A comparison of native state of casein micelles of buffalo and cow milk and its molecular changes under different physico-chemical conditions
Résumé
Buffalo milk is the second most produced milk in the world after cow milk with about 13% (89.3
out of 693.7 billion litres) contribution in the world’s milk production. Buffalo milk increased at
a double rate as compared to cow’s during last decade at global level. 92% of this milk is
produced in India and Pakistan. This milk is majorly handled by “informal sector” in all its
producing countries except Italy.
Quantitatively, buffalo milk is richer in all major constituents like fat, lactose, minerals and
proteins particularly in casein contents than that of cow milk (casein concentration of buffalo
milk is equivalent to total protein concentration of cow milk). Caseins are present in the form of
supramolecular spherical colloidal structures named casein micelles like other milks. Casein
micelles play a key role in milk for its biological and technological functionalities. Despite of lot
of literature on casein micelles of cow milk, its micellar organization and dynamics are not well
known whereas the knowledge on casein micelles of buffalo milk is even far less especially in its
native state and under different physico-chemical conditions.
The objective of this study was to gain knowledge on casein micelles of buffalo milk in its native
state and its molecular changes as a function of different physico-chemical conditions (ionic
strength, acidification, alkalinisation, microfiltration/diafiltration and heat-treatments). The
comparison with casein micelles of cow milk was used as a reference throughout the study.
Biochemical, physic-chemical, molecular, microscopic, macroscopic, physical and organoleptic
approaches were used to compare casein micelles of both milks. The proportion of casein/soluble
proteins was 80/20 in both milks. In native state, casein micelles of buffalo milk were higher in
concentration, bigger in size, less hydrated, more mineralized as compared to casein micelles of
cow milk with similar charge and casein classes. The comparison of amino acids sequences of
casein micelles showed a homology of 95% in both milks which globally depicts the similar
molecular organization of caseins. Casein micelles showed similar behavior against different
physic-chemical conditions like cow milk qualitatively but due to quantitative differences, there
found some delays in molecular changes in the buffalo’s casein micelles.
It showed that buffalo milk can be employed for the production of products which are already
being produced by cow milk like different types of cheeses and to prepare casein constituents.
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