highest mean for general acceptability (6.70) compared to the other flavoured yoghurt samples and was second in overall preference. Samples containing 10, 20, 30% of African bush mango juice in yoghurt were generally acceptable while samples containing 40 and 60% of the juice were generally unacceptable. Samples containing 10 and 20% of African bush mango pulp in yoghurt were generally acceptable while samples containing 30, 40 and 50% of the juice were generally unacceptable. There was no significant (p<0.05) difference between the plain yoghurt and the flavoured yoghurt sample containing 10% African bush mango juice while the difference with the flavoured yoghurt containing 10% African bush mango pulp was significant(p<0.05).
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Food Science and Technology 5(2): 56-69, 2017 http://www.hrpub.org
DOI: 10.13189/fst.2017.050203
Production and Quality Evaluation of Flavoured Yoghurt
from Graded Levels of Sweet Variety of African Bush
Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
Mbaeyi-Nwaoha I. E.*, Umeh L. C., Igbokwe C. J., Obodoechi C. M., Okoronkwo N. C.
Department of Food Science and Technology, University of Nigeria, Nigeria
Copyright©2017 by authors, all rights reserved. Authors agree that this article remains permanently open access under the
terms of the Creative Commons Attribution License 4.0 International License
Abstract Yoghurt was produced and flavoured with
graded levels of African bush mango juice (ABMJ) and pulp
(ABMP). African bush mango (Irvingia gabonensis) juice
and pulp was used to substitute 0, 10, 20, 30, 40 and 50% of
yoghurt. The chemical, sensory and microbiological
properties of the yoghurts were determined using standard
procedures. The results showed that the pH of the yoghurt
ranged from 4.77 to 5.01. Plain yoghurt (PY) served as the
control. The protein, ash, fat and fibre contents decreased
with increase in African bush mango juice and pulp while the
moisture content increased with increase in African bush
mango juice. Micro-nutrient (vitamin A and C) increased
with increased level of African bush mango juice and pulp in
the yoghurt while (phosphorus and calcium) decreased with
increased level of African bush mango juice and pulp in the
yoghurt. The reducing sugar increased with increased level
African bush mango juice and pulp content of the formulated
yoghurt. The total viable count and lactic acid bacteria
ranged from 1.2×105 to 2.7×105 cfu/ml and 7.5×104 to
1.2×105 cfu/ml respectively. High mean values (7.95) were
obtained for the plain yoghurt (control) for all sensory
attributes (colour, flavour, taste, aftertaste, consistency and
mouth feel) therefore making the sample (PY) most
preferred sample with an overall acceptability of 7.95.
Sample (PY+ ABMP) 90:10 had the highest mean for
general acceptability (6.70) compared to the other flavoured
yoghurt samples and was second in overall preference.
Samples containing 10, 20, 30% of African bush mango juice
in yoghurt were generally acceptable while samples
containing 40 and 60% of the juice were generally
unacceptable. Samples containing 10 and 20% of African
bush mango pulp in yoghurt were generally acceptable while
samples containing 30, 40 and 50% of the juice were
generally unacceptable. There was no significant (p<0.05)
difference between the plain yoghurt and the flavoured
yoghurt sample containing 10% African bush mango juice
while the difference with the flavoured yoghurt containing
10% African bush mango pulp was significant(p<0.05).
Keywords African Bush Mango (Irvingia gabonensis),
Flavoured Yoghurt, Juice, Pulp
1. Introduction
Yoghurt is a diary product produced by bacterial
fermentation of milk (addition of a starter of active yoghurt
containing a mixed culture). The bacteria used to make
yoghurt are known as yoghurt cultures. These cultures
include Streptococcus salivarius subspecies thermophilus
and Lactobacillus delbrueckii subspecies bulgaricus.
Fermentation of lactose by these bacteria produces lactic acid,
which acts on milk protein to give yoghurt its texture and
characteristic tang [1]. The lactic acid lowers the pH, makes
it tart, causes the milk protein to thicken and acts as a
preservative since pathogenic bacteria cannot grow in acid
condition. The decrease in pH inhibits the growth of
pathogenic bacteria. The lactic acid produced is also
responsible for the characteristic flavour and aroma of
yoghurt and helps to maintain the quality of the yoghurt
during storage and packaging [2]. The partial digestion of the
milk when these bacteria ferment milk makes yoghurt easily
digestible [3]. The fermented milk could be blended with
various ingredients like fruits which provide favour and
colour.
Yoghurt is a very versatile food stuff, which is eaten both
as a food on its own or ingredient in other foods. It is a
probiotic product since it contains live active
micro-organisms which upon ingestion in sufficient number
exert health benefits beyond the inherent basic nutrition and
it can be used in marinades, dips, sauces, dressing, baked
goods, chilled and frozen dessert amongst others [4].
However milk, the major ingredient in yoghurt production,
is manufactured by a number of animals, although in terms of
commercial quantity milk from cow is the most popular.
Cow’s milk protein which comprises mainly of casein is
CITE THIS PAPER
[1] Mbaeyi-Nwaoha I. E. , Umeh L. C. , Igbokwe C. J. , Obodoechi C. M. , Okoronkwo N. C. , "Production and Quality Evaluation of
Flavoured Yoghurt from Graded Levels of Sweet Variety of African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp," Food
Science and Technology, Vol. 5, No. 2, pp. 56 - 69, 2017. DOI: 10.13189/fst.2017.050203.
Food Science and Technology 5(2): 56-69, 2017 57
most commonly used to make yoghurt but milk from goat,
water buffalo, ewe, mares, camels and yaks can also be used.
Goat milk has been reported to be a good raw material for
yoghurt processing as it compared well with cow milk in
terms of nutrient composition [5, 6]. The fermentation of
milk to yoghurt takes a relatively short period of time, 3 - 4
hours because it is done at higher temperature (42-460C) and
also uses cultures that have fast growth rates. The major
fermentation product is lactic acid, which is responsible for
coagulation of the milk caseins. Other metabolites that are
responsible for the yoghurt flavour are also produced during
the fermentation and these include diacetyl, acetaldehyde
and acetone.
In the production of yoghurt, skimmed milk is mixed with
whole or full cream milk and heated at 82 - 93C for 30 60
minutes to destroy pathogenic/spoilage micro-organisms and
to destabilize Kappa-casein. It is inoculated with a mixed
culture of Lactobacillus bulgaricus and Streptococcus
thermophilus. Initially, S. thermophilus grows rapidly to
produce diacetyl, lactic, acetic and formic acids [7]. L.
bulgaricus possesses weak protease activity which releases
peptides from the milk proteins. These stimulate the growth
of S. thermophilus [7]. The increased acidity then slows
down the growth of S. thermophilus and promotes L.
bulgaricus, which is stimulated by formate produced in the
initial stage. L. bulgaricus produces most of the lactic acid
and acetaldehyde which together with diacetyl, gives the
characteristic flavour and aroma in yoghurt [7]. To modify
certain properties of yoghurt ingredients like fruits are added
to the fermentation media to increase the organoleptic
properties. Presently, only flavoured yoghurts from exotic
fruits such as raspberry, banana, peach, vanilla, and
strawberry are commercially available.
However, there are some underutilized tropical fruits that
can be used in place of these exotic ones for instance; African
bush mango "Ugiri" (Irvingia garbonensis) can also be used
in flavouring yoghurt. African bush mango (Irvingia
garbonensis) is a fruit and a member of the family
Irvingiaceae that grows in tropical rain-forests along the
African Atlantic coast. The kernels of its seeds are used as a
thickener. African bush mango (Irvingia gabonensis) is the
Latin name of the tree grown in Central and West Africa that
produces a fruit similar to a mango and nicknamed African
mango, wild mango, dika nut, or bush mango. There are two
varieties of African bush Mango grown. One has sweet,
edible fruit (Irvingia gabonensis); the other variety has
inedible, bitter, sour fruit (Irvingia wombolu). It is very hard
to distinguish between the two trees until they bear fruit.
Both trees need up to 10 years of growth before they fruit.
They have leaves 2 1/2 to 4 inches (6 to 10 cm) long. The
sweet, edible fruit is about 2 to 3 inches wide (5 to 7.5 cm),
ripening from green to yellow. The sweet fruit is fibrous, and
can be made into juice or jam [8] and wine [9].
