PHYSIOCHEMICAL PROPERTIES OF
YOGHURT MADE BY CULTURING
MILK FROM DIFFERENT DAIRY
PRODUCERS: BUFFALYPSO, GOAT
AND COW
*R. Maharaj and D. Singh-Ackbarali
University of Trinidad and Tobago, Caroni North Bank Road, Centeno,
Trinidad & Tobago, W. I.
E-mail: [email protected]
Tel.: 1 868 642 8888; Fax: 1 868 642 1617.
TRINIDAD & TOBAGO BACKGROUND
T&T with a population of 1.4 M people, lies to the south of the
West Indian archipelago, 11 km from the Venezuelan coast.
Economy is dependent on the oil & gas sector and lure of this sector
has led to the detriment of agriculture. GDP/Capita $16,843 US.
Agriculture contributes < 1% GDP, employs about 4% of labour
and food importation bill is in excess of 600 Million US, with local
production of about 8% of staple foods.
It is important to diversify the economy and increase food security
and provide sustainable and productive employment opportunities.
We must reduce our food import bill. “Simply, we must eat what
we grow and grow what we eat”.
INTRODUCTION
• Dairy industry, is one of the largest sectors in the food industry
(Silanikove et al., 2015). In Trinidad however, this sub-sector is
under-developed as production does not meet local demand.
• One considerable drawback to dairy-based food consumption is
increasing lactose intolerance among adult population.
• Low-lactose products eg. yoghurt allow some lactose intolerant
individuals to overcome this intolerance
• While studies on the physiochemical attributes of goat and cow milk
and their derived products exist, there is limited literature on
buffalypso milk and milk products.
• No data comparing the physiochemical properties of milk produced
from Trinidad buffalypso with diary cows and goats.
RESEARCH OBJECTIVES &
METHODOLOGY • This study investigated sources of milk: from crossbred holstein cow, saanen goat
and an alternate source of milk, buffalypso and evaluated and compared the
physiochemical properties of buffalypso, goat and cow milk before and after
inoculation with lactic acid bacteria.
• Collected milk was pasteurized using a water bath set at 72°C
• Internal temperature was maintained for 15 seconds and then flash cooled
These were separated into batches for analysis and yoghurt production
• Samples were stored in a refrigerator for subsequent processing and analysis. Milk for compositional analysis were preserved using potassium di-chromate or chloroform depending on method of analysis. All reagents used where analytical grade.
Streptococcus thermophilus & Lactobacillus bulgaricus
cultures for yoghurt production were food grade
• To every 1L of milk, 80g of sugar was dissolved and left in a water bath until the temperature stabilized to 42°C.
• 1.25g each of Streptococcus thermophiles & Lactobacillus bulgaricus was added and left in water bath incubator at 40°C for 24 hours
yoghurt samples were separated for physical analysis
and the samples for compositional analysis were
preserved by storing in air tight container in the refrigerator.
Physiochemical Analyses
All meters were cleaned calibrated before use and analyses were performed in triplicate.
For the titratable acidity the 0.1 N NaOH was previously standardised, and values were
expressed as lactic acid equivalents.
Parameter Instrument Name/AOAC Reference
Number
pH HANNA desktop pH meter, HI3220
Colour Hunterlab, ColorFlex EZ's 45°/0°
Viscosity Brookfield Engieering Viscometer and
Spindle HB5
Water activity, aw Aqualab water activity meter
Fat, solid-non-fat
(SNF), lactose & salt
Lactoscan SP milk analyser
Total nitrogen AOAC 991.20 method (19th ed. 2012)
Protein was calculated as N x 6.38.
Titratable acidity (TA) AOAC 947.05 method (19th ed. 2012)
Microbiological Analyses
• Skim milk agar was used to determine if there were any
undesirable microorganisms in the milk after
pasteurization.
• Dilutions of 1/10, 1/100 and 1/1000 were prepared with
¼ ringer solution.
• 1ml of each dilution for each source of milk was pipetted
aseptically into sterile petri plates to which 10ml of
cooled milk agar was added and mixed well.
• After solidification the plates were allowed to stand for
one hour before transferred to an incubator set at 35°C
for 2 days.
