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Vol. 9(3) pp. 163-169, March, 2015
DOI: 10.5897/AJFS2014.1244
Article Number: 1B4E15150843
ISSN 1996-0794
Copyright © 2015
Author(s) retain the copyright of this article
http://www.academicjournals.org/AJFS
African Journal of Food Science
Full Length Research Paper
Production and quality evaluation of flavoured yoghurts
using carrot, pineapple, and spiced yoghurts using
ginger and pepper fruit
Ihemeje, A., Nwachukwu, C. N. and Ekwe, C.C.*
Department of Food Science and Technology, Faculty of Agriculture and Veterinary Medicine, Imo State University,
Owerri, Nigeria.
Received 29 November 2014; Accepted 10 February 2015
Production and quality evaluation of plain yoghurt, spiced yoghurt (pepper fruit, ginger) and flavoured
yoghurt (carrot and pineapple) were carried out being proximate composition, mineral analysis,
microbiological analysis, organoleptic evaluation and statistical analysis. Results show significant
(p<0.05) nutritional enhancement of the plain yoghurt by the addition of spices and flavourings. The
mineral content of the plain yoghurt were likewise increased. Organoleptically, the spiced and flavoured
yoghurts were all acceptable by consumers but pepper fruit spiced yoghurt was the most preferred in
terms of general acceptability.
Key words: Yoghurt, pepper fruit, carrot and pineapple.
INTRODUCTION
Yoghurt is a fermented dairy product obtained from the
lactic acid fermentation of milk. It is one of the most
popular fermented milk products in the world (Willey et
al., 2008).
Bourlioux and Pochart (1988) defined yoghurt as a
coagulated milk product that results from the fermentation
of lactose in milk by Lactobacillus bulgaricus and
Streptococcus thermophilus. Other lactic acid bacteria
(LAB) are also frequently used to produce yoghurt with a
unique characteristic (Adolfsson et al., 2004). It is a
nutritionally beneficial product generally considered safe,
with taste liked by many people.
Yoghurt is produced commercially by pasteurising the
milk mixture, cooling to 45C before being inoculated with
known cultures of microorganisms referred to as starter
culture. The starter culture may be mixed Lactobacillus
bulgaricus and Streptococcus thermophilus in a ratio of
1:1. They act on lactose and result in the production of
lactic acid which increases the acidity of the yoghurt,
thereby forming gel.
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 (Saint et al., 2006).
Yoghurt can boost immunity. The regular consumption
of live cultured yoghurt produces a higher level of
immunity boosting interferon as this bacteria cultures
stimulate infection-fighting white cells in the blood stream
with anti tumor effects (Maltock, 2007). Yoghurt is
nutritionally rich in protein, carbohydrate, vitamins and
minerals (for example calcium) which contributes to a
*Corresponding author. E-mail: chibyzaps@gmail.com. Tel:+2348037351535, +2348152886345.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0
International License
164 Afr. J. Food Sci.
healthy living including decreasing the risk of colon
cancer, improved digestion and many other benefits
(Gray, 2007).
Sensory appeal is one of the essential strategies
associated with the market success of fermented
products like yoghurt. The popularity of yoghurt as a food
component has been linked to its sensory characteristics
(Routray and Mishra, 2011). Furthermore, there is need
to introduce other fruit and vegetable flavours like carrots,
pineapple and spices such as ginger and pepper fruit so
as to produce yoghurt with spicy taste with a charac-
teristic aroma and fragrance. Also, to improve the
nutritional composition of yoghurt produced.
Health benefits of yoghurt
Lactobacillus, a probiotic (friendly) bacteria found in
yoghurt offers remarkable preventive and curative effects
on arthritis (Gray, 2007). Yoghurt is easier to digest than
milk and so many people including children who cannot
tolerate milk, either because of a protein allergy or
lactose intolerance can enjoy yoghurt more digestible
than milk. Bacterial enzymes created by the culturing
process partly digest the milk protein casein making it
easier to absorb and less allergenic (Witton, 2004).
Yoghurt contains intestine friendly bacteria culture
(lactobacteria) that fosters a healthy colon and lowers the
risk of colon cancer by promoting the growth of healthy
bacteria and thereby deactivate harmful substances
which can cause problem in the colon (Gray, 2007). It is
also rich in calcium which contributes colon health and
decreases the risk of colon cancer (Gray, 2007).