Meanwhile, the ripe fruit pulp of Var. gabonensis is not
just consumed for its nutrients, flavour and aroma but also
for its medicinal value. It has been claimed that consumption
of bush mango whitens the teeth [10]. The pulp of the fruit of
Irvingia gabonensis is juicy, sweet and eaten fresh. It can be
used for the preparation of juice, jelly, jam and wine. The
pulp has also been used to prepare a black dye for cloth. The
main flavour components of the fruit pulp are zingiberene
and α-curcumene, ethyl and methyl esters of cinnamic acid,
dodecanal and decanol imparting spicy-earthy, fruity and
wine-yeast flavour notes. The fruit pulp yields about 75%
juice and wine produced from it was found to be of good
colour, mouthfeel, flavour and general acceptability. The
fruit pulp is a rich source of carbohydrate and contains
significant amounts of iron, thiamine, niacin, calcium,
magnesium, fat and protein [11]. It also has many therapeutic
and nutritive properties. However, the ripe fruits are highly
perishable or susceptible to spoilage. To prevent this
spoilage and as such improve the use of the nutritive and
therapeutic properties of the fruit, African bush mango could
be used as a flavouring agent in yoghurt production. When
incorporated into yoghurt, the fruit would add to the
nutritional quality of the product by providing essential
vitamins and minerals. It would also contribute to the protein
and calorific value of the product. Addition of African bush
mango would improve the taste of the yoghurt and the
micronutrient requirements of the consumers, thus
increasing the general acceptability of yoghurt flavoured
with African bush mango.
Meanwhile, the major challenges are that yoghurt is
produced from milk which contains a reasonable amount of
live cultures mainly bacteria. The bacteria used can be
affected by other bacteria that might be on dishes and
utensils. Firstly, yoghurt is made from fermented milk. Milk
is rich in sugars, more specifically being lactose. An
environment rich in sugars is an environment that microbes
love to thrive in; thus milk is a great feast for microbes [12].
The presence of other bacteria could lead to production of
undesirable product and a product with low shelf life. Starter
culture which is the major raw material for yoghurt
production is sometimes very difficult to obtain, especially in
its active starter culture [13].
Furthermore, most Nigerian fruits are seasonal. These
tropical fruits undergo post-harvest losses because of poor
storage condition, handling, pest attack, disease and
deterioration. According to [14], processing reduces
post-harvest losses and spread the availability throughout the
year. They are abundant during their season (wet season) and
as such most of them are wasted or lost either to spoilage or
pests. To avoid these postharvest losses, these fruits (for
instance African bush mango) could be incorporated into
yoghurt as a flavouring agent. African bush mango, which is
one of the fruits neglected, is highly nutritious and
therapeutic. As such, its use as a flavourant in yoghurt
(which is the most widely consumed fermented dairy
product), would increase the number of consumers that
derive from the enormous benefits of African bush mango.
Problems could be encountered when adding the flavouring
agent if the correct amount to be added is not known [15].
58 Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of
African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
Therefore, the main aim of this study was to produce and
evaluate yoghurt, flavoured with graded levels of African
bush mango pulp.
2. Materials and Methods
2.1. Source of Raw Materials
The African bush mango (sweat variety), "ugiri" (Irvingia
gabonensis) was obtained from Nkwo Ibagwa market while
skimmed milk, starter culture (yoghurmet), sugar and
stabilizer were purchased from Ogige main market both in
Nsukka local Government area of Enugu State, Nigeria.
2.1.1. African bush mango Fruit Juice Production
The African bush mango fruit was processed according to
[16] procedure. The African bush mango fruits were sorted
to remove the bad ones after which they were washed and
peeled. Fruit juice was extracted using a juice extractor
(Pulping machine) and pasteurized for 85 C for 3 minutes.
The juice was then cooled. The flow chart for African bush
mango juice production is shown in Figure 1.
Figure 1. Production of African bush mango fruit juice. Source: Woodroff
and Luh (1986).
2.1.2. Production of African Bush Mango Flavoured Yoghurt
Figure 2. Production of flavoured yoghurt with African bush mango fruit
juice
The African bush mango fruit flavoured yoghurt was
produced as follows: the raw materials (whole milk,
carboxymethyl cellulose, CMC and sugar) were
appropriately weighed and mixed with water. The mixed
product was then homogenized to obtain a creamy and
uniform product. Pasteurization was then carried out at 85C
for 30 minutes as shown in Figure 2 to destroy the
undesirable microorganism (pathogenic and spoilage
microorganisms) in the raw materials to provide a favour
environment free from competition for the growth of the
starter culture. The product was then cooled to a temperature
of 43-46C which is the ideal growth temperature of the
starter culture. The African bush mango fruit pulp/ juice was
added. The starter inoculated. Fermentation was then carried
out for 18 hours after which the yoghurt was set. Plates 1 to 3
show the set yoghurt flavoured with African bush mango
juice and pulp.
Food Science and Technology 5(2): 56-69, 2017 59
Plate 1. Ripe African bush mango fruit
Plate 1. The formulated African bush mango flavoured yoghurt after fermentation.
PY: Plain yoghurt; ABMJ: African bush mango juice; ABMP: African bush mango pulp
A: PY (100)
B: PY+ABMJ (90:10) G: PY+ABMP (90:10)
C: PY+ABMJ (80:20) H: PY+ABMP (80:20)
D: PY+ABMJ (70:30) I: PY+ABMP (70:30)
E: PY+ABMJ (60:40) J: PY+ABMP (60:40)
F: PY+ABMJ (50:50) K: PY+ABMJ (50:50)
60 Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of
African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
Plate 2. The formulated African bush mango juice flavoured yoghurt
Plate 3. The formulated African bush mango pulp flavoured yoghurt
A=PY (100);
B=PY+ABMJ (90:10); G=PY+ABMP (90:10)
C=PY+ABMJ (80:20); H= PY+ABMP (80:20)
D= PY+ABMJ (70:30); I=PY+ABMP (70:30)
E=PY+ABMJ (60:40); J=PY+ABMP (60:40);
F=PY+ABMJ (50:50); K=PY+ABMJ (50:50.
Food Science and Technology 5(2): 56-69, 2017 61
2.2. Sample Analyses
2.2.1. Determination of Moisture Content of the Formulated
Flavoured Yoghurt
The moisture content of the samples was determined using
the hot oven method of [17]. Two millilitres (2 ml) of each
sample was put into a washed and dried crucible dish and
placed in a Phoenix oven (Preiser model, New York, USA) at
a temperature of 70-800C for 2 hours and at 100-105 0C until
the weight is constant. The samples were cooled in a
desiccator and weighed. The weight loss was obtained as the
moisture content and was calculated as:
23
21
100
% WW
Moisture content WW
×
=
Where; W1 = initial weight of empty crucible; W2 = weight
of crucible + sample before drying; W3 = final weight of
crucible + sample after drying
2.2.2. Determination of Crude Protein Content of the
Formulated Flavoured Yoghurt
The crude protein of the samples was determined by the
semi-micro Kjeldahl technique described by [17]. A
millilitre (1.0ml) of the sample was put into a Kjeldahl flask.
Three grams (3g) anhydrous sodium sulphate and one (1g) of
hydrated copper sulphate (catalyst) were added into the flask.
Then, 20 ml of concentrated tetraoxosulphate (IV) acid
(H2SO4) was added to digest the sample. The digestion
continued under heat until a solution was observed. The clear
solution was then cooled and made up to 100 ml with
distilled water and a digest of about 5 ml was collected for
distillation. Then, 5 ml of 60% sodium hydroxide (NaOH)
was put into the distillation flask and distillation was allowed
to take place for some minutes. The ammonia distilled off
was absorbed by boric acid indicator and this was titrated
with 0.01M hydrochloric acid (HCl). The titre value of the
end point at which the colour changed from green to pink
was taken. The crude protein was calculated as:
0.0001401 100 6.25
% 5
T
Crude protein W
×× ×
=×
Where; T= titre value; W= weight of sample dried
2.2.3. Determination of Crude Fiber Content of the
Formulated Flavoured Yoghurt
Crude fiber was dome using the method of [18]. Two
millilitres (2ml) of the sample was hydrolysed in beaker with
299ml of 1.25% sulphuric acid (H2SO4) and boiled for 30
minutes. The mixture was filtered, washed with hot distilled
water and boiled again for 30 minutes with 200 ml of 1.25%
of NaOH. The digested sample was also washed with 1%
HCl acid to neutralize the NaOH and then with hot distilled
water for several times. The residue was put into weighed
crucible and dried at 100 0C for 2 hours in an air oven, after
drying the sample was cooled, weighed and then transferred
into a muffle furnace (Coleman WAKMO11379 New York,
USA) for burning at 5000C for 5 hours. The loss in weight
was taken and percentage crude fiber was calculated as
follow
( )
100
Percent crude fiber
Loss in weight g after ignition
Weight of the original sample
=
= ×
2.2.4. Determination of Crude Fat Content of the Formulated
Flavoured Yoghurt
The solvent extraction method as described by [17] was
used. The extraction flasks were washed with petroleum
ether, dried and cooled and weighed. Five millilitres (2 ml)
of the sample were weighed into the extraction thimble. It
was then placed back in the Soxhlet apparatus. The washed
flask was filled to about three quarter of its volume with
petroleum ether (that has the boiling temperature range of
40-600C). The apparatus was then set-up and extraction
carried out for a period of 4 - 6 hours after which complete
extraction was made. The petroleum ether was recovered
leaving only oil in the flask at the end of the extraction. The
oil in the extraction flask was dried in the oven, cooled and
finally weighed. The fat content was expressed as a
percentage of raw materials. The difference in weight of
empty flasks and the flask with oil content which was
calculated as:
% 100
CB
Fat content A
= ×
Where; A = Weight of sample; B = Weight of empty flask;
C = Weight of flask + Oil.