Statistical Analysis
• Means of 3 determinations were analyzed using
analysis of variance (ANOVA).
• Significant differences between means were
determined at P < 0.05.
RESULTS
* Values are means of 3 replicates (±standard deviation). Experimental values within columns that
do not have a common superscript are significantly different (p<0.05)
Physiochemcial analyses of buffalypso, goat and cow pasteurized milk & yogurt.
Sample
Fresh Milk Yoghurt
Parameter Buffalypso Goat Cow Buffalypso Goat Cow
Viscosity, cP (mPa*s)
n/a n/a n/a 440b 160c 640a
Colour L* a* (G-R) b* (B-Y)
89.37d, -4.14a, 3.56f
88.95d, -3.14b, 5.28d
86.2e, -3.3b, 3.9e
92.61a, -3.02b, 11.55a
91.84b, -2.94b, 9.46c
90.49c, -2.46c, 11.32b
aw 0.995a 0.993a 0.994a 0.996a 0.996a 0.996a
pH 7.3b 7.2b 7.8a 3.7c 3.6c 3.6c
TA 0.09b 0.22b 0.08b 1.68a 1.59a 1.53a
Protein, % 3.56c 3.16c 3.2c 6.78b 8.28a 6.70b
Fat, % 7.28a 4.04b 2.9c 8.88a 5.58b 3.40c
SNF, % 9.69c 8.60d 8.80d 18.52b 22.60a 18.08b
Lactose, % 5.32a 4.73b 4.84b 3.18d 3.88c 3.14d
Salt, % 0.79a 0.71a 0.72a 0.48a 0.58a 0.46a
RESULTS
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
Buffalypso Goat Cow
pH
an
d T
itra
tab
le A
cid
ity
pH pH Titratable Acidity Titratable Acidity
Figure - Changes in pH and titratable acidity of buffalypso, goat and cow milk after
culturing/yoghurt production.
RESULTS
• Preparation of yogurt slightly changed the levels of
protein, SNF and lactose, since the milk were all
pasteurized before culturing, the effect should not be due
to indigenous microflora on such constituents but
possibly, the activity of the lactic acid bacteria on the
different types of milk.
• The results of the milk agar plates (<1000 cfu/ml)
supported that indigenous microflora should not have
contributed to this and these would be as a result of the
lactic acid bacteria cultures added for yoghurt production.
CONCLUSIONS • Cow milk and yoghurt were the least white while buffalypso milk
and yoghurt were the most white.
• Cow milk had the highest pH and all milks had similar decrease
after culturing, the 3 yoghurts also had similar pH (P>0.05).
• Variation in nutrient content for the three different milks was
noticeable only for fat, this was highest for buffalypso (P<0.05).
Thus any one of the milk sources could be a substitute for the other
with respect to the nutrients derived from it.
• Composition of three yoghurt types was different when compared to
the fresh milk especially for protein, SNF and lactose (P<0.05).
• Viscosity was different for all yoghurts (P<0.05), highest for cow
and lowest for goat:-goat milk may be more suitable as a drinking
yoghurt.
LITERATURE CITED
• Bozanic, R., Tratnik, L., & Maric, O. (1998). The influence of goat milk on the viscosity and microbiological quality of yogurt during storage. Mljekarstvo, 48(2), 63–74.
• Güler, Z. (2007). Levels of 24 minerals in local goat milk, its strained yogurt and salted yogurt (tuzlu yo˘gurt). Small Ruminant Research, 71, 130–137.
• Lucey, J.A. (2016). Acid Coagulation of Milk. In Advances Dairy Chemistry, McSweeney P., O’Mahony J. (Eds). Springer, New York, NY.
• Silanikove, N., Leitner, G., & Merin, U. (2015). The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds. Nutrients, 7(9), 7312–7331. doi:10.3390/nu7095340
• Vargas, M., Chafer, M., Albors, A., Chiralt, A. & Gonzalez-Martinez, C. (2008). Physicochemical and sensory characteristics of yogurt produced from mixtures of cows’ and goats’ milk. International Dairy Journal, 18, 1146–1152