The regular consumption of live cultured yoghurt
produces a higher level of immunity boosting interferon
as these bacteria cultures stimulate infection fighting
white cells in the blood stream with anti tumor effects
(Maltock, 2007). Daily consumption of ounces (100 g) of
yoghurt significantly improved the cholesterol while
raising high density lipoprotein (HDL) (good cholesterol).
This may be because of the ability of the live culture in
yoghurt to assimilate cholesterol or because yoghurt
binds the bile acids which lowers cholesterol (Maltock,
2007).
Carrot (Daucus carita)
Carrot (Daucus carita) is a root vegetable, horn like in
shape, usually orange in colour, though purple, red,
white, and yellowed varieties exist. It has a crisp texture
when fresh.
The most commonly eaten part of the carrot is taproot,
although the green are sometimes eaten as well. It is a
domesticated form of the wild carrot D. carota, native to
Europe and South Western Asia. The domestic carrot
has been selectively bred for its greatly enlarged and
more palatable, less woody textured edible taproot.
Carrots are widely used in many cuisines, especially in
the preparation of salads, and carrot salads are
traditional in many regional cuisines (Mabey, 1997; Rose,
2006).
Pineapple (Ananas comosus)
A. comosus is a tropical plant in the Bromeliaceae family.
This delicious fruit is full of nutrients that promote good
health. Raw pineapple are loaded with vitamins, enzymes
and minerals including vitamin A, vitamin C, calcium,
phosphorus, manganese and potassium, which are
important to health, it is also rich in fibre and calories and
low in fat and cholesterol (Marcela, 2012). Both the root
and fruit may be eaten or applied topically as an anti-
inflammatory. The anti-inflammatory properties can
greatly alleviate the pain of arthritis (Marcela, 2012).
Pepper fruit (Dennettia tripetala)
Pepper fruit (D. tripetala) is a well-known forest fruit and
indigenous spicy medicinal plant. It is a tropical rain forest
plant widely domesticated in the Southern, Eastern and
Western parts of Nigeria (Chandraseharen, 1994). It can
be chewed in different forms. Okafor (1980) reported that
pepper fruit (D. tripetala) contains minerals and vitamins.
Pepper fruit is a spice medicinal plant for curing fever,
cough, toothache, as well as stimulant and is used in the
preparation of some special dishes for pregnant and
postpartum women, during which it is claimed that the
spices and herbs aid in uterine contraction (Oyemitan et
al., 2006).
Ginger (Zingiber officinale)
Ginger (Z. officinale) is consumed as a delicacy,
medicine or spice. Ginger produces a hot, fragrant
kitchen spice. Young ginger rhizomes are juicy and fleshy
with a very mild taste. They are often pickled in vinegar or
sherry as a snack or just cooked as an ingredient in many
dishes. They can also be steeped in boiling water to
make ginger tea. Ginger is generally prized for its use as
a herb, flavour and as a spice, not as a nutritional
supplement. According to Catherine (2010), 2 g of ginger
contains only 1.6 calories, 0.7 mg of omega-3 fatty acids
and 2.4 mg of omega-6 fatty acids. It provides 0.1 mg of
vitamin C and 0.2 mg of folate. Ginger also contains
minute amounts of minerals: calcium (0.3 mg),
magnesium (0.9 mg), phosphorus (0.l7 mg), potassium
(8.3 mg) and sodium (0.3 mg).
This work will introduce new varieties of flavoured and
spiced yoghurt from carrot (D. carita, pineapple (A.
comosus), pepper fruit (D. tripetala) and ginger (Z. officinale),
which will be of good nutritional quality and health
benefits. This work will also reveal and get people
informed of the nutritional significance and additional
usefulness of these fruits and spices; thus increasing
their importance to mankind.
The objectives of this research included production of
flavoured and spiced yoghurt using ginger, pepper fruit,
carrot and pineapple; evaluation of nutritional quality and
the flavoured and spiced yoghurts; determination of
microbial load of the flavoured and spiced yoghurt and
determination of organoleptic qualities of the flavoured
and spiced yoghurts.