2.2.5. Determination of Ash Content of the Formulated
Flavoured Yoghurt
The ash content of the sample was determined by the
method recommended by [17]. A silica dish was heated to
about 60 0C, cooled in a desiccator and weighed. Five
millilitres (5 ml) of the sample was put into the silica dish
and transferred to the furnace. The temperature of the
furnace was then allowed to reach about 525 0C after placing
the dish in it. The temperature was maintained until
whitish-grey colour was obtained indicating that all the
organic matter content of the sample has been destroyed. The
dish was then brought out from the furnace and cooled in the
desiccator and re-weighed. The percentage ash content was
the calculated as
Where: A = weight of empty dish; B = weight of empty
dish + sample before ashing; C = weight dish + ash
2.2.6. Determination of Carbohydrate of the Formulated
Flavoured Yoghurt
Carbohydrate was determined as the nitrogen free
extraction calculated by difference as described by [19]. The
62 Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of
African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
formula below was used:
% Carbohydrate = 100% - % (protein +
+ fat + fibre + ash + moisture)
2.2.7. Determination of pH of the Formulated Flavoured
Yoghurt
The pH was determined using a pH meter as described by
[17]. The electrode was dipped into the yoghurt solution and
then the pH was recorded.
2.2.8. Determination of Total Titrable Acidity (TTA) of the
Formulated Flavoured Yoghurt
The total titrable acidity was determined by the method
described by [17]. Then, 10 ml of the sample was measured
into a conical flask and about 3 drops of phenolphthalein
indicator was added to the sample and titrated with 0.1 N
sodium hydroxide (NaOH) until colour change was observed.
The end point was taken and the TTA expressed as % lactic
acid was given as
()( )
%
0.09 100
TTA as lactic acid
m NaOH N NaOH
Volume of sample
=
× ××
=
2.2.9. Determination of Vitamin A Content of the Formulated
Flavoured Yoghurt
Vitamin A content was determined according to [20]
procedure. Then, 5 ml sample was first saponified using an
alcoholic solution of potassium hydroxide in the presence of
pyrogallol. This freed the vitamins from the food matrix and
converted any retinyl ester to retinol. The unsaponified
matter containing vitamin A was extracted using a mixture of
diethyl ether and petroleum spirit. The extract was
evaporated under nitrogen and the residue was dissolved in
methanol. The extract was chromatographed using a reverse
phase octadecyl silane (ODS) column with the mobile phase
consisting of 95% acetonitrile with 5% water. The separated
retinol was then quantified using a UV absorbance detector
at 328 nm.
2.2.10. Determination of Vitamin C Content of the
Formulated Flavoured Yoghurt
The ascorbic acid was determined using the method of
[21]. Then, two millilitres (2ml) of the sample was weighed
and 100 ml of distilled water was added to it. It was then
filtered to get a clear solution. Also, 10 ml of the clear
solution was pipette into small flask in which 2.5 ml acetone
was added. It was then titrated with indophenols solution (2,
6-dicholorophenolindophenol) to a faint pink colour which
persists for 15 seconds. The vitamin C content was
calculated as:
Vitamin C (mg/ 100ml of sample) = 20 x V x C
Where: V= indophenols solution in titration (ml); C= mg
Vitamin C/ml indophenols
2.2.11. Determination of Calcium Content of the Formulated
Flavoured Yoghurt
It was determined by titration method according to [18].
Then, two millilitres (2 ml) of the ashed sample was diluted
with 3 ml of distilled water and 1 ml of 50% ammonium
oxalate. One drop of methyl red indicator was made alkaline
with ammonia drops and drops of glacial acetic acid until
colour changes to pink. It was stood for 4 hours and
centrifuged for 5 minutes, followed by decantation of the
supernatant. One millilitre (1 ml) of hydrogen sulphate was
added to the residue which was diluted with 4 ml of distilled
water. The solution was boiled and titrated with 0.02 N
potassium permanganate.
2.2.12. Microbial Analysis of the Formulated Flavoured
Yoghurt
2.2.12.1. Determination of Total Viable Count of the
Formulated Flavoured Yoghurt
One Ringer tablet was dissolved in distilled water (500 ml).
The clear solution formed was sterilized by autoclaving for
15 minutes at 1210C and 15lb pressure. The Ringer solution
was allowed to cool completely to a temperature of about
28±20C. The total viable count test was carried out using [22].
Using of sample and sterilized quarter strength ringer
solution as diluents, 1 ml of the sample and 9ml ringer
solution was made serial dilutions (10-4). The diluted sample
was pipetted into a marked Petri dish, swirled to mix and
incubated at the temperature of about 37°C for 24h. After
incubation, the number of colonies was counted and
represented as colony forming unit per millilitre.
2.2.12.2. Determination of Lactic Acid Bacteria (LAB) of the
Formulated Flavoured Yoghurt
The microbial count of lactic acid bacteria (LAB) in the
formulated yoghurt was determined using deMan Rogosa
Sharpe (MRS) agar (CM 361) according to [23]. Samples
were serially diluted in duplicates using the surface pour
plate method. The plates were incubated under anaerobic
conditions at 37
C for 48 hours.
2.3. Sensory Evaluation of the Formulated Flavoured
Yoghurt
Sensory properties of the samples were evaluated by 20
semi-trained panelists who are conversant with yoghurt and
consisting of staff and students of University of Nigeria,
Nsukka for various sensory attributes (colour, taste, flavour,
texture and overall acceptability). The extent of differences
between the yoghurt samples for each sensory quality was
measured on a nine-point Hedonic scale, where “9”
represents extremely like and “1” represents extremely
dislike [24].
2.4. Data Analysis and Experimental Design
Food Science and Technology 5(2): 56-69, 2017 63
Data analyses were calculated using one-way Analysis of
Variance (ANOVA) laid on a completely randomized design.
Significant means were separated by Duncan’s new multiple
range test and significance was accepted at (P< 0.05) using
SPSS (Statistical Package for Social Sciences) version 20
according to [25].
3. Results and Discussion
3.1. Proximate Composition of Yoghurt Flavoured with
Graded Levels of African bush mango Juice and
Pulp
Table 1 shows the proximate composition (%) of yoghurt
flavoured with graded levels of African bush mango juice
and pulp. The moisture content of the flavoured yoghurt
sample ranged from 85.28 - 87.14% (Table 1). There was no
significant (p < 0.05) difference in the moisture contents of
samples with sample PY+ABMJ (100: 0, 90:10 and 80:20),
respectively. However, sample PY+ABMP (80:20) had the
lowest moisture content while the sample PY+ABMJ (70:30)
had the highest moisture content. This showed that the
moisture levels decreased with increase in the concentration
of African bush mango pulp added and increased with
increase in the concentration of African bush mango juice
added except for sample PY+ABMJ (80:20). This could be
caused by alteration in the volume of African bush mango
juice added. The decrease in the high moisture content of the
formulated yoghurt sample could be as result of reduction in
volume of yoghurt with increase in the volume of African
bush mango juice. The moisture content of sample with
ranged 85.28-87.14% observed in this study agreed with the
moisture content sample with range 80.45-90.47% for
formulated yoghurt flavored with solar-dried bush mango
pulp reported by [26].
Table1 showed that the crude protein ranged from 1.29 -
3.52% with plain yoghurt having the highest crude protein
content. The protein content of the flavoured yoghurt
decreased with increase in the level of African bush mango
juice and pulp added. This decrease could be attributed to the
lower protein content of African bush mango juice and pulp
compared to milk. The protein content of the plain yoghurt
agreed with the range (3.4 - 5.6%) reported by [27]. The
protein content of the plain yoghurt sample PY+ABMJ
(100:0) observed in this study concurred with that of the
protein content of 3.5 for plain soymilk yoghurt reported by
[28].
