Control of competing destabilizing mechanisms in the formation of milk gels: Pectin-induced phase separation and rennet aggregation

This research studied the effect of high methoxyl pectin (HMP) and kappa-carrageenan on casein micelles stability and on their aggregation induced by rennet. Different HMP concentrations were added to skim milk, to cause different extents of phase separation, and casein micelles aggregation was then induced by the addition of rennet. The presence of HMP affects the kinetics of destabilization of the casein micelles and at high HMP concentrations the formation of a gel network is inhibited, due to depletion effects. The extent of visible phase separation can be reduced by addition of 0.015% kappa-carrageenan. These results demonstrate that it is possible to control the aggregation of casein micelles by modulating the extent of phase separation induced by the polysaccharides in milk. In situ studies using DWS and ultrasonic spectroscopy make fine-tuning of phase separation and aggregation possible.