Ingredients for yogurt production
Milk
Milk is the major product in the production of yogurt
(Lopez, 1997). The type of milk used depends on the
type of yogurt: whole cream milk for full fat yogurt, low fat
milk for low fat yogurt. Milk in yogurt a rich flavour and
smooth texture, contribute to energy and forms cream
formation with water.
Starter culture
The main starter culture used in yogurt production is
Streptococcus thermophilus and Lactobacillus bulgaricus.
They can grow independently but the rate of acid
production is much higher when used together than when
used individually.
S. thermophilus grows faster and produces both acid
and carbon dioxide. The production of carbon dioxide
stimulates the growth of L. bulgaricus. On the other hand,
the proteolytic activity of L. bulgaricus produces
stimulatory peptides and amino acids used by S.
thermophilus. These micro-organisms are ultimately
responsible for the formation of typical yogurt flavour and
texture. The yogurt mixture coagulates during fermen-
tation due to drop in pH. The streptococci are responsible
for the initial pH drop of the yogurt mix to approximately
5.0. The Lactobacilli are responsible for the further
decrease of pH to 4.5.
Gelatin
Gelatin is a protein produced by partial hydrolysis of
collagen extracted from boiled bones, connective tissues,
organs and some intestines of animals such as
domesticated cattle, pigs, and horses. It is used as a
stabilizer to increase the firmness and viscosity of yogurt.
Tamime and Robinson (1999) reported that gelatin has
the ability to bind water, reacts with the milk constituents
(mainly proteins), and stabilize the protein network
preventing free movement of water. Gelatin tends to
degrade during process at high temperature.
Ihemeje et al. 165
Consequently, the yoghurt gel is considered weakened.
Gelatin is used at a level of 0.3-0.5% to get a smooth
shiny appearance and should be geared to the
consistency standard for yoghurt. Alais and Linden
(1999), disclosed that gelatin has a wide spread uses in
foods without any limits imposed.
Water
Water plays an important role in yogurt making. The
quantity of water must be carefully controlled such that
the milk and the bacteria have correct available amount
of water to make a yogurt of proper consistency.
Water provides the following functions in the making of
yogurt: It creates an enabling environment for multipli-
cation; it helps in the homogenization and forms the
medium for enzyme activation and it helps to control
yogurt temperature.
MATERIALS AND METHODS
Collection of samples
Skimmed powdered milk, carrot, pineapple, pepper fruit, ginger,
gelatin, yoghurt culture and granulated sugar produced by Dangote
Sugar Company were obtained from Eke-Ukwu Market in Owerri
municipal council of Imo State, Nigeria.
The practical work which involved the production of flavoured and
spiced yoghurt was conducted in the Food Processing Laboratory
of the Department of Food Science and Technology, Imo State
University, Owerri, Imo State. The laboratory analysis of the yoghurt
samples was carried out at National Root Crop and Research
Institute, Umudike in Abia State.
Sample processing
The samples of yoghurt were produced according to International
Standard of yoghurt as described by Guler and Mutlu (2005). Here
400 g of skimmed powder milk was reconstituted with water and
heated to 80C for 15 min for pasteurization, and then allowed to
cool to 42-45C before inoculation with starter culture. The milk
mixture was divided into five portions, raw yoghurt, carrot flavoured
(sample C), pineapple flavoured (sample B), pepper fruit spiced
(sample D), ginger spiced (sample E). They were incubated at 43C
for 10-12 h (overnight) until a pH of about 4.3-4.5 was attained. The
analyzed.
Proximate analysis
The total solid of the yoghurt sample was determined using
gravimetric method described by AOAC (1999).
The moisture and ash content of the yoghurt samples was
determined using the indirect method employing drying oven and
furnace incineration method described by Onwuka (2005). The
protein content of the sample was determined by the semi-micro
Kjeldahl, method reported by AOAC (1990).
The fat content of the sample was determined on wet weight
basis by Soxhlet’s method as described by Suzanne (2003). The
carbohydrate content of the sample was determined by estimation
using the arithmetic difference method described by James (1995).
166 Afr. J. Food Sci.
Mineral determination
The resulting ash was dissolved in 100 ml of dilute hydrochloric
acid (HCL) and then diluted to 100 ml in volumetric flask using
distilled water. The digest so obtained was used for the mineral
analysis.