Table 1 showed that the crude fat ranged from 0.14-0.70%
with plain yoghurt having the highest crude fat content. The
maximum crude fat was seen in plain yoghurt sample
PY+ABMJ (100:0) and fat content was found to gradually
decrease with addition of the fruit juice and pulp. [29]
reported that intake of African bush mango supplement boost
the breakdown of fats. [29] reported that intake of African
bush mango supplement boost the breakdown of fats.
Generally, African bush mango contains low level of fat
therefore the addition of juice and pulp might have decreased
the fat percent of flavoured yoghurt. The difference in fat
percentage between plain yoghurt and flavoured yoghurts
were significant (p < 0.05) while the fat content in flavoured
yoghurt sample PY+ABMJ (70:30) and PY+ABMP (90:10)
were not significantly (p < 0.05) different. The fat content of
yogurts varies depending on the product, ranging from
approximately 10% fat for full fat Greek style yogurts, 3%
fat for whole milk yogurts, 1.7% fat for low fat yogurts and
non-fat varieties containing less than 0.3% fat [30].
Therefore, the formulated sweet variety of African bush
mango juice and pulp flavoured yoghurt which had a fat
content ranging from 0.14 to 0.70% could be referred to as
non-fat yoghurt. The fat content of the samples observed in
this study concurred with the range of 0.15-0.80% for
flavoured yoghurt with tamarind reported by [31].
Table 1 showed that the ash content ranged from 0.18% in
sample PY+ABMJ (80:20) and PY+ABMJ (70:30) to 0.30%
in sample PY+ABMJ (100:0). The ash content of African
bush mango juice flavoured yoghurt samples were somewhat
lower than that of plain yoghurt but differences in ash
content between flavoured yoghurt sample PY+ABMJ
(80:20) and PY+ABMJ (70:30) was not significant (p < 0.05).
Same goes with sample PY+ABMP (90:10) and PY+ABMP
(80:20). The ash content differed significantly (p < 0.05)
from range (1.21-1.38%) for flavoured yoghurt with soursop
reported by [32]. The ash content of the samples was
observed to decrease with increasing level of African bush
mango juice and pulp added. This could be as attributed to
the decrease in the volume of milk using African bush mango
juice and pulp as a substitute. According to [33] ash could be
residue remaining after water and organic matter have been
removed by heating in the presence of oxidizing agents,
which provides a measure of the total amount of minerals
present within a food. Milk is highly rich in minerals some of
which are not found in African bush mango juice and pulp.
This; therefore; could have instigated that the decrease in ash
content with the addition of African bush mango juice and
pulp. However, this decrease in ash content was minimal.
Table 1 revealed that the fibre content ranged from 1.26%
in sample PY+ABMJ (70:30) to 2.87% in sample
PY+ABMP (90:10). There was no significant (p < 0.05)
difference in the fibre contents of samples with PY and
PY+ABMP ratios of 100:0 and 70:30, respectively, same
goes with flavoured yoghurt samples PY+ABMJ (90:10) and
(80:20).
Carbohydrate content ranged from 8.00% in sample PY
(100:0) to 11.25% in sample PY+ABMP (80:20) as shown in
Table 1. The carbohydrate content increased with increase in
the concentration of the African bush mango pulp in the
flavoured yoghurt. The carbohydrate content of the African
bush mango pulp flavoured yoghurt sample (PY+ABMP)
80:20 was the highest. This could probably be due to the fact
that African bush mango pulp has high carbohydrate content
15.63g in 100g [12].
Food Science and Technology 5(2): 56-69, 2017 65
Tab le 1. Proximate composition (%) of African bush mango juice and pulp flavoured yoghurt samples
Sample Moisture Crude protein Ash Crude fat Crude fibre Carbohydrate
PY (100:0) 86.18b± 0.04 3.52d±0.04 0.30d±0.02 0.70e±0.01 1.31a±0.01 8.00ab± 0.02
PY+ABMJ (90:10) 86.19b ±0.02 3.29c±0.02 0.21b±0.01 0.50d±0.01 1.48b±0.06 8.34b±0.01
PY+ABMJ (80:20) 86.16b± 0.10 2.42b±0.00 0.18a±0.00 0.44c±0.00 1.45b±0.00 9.35d±0.11
PY+ABMJ (70:30) 87.14d± 0.10 2.42b±0.00 0.18a±0.00 0.26b±0.01 1.26a±0.06 8.81c±0.21
PY+ABMP (90:10) 86.57c ± 0.08 2.43b±0.10 0.26c±0.00 0.24b±0.01 2.87d±0.02 7.65a±0.18
PY+ABMP (80:20) 85.28a± 0.21 1.29a±0.00 0.25c±0.01 0.14a±0.00 1.80c±0.05 11.25e.±0.27
Values are mean ± standard deviation of duplicate readings. Values on the same column with different superscript are significantly different (p < 0.05).
Key: PY= Plain yoghurt; ABMJ=African bush mango juice; ABMP=African bush mango pulp
Tab le 2. Selected vitamins and mineral composition of African bush mango juice and pulp flavoured yoghurt
Sample
Vitamin A (IU)
Vitamin C (mg/100g)
Phosphorus (mg/100g)
Calcium (mg/100g)
PY+ABMJ (100:0)
20.88a ±0.47
22.20a±0.01
73.59f±0.52
62.14f±0.21
PY+ ABMJ (90:10)
60.60c±1.98
24.80b±0.05
43.83b±0.10
38.67e±0.00
PY+ ABMJ (80:20)
72.78d±2.17
25.54c±0.16
42.39b±0.55
35.96d±0.63
PY+ ABMJ (70:30)
98.71f±1.16
27.79d±0.18
32.44a±0.36
33.57c±0.99
PY+ ABMP (90:10)
26.60b±2.90
22.58a±0.18
65.71e±0.03
19.60b±0.41
PY+ ABMP (80:20)
79.10e±3.25
22.60a±0.55
64.61d±0.55
16.99a±0.21
Values are mean ± standard deviation of duplicate readings. Means on the same column with different superscripts are significantly different (p<0.05).
KEY: PY= Plain yoghurt; ABMJ=African bush mango juice; ABMP= African bush mango Key: PY= Plain yoghurt; ABMJ=African bush mango juice;
ABMP=African bush mango pulp
3.2. Micro-nutrient Composition of Yoghurt Flavoured
with Graded Levels of African bush mango Juice
and Pulp
The selected vitamins and minerals composition of the
flavoured yoghurt samples are shown in Table 2. It shows the
effect of African bush mango flavour on micronutrients
content of the formulated sample. The vitamin A content
ranged from 26.60- 98.71 IU. The plain yoghurt sample
PY+ABMJ (100:0) had the lowest vitamin A content while
sample PY+AMBJ (70:30) had the highest value. However,
there was significant (p < 0.05) difference in the vitamin A
content of the samples PY (100:0) and the formulated
flavoured yoghurt samples. The vitamin A content increased
with increase in the addition of African bush mango juice
and pulp compared to the vitamin A content of the plain
yoghurt sample PY+ABMJ (100:0). This is probably due to
the vitamin A content of African bush mango juice and pulp.
The result range (26.60 - 98.71 IU) observed in this study
concurred with the value range (35.02-280.18 IU) reported
by [26]. The result also showed that the African bush mango
juice contained more vitamin A than its pulp.
The ascorbic acid (vitamin C) content (Table 2) had a
range between 22.20 mg/100 g in plain yoghurt and
27.79mg/100g in the sample flavoured with 30% African
bush mango juice. The ascorbic acid content increased with
the addition of African bush mango juice and pulp. This is
probably due to the high ascorbic acid content of African
bush mango juice and pulp. The flavoured yoghurt samples
with African bush mango juice contained higher amount of
vitamin C compared those flavoured with the pulp. Studies
had shown that ascorbate favours iron absorption by
reducing the inorganic iron III (ferric) complexes in food to
iron II (ferrous), a form in which it is more readily absorbed
according to [34]. Vitamin C (ascorbic acid) content of
formulated yoghurt samples flavored with solar- dried bush
mango pulp reported by [26] was far lower than that obtained
in this study.
Phosphorus (P) content is ranged from 32.44 mg/100g in
the sample containing with 30% African bush mango juice to
73.59 mg/100g in sample plain yoghurt (Table 2).
Phosphorus content decreased with increase in concentration
of the African bush mango juice content of the yoghurt. Also,
phosphorus decreased with increase in concentration of
African bush mango pulp compared with the plain yoghurt.
