The results obtained in the present study suggest a gelation
mechanism that is similar to acid gelation, with the difference that
proteolysis instead of acid causes a destabilisation of the casein
micelle. Acidification of milk leads to a reduced repulsion of casein
micelles due to a reduced negative charge of -casein, followed by a
rearrangement of the casein micelles by solubilisation of calcium
due to the pH drop that leads to the formation of a gel network
(Lucey & Singh, 2003). While the gelation by plasmin depends
mainly on the rate of hydrolysis, the gel properties of acid gels
depend largely on the rate of acidification (Anema, 2008). Since the
pH inMilk72 is only decreasing slightly, the repulsion by -casein is
still present in Milk72 and inhibits aggregation of casein micelles,
which explains the absence of -casein in the gel network.
The results obtained in the present study suggest a gelationmechanism that is similar to acid gelation, with the difference thatproteolysis instead of acid causes a destabilisation of the caseinmicelle. Acidification of milk leads to a reduced repulsion of caseinmicelles due to a reduced negative charge of -casein, followed by arearrangement of the casein micelles by solubilisation of calciumdue to the pH drop that leads to the formation of a gel network(Lucey & Singh, 2003). While the gelation by plasmin dependsmainly on the rate of hydrolysis, the gel properties of acid gelsdepend largely on the rate of acidification (Anema, 2008). Since thepH inMilk72 is only decreasing slightly, the repulsion by -casein isstill present in Milk72 and inhibits aggregation of casein micelles,which explains the absence of -casein in the gel network.
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