Phosphorus in the sample was determined by the vanado-
mohybdate (yellow) spectrometry described by James (1995).
Calcium and magnesium contents of the test samples was
determined by the ethylenediamine tetraacetic acid (EDTA)
complexiometric titration of AOAC (1990).
Potassium content of the sample was determined by flame
photometry. The instrument was set up according to the
manufacturer’s instruction. The equipment was switched on and
allowed to stay for about 10 min. The gas and air lets were opened
and the start knob was turned on AOAC (1990).
Microbiological analysis of samples
Determination of microbial load (coliform, bacteria and fungi
load)
The method of the international commission on microbiological
specification for foods ICMSF (1978) was adopted and used.
Total viable microbial count
A suspension of the bacteria was serially diluted and aliquots of
each dilution was placed in suitable culture media (Hausler, 2003).
Organoleptic evaluation
The product samples were evaluated using hedonic method for
sensory characteristics and overall acceptability by a panel of 40
judges selected randomly. They were served coded samples of
yoghurt and asked to compare it by testing for taste, aroma, texture,
appearance, and overall acceptability. All tests were performed and
rated on a 9-point hedonic scale described by Ihekoronye and
Ngoddy (1985) : like extremely, 9; like very much, 8; like
moderately, 7; like; slightly, 6; neither like or dislike, 5; dislike
slightly, 4; dislike moderately, 3; dislike very much, 2; dislike
extremely, 1.
Statistical analysis
The data obtained from sensory evaluation was analysed using
analysis of variance (ANOVA), according to the method of Iwe
(2002) to determine the variance ratio. Sample means were
compared to determine treatment effects. The least significant
difference was calculated at 95% level of significance using tukey
test (T-test), (Ihekoronye and Ngoddy, 1985).
RESULTS AND DISCUSSION
Proximate composition of plain
Yoghurt
The proximate composition of plain yoghurt (neither
flavoured nor spiced) shows protein (9.97%), moisture
(84.67%), fat (1.80%), Ash (0.44%), and carbohydrate
Table 1. Nutritional
composition of plain yoghurt
(PY).
Parameter
Plain yoghurt
CHO
1.70
Protein
9.97
Fat
1.8
Ash
0.44
Fibre
0.32
Moisture
84.67
Table 2. Vitamin (mg) of yoghurt samples
composition.
Vitamins
PY
PFY
GFY
CFY
PFY
Vitamins A
5.87
6.05
5.86
6.66
5.92
Vitamins C
3.90
4.01
3.91
4.25
4.48
Riboflavin
o.52
0.53
0.53
1.00
0.89
Thiamine
1.86
2.57
1.86
3.90
1.92
Niacin
2.01
2.02
2.01
2.02
2.25
(1.70%) contain (Table 1).
The high moisture content of the product could be as a
result of the dilution (reconstitution) of the milk prior to
fermentation. The low fat content of the yoghurt could be
attributed to the low oil content of the milk (Skimmed
milk) which was the major substrate of the yoghurt
produced.
This corresponds with the work of Amna et al. (2008)
that non-fat (zero%) yoghurt can be produced but in
general, the fat level of every yoghurt depends on oil
content of the milk, whether skimmed or full cream milk.
He stated categorically that yoghurt manufactured from
skimmed milk will likely have very low fat content (within
the range of 1-2%) while those produced from full cream
milk will have fat content in the region of 4% (or slightly
above).
Also the ash and fibre content were remarkably low and
this result agrees with observation of Cheeseman and
Lean (2000) that generally, yoghurts have poor fibre level
because they are milk and water based products.
Carbohydrate (lactose) is the major constituents of milk
that is converted to lactic acid during yoghurt (fermen-
tation) production task of the yoghurt. So the fermentation
and conversion of lactose to lactic acid accounts for the
low content of carbohydrate of yoghurt as observed in the
result (Table 2).This corroborates with the works of Mistry
and Hassan (1992) and Younus et al. (2002)
The observed protein content (9.97) of the plain
yoghurt compares favourably with commercial standard
stated by National yoghurt Association (2000), that
commercial yoghurt should have 11-18% protein. Also,
Adolfsson et al. (2004) reported protein content (1003)
which is in agreement with the result in Table 1.