The plain yoghurt had the highest phosphorus content (73.59
mg/100g). There was significant (p < 0.05) difference in
phosphorus content of the flavoured samples. Table 2
showed that the calcium (Ca) content of the samples ranged
between 16.99 mg/100g of the formulated yoghurt with
African bush mango pulp to 62.14 mg/100mg. Plain yoghurt
had the highest calcium content. There was significant (p <
0.05) difference in the calcium content of the plain yoghurt
sample and the samples. The lower level of calcium in the
samples containing African bush mango juice and pulp could
be attributed to the substitution of milk with African bush
mango juice and pulp which has lower calcium content. [35]
reported that, African bush mango juice had a calcium
content of 4.0 mg/100 g and 20 mg/100 g reported by [8].
Plain Yoghurt however contains 120.8 mg of calcium per
100 g [36].
Food Science and Technology 5(2): 56-69, 2017 65
3.3. Physico-chemical Properties of Yoghurt Flavoured
with Graded Levels of African bush mango Juice
and Pulp
Table 3 shows some selected physico-chemical of yoghurt
flavoured with graded levels of African bush mango juice
and pulp. Table 3 showed that the pH of the flavoured
yoghurt samples ranged from 4.77 in sample PY+ABMJ
(100:0) and 5.01 in sample PY+AMBJ (70:30). The
flavoured yoghurt samples had slightly higher pH values
than plain yoghurt but this difference was not significant (p <
0.05). Addition of African bush mango juice and pulp
slightly lowered the acidity of the yoghurts and this was
however in contrast with the report given by [37] whose
results indicated that the use of indigenous fruits as flavours
resulted in a slight increase in the acidity of yoghurts. It was
also observed that addition of African bush mango juice
resulted to a more less acidic yoghurt compared to that of the
African bush mango pulp this, might be attributed to the pH
of the African bush mango juice which was observed to be
slightly acidic. The pH value of formulated yoghurt with
African bush mango juice concentration of 30% agreed with
the value (5.49) reported by [35]. The decrease in acidity
could probably be attributed to fact that the acidity of fruits
decrease as they ripen.
Total solids increased with increase in concentration of the
African bush mango pulp in yoghurt. Sample PY+AMBP
(80:20) had the highest total solids content (14.24%). [31]
reported total solids values for yoghurts flavoured with
tamarind ranging from (13.12 - 21.78%). Similar results
ranged from 13.00% to 14.24% were obtained from this
study. The total solids value obtained in this study was lower
than that reported on yoghurt flavoured with solar-dried bush
mango (Irvingia gabonensis) pulp by [26]. This could be
attributed to the nature of the African bush mango used in
this study (juice and wet pulp). The difference between the
total solids of the formulated yoghurt sample and the plain
yoghurt sample was not significant (p < 0.05). Furthermore,
moisture content in Table 1 decreased with increase in the
total solids. For instance sample PY+ABMP (80:20) in Table
1 had lowest moisture content and the highest total solids
content in Table 3.
Table 3 showed that the titrable acidity of samples
decreased with increase in the pH values. Titrable acidity
ranged from 0.76% in sample PY+ABMJ (70:30) to 0.91%
in sample PY+ABMP (90:10). [32] reported titrable acid
values for soursop pulp flavoured yoghurts ranging from
0.69 - 0.83%. Similar results 0.76 - 0.91% were obtained
from this study.
Tab le 3. Physico-chemical properties of African bush mango flavoured yoghurt samples
Sample pH Titrable acidity Total solids (%) Reducing sugar(%)
PY+ABMJ 100:0 4.77a±0.11 0.85cd±0.01 13.85ab±0.07 9.33a±0.07
PY+ ABMJ (90:10) 4.78a±0.18 0.83bc±0.00 13.85ab±0.02 9.85ab±0.02
PY+ ABMJ (80:20) 4.79a±0.27 0.80b±0.01 13.84ab±0.10 10.80bc±0.10
PY+ ABMJ (70:30) 5.01a±0.21 0.76a±0.02 13.00a±0.10 10.20abc±0.10
PY+ ABMP (90:10) 4.69a±0.12 0.91e±0.01 13.55ab±0.07 10.90c±0.28
PY+ ABMP (80:20) 4.80a±0.01 0.88de±0.02 14.24b±0.90 12.56d±0.10
Values are mean ± standard deviation of duplicate readings. Means on the same column with different superscripts are significantly different (P<0.05).
Key: PY= Plain yoghurt; ABMJ=African bush mango juice; ABMP= African bush mango pulp
66 Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of
African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
3.4. Microbial Count (cfu/ml) of Yoghurt Flavoured with
Graded Levels of African bush mango Juice and
Pulp
Table 4 shows the microbial population of the formulated
products. The samples showed a lactic acid bacteria count of
between 1.2×105 - 7.5×104 cfu/ml. The lactic acid bacteria
(LAB) count was also observed to decrease with increase in
African bush mango juice and pulp concentration. This could
be as a result of the decrease in milk content which contains
the lactose which acts as a substrate for the growth and
multiplication of the LAB. This decrease could also be
responsible for the increase in pH observed.
As shown in Table 4 the samples showed a total viable
count of between 1.2×105cfu/ml in sample PY+ABMP
(80:20) to 2.7×105 cfu/ml in plain yoghurt. The total viable
count was observed to decrease with increase in African bush
mango juice and pulp. This could attribute to the
antimicrobial effect of African bush mango. African bush
mango have inhibitory activity against several bacteria and
fungi with its potential mechanisms action which include
membrane disruption by terpenoids and inactivation of
microbial adhesion, enzymes, and cell envelope transport
proteins by ellagic acids-like compound [38].
3.5. Sensory Scores for the Formulated Yoghurt
Flavoured with Graded Levels of African bush
mango Juice
Table 5 shows the sensory scores of the yoghurt flavoured
with graded levels of African bush mango juice. The mean
scores of colour ranged from 3.95 in the sample containing
with 50% African bush mango juice to 8.10 in plain yoghurt.
Plain yoghurt had the highest score for colour and there was
significant (p < 0.05) difference in the colour of the plain
yoghurt sample and the flavoured yoghurt samples. The
sample containing 50% African bush mango juice had the
lowest colour value (3.95)
Tab le 4. Lactic acid bacteria (LAB) and total viable count (TVC)
Sample TVC(cfu/ml) LAB (cfu/ml)
PY+AMBJ(100:0) 2.7×105 1.2×105
PY+AMBJ (90:10) 2.0×105 9.1×104
PY+AMBJ(80:20) 1.9×105 8.5×104
PY+AMBJ(70:30) 1.6.×105 7.5×104
PY+AMBP(90:10) 2.4×105 7.5×104
PY+AMBP(80:20) 1.2×105 3.8×104
Key: PY= Plain yoghurt; ABMJ= African bush mango juice; ABMP= African bush mango juice pulp; LAB= Lactic acid bacteria TVC= Total viable count
pH of deManRogosa Sharpe (MRS) Agar (CM 361) =6.2±0.2
pH of Nutrient agar media= 7.4±0.2
Tab le 5. Sensory scores of yoghurt flavoured with graded levels of African bush mango juice
Sample Colour Flavour Taste Aftertaste Consistency Mouthfeel Overall Acceptability
PY+ABMP (100:0) 8.10d±1.02 7.75d±0.97 7.75e±0.91 7.35c±1.04 6.95c±0.83 7.50d ±0.89 7.95e ±0.89
PY+ABMP ( 90:10) 6.70c±1.26 6.50c±1.43 6.35e±1.46 6.65c±1.18 6.60c±1.57 6.25c ±1.55 6.70d ±1.30
PY+ABMP (80:20) 6.05c±1.43 5.25c±1.29 5.00e±1.38 4.95b±1.50 5.90bc±1.33 4.90b ±1.44 5.30c ±1.49
PY+ABMP (70:30) 4.30b±1.56 4.75bc±1.74 4.45e±1.50 4.70b±1.38 5.15ab±1.87 3.65a ±1.30 4.37c ±1.57
PY+ABMP (60:40) 3.60a±1.67 4.40ab±1.75 3.75e±1.33 4.55b±1.53 4.50a±2.50 3.35a ±1.35 3.95ab ±1.70
PY+ABMP ( 50:50) 3.00a±2.00 4.175a±1.99 2.80e±1.32 3.35a±1.79 4.20a±2.50 3.00a ±1.92 3.30a ±1.92
Values are mean ± standard deviation of 30 panelists. Means on the same column with different superscripts are significantly different (P<0.05).
