The effects of ageing of raw milk were investigated by following the a
ctual Ca2+-activity and physico-chemical properties of casein micelles
, namely, the average particle size, surface hydrophobicity, and renne
ting properties as well as the release of glycosylated and non-glycosy
lated caseinomacropeptide. Skimmed raw milk was stored at 4 degrees C
for 1 week in the absence and presence of various antimicrobial agents
. Proteinase inhibitors' efficiently prevented destabilisation and mol
ecular dissociation of casein micelles by indigenous and bacterial enz
ymes. The non-enzymic ageing of micelles must also be taken into accou
nt. It is characterized by a limited incorporation of ionic calcium in
to the micelle followed by an increase in pH-value, micellar voluminos
ity and particle size along with a decrease in the overall surface hyd
rophobicity of the casein micelles. Enzymic ageing affected the functi
onal role of micellar kappa-casein in the primary phase of renneting,
whereas the non-enzymic process did not affect the release of CMP duri
ng 1 week of storage.