Ihemeje et al. 167
Table 3. Mineral analysis of yoghurt samples.
Parameter
PY (mg/g)
PFSY ( mg/g)
GSY mg/g
C FY mg/g
PFY mg/g
Calcium
180
180.05
180.00
180.00
180.00
Phosphorus
158
158.12
158.33
158.04
158.10
Magnesium
170
170.08
170.001
170.14
170.00
Sodium
111
111.06
111.10
111.07
111.10
Potassium
121
121.50
121.02
121.11
121.12
Iron
108
110
108
108.1
108.1
Mineral analysis of raw plain, flavoured and spiced
yoghurts
Mineral analysis of plain yoghurt (mg/g) revealed calcium
(180), phosphorus (158), magnesium (170), sodium (111)
and potassium (121) content. The result justifies the
ascertion of Gray (2007) that yoghurt is a very good
source of essential minerals needed for human
metabolism or functionality of cells. Addition of pepper
fruit and carrot respectively caused slight increase in
calcium, phosphorus, magnesium, sodium and potassium
(0.5, 0.11). A similar increase in minerals was also
observed by Ihemeje et al. (2013) where pepper fruit was
used in Zobo drink production.
D. tripetala (seed) has earlier been reported to contain
minerals, vitamins, and oils (Okafor, 1980), protein, fibre,
ash, and carbohydrate (Udoessian and Ifon, 1984; Okwu
et al., (2004). Carrot according to Cohen et al. (2010) is
rich in calcium, magnesium and potassium. This may
have caused the observed increase in mineral value of
the products. Carrot is well known for its B- carotene
content (a precursor of vitamin A) and fruits containing B
carotene can be used in the management of
vibroacaustic disease (VAD) in adults especially in poor
resource countries (Novotry et al., 1995)
The iron content was only remarkably improved in
sample B (pepper fruit flavoured). This further justifies
that pepper fruit contains appreciable quantity of iron as
earlier reported by Ihemeje et al. (2013)
Ginger and pineapple respectively caused varied
increase phosphorus (0.03,).11), sodium (0.1,0.1) and
potassium (0.02, 0.12). Ginger is known for its pungent
and stimulant effects and contains more oleoresins than
minerals (Connell, 1970; Nwinuka et al., 2005). It has
more of Cherepeutic effects than nutritional. On the other
hand, pineapple contains more vitamins and minerals
than ginger. (Nutrient data pineapple, 2012) especially
water soluble Vitamins (Vit. C.) This explains why higher
value of minerals was observed in pineapple favoured
yoghurt than ginger spiced yoghurt.
Vitamin contents of plain flavoured and spiced
yoghurt
The vitamin contents of plain flavoured and spiced yoghurts
Table 4. pH value of the yoghurt
samples.
Yoghurt sample
pH
Plain
4.6
Pepper fruit spiced
4.7
Ginger spiced
4.7
Carrot flavoured
4.7
Pineapple flavoured
4.5
Value are means of triplicate
determination.
is shown in Table 4. The plain yoghurt contained vitamin
A (5.87 mg), vitamin C (3.90 mg) riboflavin (0.52 mg),
thiamine (1.86 mg), niacin (2.01). Addition of pepper fruit,
carrot and pineapple respectively caused improvement in
vitamin A (0.18, 0.79 and 0.05), vitamin C (0.11, 0.35 and
0.58), riboflavin (0.01, 0.48 and 0.37), thiamin (0.71, 2.04
and 0.06) and niacin (0.01, 0.01 and 0.24) contents
above that the observed increased in the vitamin
contents could be a justification of the report that carrot
(Cohen et al., 2002) pepper fruit (Ihemeje et al., 2013)
and pineapple(Hale et al; 2010) are all rich in vitamin
.similar trend of increase in vitamin content of flavoured
and spiced yoghurts was respec-tively recorded by Amna
et al. (2008) and Mbaeyi and Anyanwu(2010)
The pH of the various yoghurt sample are presented in
Table 3 result indicates that pineapple flavoured by the
plain yoghurt (4.6) pepper fruit spiced yoghurt, ginger
spiced yoghurt and carrot flavoured yoghurt had the
same pH (4.7). Addition of pineapple as a flavourant
caused the pH to drop from 4.6 to 4.5. This could be
attributed to two reasons; the pineapple juice contains
appreciable quantity of ascorbic acid, also it was not
diluted with water.