Key: PY= Plain yoghurt; ABMJ=African bush mango juice; ABMP= African bush mango pulp
Food Science and Technology 5(2): 56-69, 2017 67
The scores for flavour ranged from 3.50 in sample
PY+AMBJ (50:50) to 7.75 in plain yoghurt. Plain yoghurt
had the highest score (7.75) for flavour. The preference for
the flavour of the products reduced with increasing level of
African bush mango juice addition. Plain yoghurt had the
highest score for flavour but there was no significant (p<0.05)
difference in the flavour of the plain yoghurt sample and the
sample containing 10% African bush mango juice.
The scores for taste ranged from 3.30 in sample
PY+AMBJ (50:50) to 7.75 in sample plain yoghurt. Plain
yoghurt had the highest score (7.75) for taste. Plain yoghurt
had the highest score for taste but there was significant (p <
0.05) difference in the taste of the plain yoghurt sample and
the samples.
The values for consistency ranged from 4.30 in sample
PY+ABMJ (50:50) to 6.95 in sample plain yoghurt. Plain
yoghurt had the highest score (6.95) for consistency. The
preference for the consistency of the products reduced with
increasing level of African bush mango juice addition. Plain
yoghurt had the highest score for consistency but there was
no significant (p < 0.05) difference in the consistency of the
plain yoghurt sample and the sample containing 10% African
bush mango juice.
The mouthfeel ranged from 4.15 in PY+ ABMJ (50:50) to
7.50 in the plain yoghurt sample. The results show that there
was no significant (p < 0.05) difference between mouth feel
and general acceptability of the plain yoghurt and flavoured
sample with containing 10% African bush mango juice.
The mean scores for overall acceptability ranged from
3.60 in sample PY+AMBJ (50:50) to 7.95 in plain yoghurt.
High mean values (7.95) were obtained for the plain yoghurt
for all sensory attributes (colour, flavour, taste, aftertaste,
consistency and mouth feel) therefore making it the most
preferred sample with an overall acceptability of 7.95.
Sample PY+ ABMJ (90:10) had the highest mean for general
acceptability (7.35) compared to the other flavoured yoghurt
samples and was second in overall preference. Low means
were observed in the samples containing 40 and 50% African
bush mango juice for all sensory attributes (colour, flavour,
taste, aftertaste, consistency and mouth-feel) therefore
making them the most disliked samples with an overall
acceptability of 4.30 and 3.60 respectively.
The results of the sensory evaluation implied that yoghurt
flavoured with up to 30% African bush mango juice could be
produced without having a negative impact on the consumer
acceptability of the product. Similar acceptance of flavoured
yoghurt using indigenous fruits were obtained using beetroot
by [39], soursop [40], cashew [41] as well as carrot,
pineapple, and spiced yoghurts using ginger and pepper fruit
[42]. These quality findings may be useful for yoghurt
industries to produce new variety of yoghurts. Plain yoghurt
was more highly rated than African bush mango juice
flavoured yoghurt in all the sensory attributes. This could be
attributed to the sweet to bitter taste accustomed to African
bush mango rather than the African bush mango flavoured
yoghurts that had never been used in yoghurt production.
3.5.1. Sensory Scores of Yoghurt Flavoured with Graded
Levels of African bush mango Pulp
Table 6 shows the sensory scores of the yoghurt flavoured
with graded levels of African bush mango. The mean scores
for overall acceptability ranged from 3.30 in sample
PY+AMBP (50:50) to 7.95 in plain yoghurt. High mean
values (7.95) were obtained for the plain yoghurt for all
sensory attributes (colour, flavour, taste, aftertaste,
consistency and mouthfeel) by making it the most preferred
sample with an overall acceptability of 7.95. Sample PY+
ABMJ (90:10) had the highest mean for general acceptability
(6.70) compared to the other flavoured yoghurt samples and
was second in overall preference. Low means were observed
in the samples containing 30, 40 and 50% African bush
mango juice for all sensory attributes (colour, flavour, taste,
aftertaste, consistency and mouth-feel) thereby making them
the most disliked samples with an overall acceptability of
4.37, 3.95% and 3.30 respectively. The value for overall
acceptability of 6.70 for flavoured yoghurt containing 10%
African bush mango pulp was not significantly different (p <
0.05) from the value (6.75) reported for solar-dried African
bush mango pulp flavoured yoghurt [26]. The results of the
sensory evaluation implied that yoghurt flavoured with up to
20% African bush mango pulp could be produced without
having a negative impact on the consumer acceptability of
the product.
Tab le 6. Sensory scores of yoghurt flavoured with graded levels of African bush mango pulp
Sample Colour Flavour Taste Aftertaste Consistency Mouthfeel Overall Acceptability
PY+ABMJ (100:0) 8.10e±1.02 7.75c±0.97 7.75e±0.91 7.35d±1.04 6.95d±0.83 7.50c ±0.89 7.95d ±0.89
PY+ ABMJ ( 90:10) 7.30d ±0.86 6.90c±1.25 6.90c±1.25 7.35d±1.04 6.55cd±1.19 7.00c ±1.30 7.35d ±0.98
PY+ ABMJ (80:20) 5.85c±1.18 5.15b±1.18 4.95b±1.53 5.35c±1.34 5.70bc±0.98 5.80b ±0.95 6.200c ±0.83
PY+ ABMJ (70:30) 5.15bc±1.18 4.65a±1.39 4.65b±1.39 4.60bc±1.50 5.65bc±1.57 5.35b±1.35 5.15b±1.23
PY+ ABMJ (60:40) 4.60ab±1.53 4.05a±1.50 3.75a±1.25 4.10ab±1.44 4.70ab±1.92 4.90ab ±1.37 4.30a ±1.63
PY+ ABMJ (50:50) 3.95a±1.31 3.95a±1.76 3.30a±1.26 3.50a±1.64 4.30a±2.36 4.15a ±2.13 3.60a ±1.46
Values are mean ± standard deviation of 30 panelists. Means on the same column with different superscripts are significantly different (P<0.05).
Key: PY= Plain yoghurt; ABMJ=African bush mango juice; ABMP= African bush mango pulp
68 Production and Quality Evaluation of Flavoured Yoghurt from Graded Levels of Sweet Variety of
African Bush Mango "Ugiri" (Irvingia gabonensis) Juice and Pulp
4. Conclusions
The result of this study showed that addition of African
bush mango juice and pulp to yoghurt as flavouring agent
improved the physicochemical, proximate and sensory
properties of the formulated product. The flavoured yoghurt
contained a good amount of vitamin C, which is vital in iron
metabolism and subsequent fight against iron deficiency
anaemia (IDA). This could contribute significantly in
improving the vitamin C intake of the populace in Nigeria.
The use of underutilized natural flavour (African bush
mango fruit) helps in creating a variety of yoghurt and also
increasing the nutritional as well as medicinal value of
yoghurt. The addition of African bush mango juice and pulp
to yoghurt had a positive impact on the proximate,
micronutrient and sensory properties of the formulated
product. From the results obtained in this study, it can be
concluded that the yoghurt blended with African bush mango
juice at a ratio of 90:10 was the most preferred among the
flavoured yoghurt samples formulated. It had a general
acceptability of 7.15 while the blend with African bush
mango pulp at a ratio of 90:10 was the most preferred among
the flavoured yoghurt.
Based on the result, it is recommended that more research
be carried out on the African bush mango (mesocarp) in
order to improve its sensory characteristics and increasing
the shelf life of the fruit juice and pulp as flavouring agents.
Consumers should also be enlightened on the nutritional and
health benefits of African bush mango as a strategy for food
diversification and domestication of African bush mango.
Further studies should also be done on the shelf stability of
African bush mango flavoured yoghurt.
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... difference in the smell of the plain soya bean yoghurt sample and the flavoured samples. The result for smell obtained in this study is also similar to the result obtained for 15% mango fruit juice yoghurt reported by Getenesh et al., [11] ...
... The result of this study is in agreement with those reported by (Osundahunsi et al., 2007;Getenesh et al., 2017). However, it was in contrast with the findings of (Ndabikunze et.al, 2017; Mbaeyi et a.,l 2017) [13,11]. Vishal et al., (2014) [8] also observed that the scores increased to a certain point, then declined on further addition of the mango pulp. ...
... According to Abdallah and Mohamed (2017) mangoes are preferably used as flavouring material in the manufacture of yoghurt. Similarly, (Getenesh et al., 2017) [11] observed the same trend. ...
Article
Full-text available
Soya bean yoghurt produced from soya milk using standard procedures was flavoured with 0%, 5%, 10% and 15% Julie mango pulp and labeled SC (Control), F1, F2, and F3 respectively. The results from the analysis with a significant difference (p<0.05) showed that the pH of the soya bean yoghurt ranged from 3.40 to 3.50. The scores obtained for sensory attributes (colour, smell, taste, sourness and flavor) of the Julie mango pulp flavoured soya bean yoghurt were compared with that of the plain soya bean yoghurt sample. The sensory evaluation result showed a mean score of 5.00 as overall acceptability for sample F3 for all sensory attributes (colour, smell, taste, sourness and flavor) thereby making it the most preferred sample by the panelists. Sample F2 had an overall acceptability mean score of 4.20 for all sensory attributes making it second in overall preference. Sample F1 has an overall acceptability mean score of 4.00, while Sample SC was the least preferred with an overall acceptability mean score of 2.80.
... difference in the smell of the plain soya bean yoghurt sample and the flavoured samples. The result for smell obtained in this study is also similar to the result obtained for 15% mango fruit juice yoghurt reported by Getenesh et al., [11] ...
... The result of this study is in agreement with those reported by (Osundahunsi et al., 2007;Getenesh et al., 2017). However, it was in contrast with the findings of (Ndabikunze et.al, 2017; Mbaeyi et a.,l 2017) [13,11]. Vishal et al., (2014) [8] also observed that the scores increased to a certain point, then declined on further addition of the mango pulp. ...
... According to Abdallah and Mohamed (2017) mangoes are preferably used as flavouring material in the manufacture of yoghurt. Similarly, (Getenesh et al., 2017) [11] observed the same trend. ...
Article
Full-text available
Soya bean yoghurt produced from soya milk using standard procedures was flavoured with 0%, 5%, 10% and 15% Julie mango pulp and labeled SC (Control), F1, F2, and F3 respectively. The results from the analysis with a significant difference (p<0.05) showed that the pH of the soya bean yoghurt ranged from 3.40 to 3.50. The scores obtained for sensory attributes (colour, smell, taste, sourness and flavor) of the Julie mango pulp flavoured soya bean yoghurt were compared with that of the plain soya bean yoghurt sample. The sensory evaluation result showed a mean score of 5.00 as overall acceptability for sample F3 for all sensory attributes (colour, smell, taste, sourness and flavor) thereby making it the most preferred sample by the panelists. Sample F2 had an overall acceptability mean score of 4.20 for all sensory attributes making it second in overall preference. Sample F1 has an overall acceptability mean score of 4.00, while Sample SC was the least preferred with an overall acceptability mean score of 2.80.
... Bulgaricus, by breaking down the sugar compound lactose into glucose and galactose under anaerobic conditions [1,2]. When the starter culture produces sufficient lactic acid, the lactic acid lowers the pH, making it tart (a characteristic sour flavour), causing the coagulation or thickening of the milk protein [3] This action acts as a preservative inhibiting the growth of pathogenic bacteria as they cannot grow in acid environment as well as maintains the yoghurt quality during storage and packaging [4]. The partial digestion of the milk when these bacteria ferment milk makes yoghurt easily digestible and helps those consumers with lactose intolerance [5] The use of fruit in yoghurt improves the Aesthetic value of the product (making it more pleasing) and delicious, retaining the health benefits of yoghurt and the refreshing flavour of the fruits [6,7]. ...
... To improve certain nutrients of yoghurt, flavours and fruit flavours are added to yoghurt during the production process to modify/improve the therapeutic and organoleptic properties. Presently, only flavoured yoghurts from fruits such as raspberry, banana, peach, vanilla, and strawberry are commercially available [4] However, some of these highly rated fruits could be replaced with some underutilized ones such as; Julie mango which was adjudged to be the consumer's choice from the varieties of mango owing to its nutritional profile, great taste, aroma and sensory acceptability [8,9] Furthermore, most Nigerian fruits like Julie mango are seasonal and due to poor storage condition, handling, disease, deterioration most of them are unfortunately wasted or lost either to spoilage or pests. Processing these fruits will reduce post-harvest losses and spread their availability throughout the year [8] To avoid these postharvest losses, these fruits (like Julie mango) could be formulated with yoghurt as flavouring agent as well as to enhance diversification, domestication and spread the availability of Julie mango juice throughout the year. ...
... The ammonia distilled off was absorbed by 50 cm 3 boric acid with indicator (bromocrysol methyl red) and this was titrated with 0.01 M hydrochloric acid (HCl). The titre value of the end point at which the colour changed from green to pink was then taken [4,15]. ...
Article
Full-text available
Plain yoghurt, 5%, 10% and 15% flavoured yoghurt samples were analysed for their proximate compositions, physico-chemical compositions, vitamin and mineral contents. The protein, moisture, fat and ash contents of the yoghurt samples decreased with significance (p<0.05) difference as the addition of Julie mango fruit juice increased. The carbohydrate, total solids, total solids non-fat, titrable acidity, vitamin C, and Calcium contents increased with significance (p<0.05) difference as the addition of Julie mango fruit juice increased. The pH on the other hand increased with no significance (p<0.05) difference between the yoghurt samples. All the formulated yoghurt samples in this study met the standard requirement for yoghurt production, hence could be hitherto modified to suit customers/consumers appeal for industrial mass production.
... lactis etc. are also not uncommon in some countries (Mckinley, 2005). The use of these traditional cultures has some advantages that it can grow even at low pH and their growth is not affected by acidity (Aswal et al., 2012;Corrieu and Beal, 2016;Mbaeyi-Nwaoha et al., 2017). Our literature search showed that pH, titratable acidity, syneresis and sensory profiles of yoghurt samples from the Kingdom of Lesotho have not been reported previously. ...
... Additionally, the inhibitory effect of dietary phytic acid on calcium bioavailability would be reduced by the low (Adolfsson et al., 2004). The low pH value of yoghurts also inhibits the growth of pathogens present in the yoghurts (Mbaeyi-Nwaoha et al., 2017). ...
Article
A total of nine yoghurt samples purchased from the Kingdom of Lesotho were evaluated for their pH, titratable acidity, syneresis and sensory profiles following standard procedures. The pH, titratable acidity and syneresis of these nine samples were found to be in the range of 3.94-4.22, 0.69-1.81 and 1.76-35.15%, respectively. The sensory profiles such as appearance, texture, aroma, flavour, taste and overall acceptability of these nine samples were found to be in the range of 2.5-4.5, 2.2-3.3, 2.5-4.1, 1.7-4.0, 2.1-4.3 and 2.3- 3.9, respectively. The pH of all nine yoghurt samples was complying in accordance with FDA specifications. The percentages of titratable acidity of some yoghurt samples were complying in accordance with FDA specifications and some samples were not. On the other hand, some samples have remarkably high syneresis. Our study showed that the pH, titratable acidity, syneresis and sensory profiles of these yoghurt samples were significantly different (p<0.05). Sensory properties, particularly, flavour, taste and aroma of yoghurt samples are needed to be improved for a better consumer overall acceptability. To the best of our knowledge, this is the first report of this kind on yoghurt samples from the Kingdom of Lesotho.
... The red grape yoghurt treatments gained lower protein content compared with apricot yoghurt treatments because the red grape has less protein content than apricot. Similar results were reported by Roy et al. (2015), Mbaeyi-Nwaoha et al. (2017) and Desouky (2018). During cold storage, there were significantly increase in the protein content for all yoghurt treatments and controls to reach the highest value for C 2. The treatment T 2 gained the lowest protein value at the end of storage period (21 days). ...
... The yoghurt treatments enriched with fruit juices had significantly higher CHO percentages when fresh and during storage period compared with the controls (without fruit juices). The CHO content increased with increase in the concentration of fruit juices in the fruitflavoured drinkable yoghurt treatments because red grape and apricot contains more sugar than milk (Hossain et al., 2012, Hassanein et al., 2014, Matter et al., 2016and Mbaeyi-Nwaoha et al., 2017. ...
... lactis etc. are still used in some countries, [3]. One of the advantages of these traditional cultures is that they grow even at low pH and their growth is not affected by acidity [1,4,5]. The disaccharide lactose present in the milk is converted into lactic acid by fermentation by these starter cultures. ...
... Lactic acid lowers the pH value and the milk protein casein present in the milk is coagulated and yoghurt is produced. Additionally, the low pH value serves as a method of preservation since at low pH value, the growth of pathogenic bacteria will be inhibited [4,5]. ...
... The fat, protein and ash content of fruit yoghurt tended to significantly decrease, while the TS, carbohydrate content and titratable acidity increased upon addition of mango pulp in the product (Desai et al., 1994, Rakhi et al., 2013, Mbaeyi-Nwaoha et al., 2017. The acidity of fruit yoghurt tended to increase while its pH tended to decrease as the rate of addition of strawberry pulp (9.74 % TS, 0.51 % acidity) was raised from 7.0 to 10.0 % by weight in the product (Yousef et al., 2013). ...