Unlike ginger, carrot and pepper fruit that were
extracted with water before adding them into the yoghurt.
A corresponding alteration of pH of plain yoghurt was
observed by Gabriel et al. (2013) in their work on the
production of probiotic yoghurt flavoured with the spice
Aframomum danielli, strawbeing and vanilla. The result
also corroborates earlier research by Mbaeyi and
Anyanwu (2010) on production and evaluation of yoghurt
flavoured with solar dried bush mango.
168 Afr. J. Food Sci.
Table 5. Microbial count of plain, flavoured and spiced yoghurt.
Simple
Dilution factor
Total bacterial count (cfu/ml)
Total coliform (MPN/100 ml)
PLY
102
0.8×103
0
PFSY
102
1.0×103
1
GSY
102
0.9×103
0
CFY
102
1.4×103
1
PFY
102
1.3×103
1
PLY, plain yoghurt; PFSY, pepper fruit spiced yoghurt; GSY, ginger spiced yoghurt; CFY, carrot
flavoured yoghurt; PFY, pineapple flavoured yoghurt.
Microbiological assessment of plain yoghurt
Coliform group of bacteria
The Table 5 shows the results obtained after microbial
examination of the samples. There was no evidence of
coliform in samples PLY and GSY while PFSY, CFY and
PFY had some evidence of coliform after production.
That could be because of the extraction of pineapple,
pepper fruit, ginger and carrot during processing.
Turkish standard institute, (1989), state that a
maximum count of 10 cfu/ml of coliform group bacteria
was allowed in yoghurt. So, the samples with values less
than 10 cfu/ml are therefore justified suitable and safe for
consumption. But absence of coliform will help extend the
shelf-life of the products.
Different studies showed higher yoghurt counts of the
coliform group bacteria in yoghurt samples. Dun and
Ozgunes (1981) reported that 30 cfu/ml of coliform group
bacteria was found in the yoghurts sold commercially in
Ankara, Turkey.
Total bacteria count
The total bacterial count of the microbiological analysis
showed sample PFY had (0.8X103) PFSY had (1.0X103)
GSY had (0.9X103) CFYhad (1.4103) PFY had (1.3X103).
There was no much difference in the total bacterial
count in the spiced and flavoured yoghurts.
Micro- organisms used as starter culture have contributed
to the yoghurt total bacterial count of the yoghurt
samples.
Also the source (farm to market) of flavourants
(pineapple and carrot) and spice (pepper fruit and ginger)
may have contributed to the total bacterial count which is
above that of plain yoghurts.
The bacterial count levels are very much within or
below the acceptable range (8.7cfu) according to
National Yoghurt Association (NYA, 2006).
Conclusion
From the results obtained, the nutritional quality of the
plain yoghurt was improved by the addition of pepper
fruit, ginger, carrot and pineapple especially in terms of
vitamins and minerals. This implies that the therapeutic
potency of yoghurt could be improved because
consumption of foods with high vitamins A and C can aid
in combating deficiency diseases like scurvy and night
blindness. Adequate supply of minerals improve
functionality of cells and also supports immunity of the
body. The sensory attributes (colour, texture, aroma,
taste, general acceptability) evaluated revealed
appreciable degrees of acceptance by consumers
thereby increasing varieties of yoghurts, in the market.
This also justifies additional economic importance /use of
pepper fruit, ginger, carrot and pineapple. Pepper fruit
spiced yoghurt was most preferred in terms of general
acceptability.
Recommendation
It is recommended that information on the production of
spiced and flavoured yoghurts using pepper fruit, ginger,
carrot and pineapple should be disseminated to domestic
and commercial manufacturers of yoghurts and also it
very necessary that further work should be done where
pepper fruit, ginger, carrot and pineapple may be
incorporated in yoghurt formulation before fermentation
rather than being added as mere flavourants or spices.
This research if carried out would reveal nutritional
implication and organoleptic attributes of such products.
Conflict of interests
The authors did not declare any conflict of interest.
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