... The overall acceptability score of plain yoghurt and fruit yoghurt containing 10.0 % mango juice did not differ from each other, whereas product containing 10% mango pulp had significantly lower overall acceptability score compared to plain yogurt. It was recommended to use up to 20.0 % and 30.0 % of mango pulp and mango juice respectively, to produce acceptable quality mango flavoured yogurt (Mbaeyi-Nwaoha et al., 2017). The sensory overall acceptability score reported for yogurt made utilizing 5.0 % of black carrot juice was 5.74 as against a score of 7.14 for cherry flavoured yogurt (Ayar and Gurlin 2014). ...
... AOAC method 947.05 was used for determination of titratable acidity (TA), 925.23 for total solids, 991.20 for proteins and 923.03 for ash of fermented milk [12]. The crude fibre of fermented milk samples was estimated as described by MbAEyi-NwAohA et al. [13]. ...
... Also, the crude protein of yoghurts in this study is in agreement with reported values 1.29-3.52% from other studies [25] and lower than 4.50% [15]. [26]. ...
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Yoghurt remains a fermented milk of choice globally but its desirability is limited by quality attributes and syneresis. In this study, the effect of using exopolysaccharide (EPS) producing starter cultures and EPS on the quality attribute of yoghurt produced from cow milk was examined. Two starter cultures of EPS-producing LAB were used singly and in combination in three treatments portions (YEPS La, Lactobacillus acidophilus yoghurt; YEPS Ls, Leuconostoc suionicum; YEPS La + YEPS Ls, Lactobacillus acidophilus and Leuconostoc suionicum); Yxg, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus to produced yoghurt while reference Original Research Article Adamu-Governor et al.; AFSJ, 19(2): 28-39, 2020; Article no.AFSJ.62768 29 yoghurt (RY) was obtained from the market and refrigerated stored at 4 o C. Sensory, proximate composition, textural, rheological properties and whey separation were carried out after 1 and 28 days only, while physicochemical and microbiological were analyzed after 1, 7, 14 and 28 days. No significant difference (p ˂0.05) between RY (8.60 ± 0.60), (7.21±0.10) and YEPS La + YEPS Ls (8.54 ± 0.71), (7.25 ± 0.21) in overall acceptability for day 1 and 28. Moisture (82.45 ± 0.12-81.31 ± 0.06%), fat (3.46 ± 0.01-3.42 ± 0.03%) and carbohydrate (13.05 ± 0.11 to 12.51 ± 0.10%) contents decreased while total solids (17.57 ± 0.12-17.97 ± 0.12%), ash (0.56 ± 0.02-0.57 ± 0.02%) and protein (3.74 ± 0.01-4.30%) contents increased respectively across the yoghurts. The result showed that the highest cohesiveness and syneresis was observed in YEPS La + YEPS Ls (27.52 ± 0.63) and commercial yoghurt (29.10 ± 0.31), the lowest in Yxg (16.71 ± 0.21) and YEPS La + YEPS Ls (21.50 ± 0.51). The highest viscosity was observed in YEPS La + YEPS Ls across the rotation speeds. The pH and titratable acid ranged (4.28-4.50; 0.90-1.41) while the total bacteria colony count (5.5×10 8-11.0×10 8 cfu/ml) during 28 days storage period. Overall, EPS produced by EPS-producing LAB both In-vitro and In-vivo improve texture, mouthfeel, viscosity and reduce syneresis in yoghurt. Combine cultures of Lactobacillus acidophilus and Leuconostoc suionicum and their EPSs competed favourably with conventional starter, and other stabilizing agents in cow milk yoghurt.
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The growing demand for healthy yoghurt products necessitates the need to investigate the effect of process parameters and soursop puree to sugar concentration on the kinetic acidification, quality composition and sensory attributes of yoghurt. Taguchi design was used to interact incubation temperature (39–43 °C), pasteurization temperature (80–100 °C) and soursop puree to sugar ratio (0%, 50% and 75%) to produce nine yoghurt samples. The acidification kinetics of the yoghurt samples were estimated using maximum acidification rate, time required to achieve maximum acidification and time at which pH of 4.6 was reached. The proximate composition, mineral content (potassium, calcium and phosphorus), vitamin C, total phenolic content were the quality composition that were determined while the sensory attributes of the yoghurt samples were also evaluated. The maximum acidification rate, time required to achieve maximum acidification and time at which pH of 4.6 was reached were 0.0042 pH/min, 2 h and 3.5 h, respectively. This occurred when 75% of soursop puree to sugar ratio was used to produce yoghurt. The moisture content of the yoghurt samples decreases as the soursop to sugar ratio increases. The crude protein, crude fat, carbohydrate, fibre, vitamin C and total phenolic contents increases as the soursop to sugar ratio increases. The calcium content of the yoghurt samples ranges from 298.5 to 623.5 mg/l, 408.5 to 810.5 mg/l in potassium and 120–519 mg/l in phosphorous, respectively. This information could assist yoghurt producers to develop new yoghurt varieties with improved quality and sensory profile.
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19 Streptococcus thermophilus with high exopolysaccharide production were isolated from traditional Chinese fermented dairy products. The exopolysaccharide and viscosity of milk fermented by these 19 isolates were assayed. The strains of Streptococcus thermophilus zlw TM11 were selected because its fermented milk had the highest exopolysaccharide content (380 mg/L) and viscosity (7716 mpa/s). Then Streptococcus thermophilus zlw TM11 was combined with Lactobacillus delbrueckii subsp. bulgaricus 3 4.5 and the combination was named SH-1. The quality of the yogurt fermented by SH-1 and two commercial starter cultures (YO-MIX 465, YF-L711) were compared. It was shown that the exopolysaccharide content of yogurt fermented by SH-1 was similar to that of yogurt fermented by YF-L711 and significantly higher than YO-MIX 465 ( p < 0.05 ). In addition, the yogurt fermented by SH-1 had the lowest syneresis (8.5%) and better texture and sensory than the samples fermented by YO-MIX 465 and YF-L711. It manifested that the selected higher exopolysaccharide production starter SH-1 could be used as yogurt starter and reduce the amount of adding stabilizer, which can compare with the imported commercial starter culture.
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Goat milk is known to have better qualities such as digestibility and longer shelf life when processed than cow milk. Despite these qualities, goats are kept mainly for meat in many countries. The promotion of the full use of goat milk at household level to achieve cheap balanced diet and food/nutrition security is yet to be exploited. This paper discusses the possible differences between goats and cow milk, the importance and usefulness of processed goats milk and products for food/nutrition security in the household.
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With the specific objective of investigating the sensory concept of creaminess, as well as other sensory attributes obtained from descriptive analysis, a set of 25 samples of stirred low-fat yogurt were submitted to rheological (shear and imperfect squeeze flow viscometry, dynamic oscillation and Posthumus funnel) and sensory testing. Fat levels ranged from 0.3 to 3.5% and protein from 3.4 to 6.0%, and four different protein sources were employed, one being skimmed milk powder, the remaining three were milk protein preparations, one of which contained partially microparticulated whey protein (MPP). Based on averaged data from the sensory panel (n = 12), creaminess could be modeled by two other sensory descriptors, oral viscosity and smoothness (R2 = 0.78), but was poorly modeled by the entire set of rheological data. The MPP-containing blend did best in terms of matching the creaminess scores of a control yogurt containing 3.5% fat (no additional protein added).
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Physicochemical and nutrient evaluations of African bush mango seeds and pulp were conducted. The seeds contained 3.36%, 7.70%, 65.46%, 2.26%, 10.23% and 10.93% of moisture, crude protein, crude fat, mineral ash, crude fiber and carbohydrate, respectively. The pulp contained 80.0%, 1.09% , 1.06%, 0.8%, 0.4% 10.7% of moisture, crude protein, crude fat, mineral ash, crude fiber and carbohydrate, respectively. The physicochemical analysis of the pulp showed that it contained 0.112 cm3 titratable acidity, 0.21% water soluble ash, 459.7 mg/100 ml reducing sugars, 49.1% non-reducing sugars, 10.0 (Brix ) soluble solids, 1.3355 refractive index, 10.0% total solids, 1.2 103 NSM–2 viscosity and 1.012 specific gravity. Ascorbic acid and calcium contents were 66.7 mg/100 ml and 262.5 mg/100 g, respectively. The pulp was slightly acidic (pH 5.8) which indicates that it may not be easily spoiled by micro-organisms.