Use of cold microfiltration to produce unique ?-casein enriched milk gels

Abstract

Bovine milk was modified using cold microfiltration to produce β-casein enriched fractions with unique gelation properties. Skim milk at 4 °C was microfiltered using membranes with pore diameter of 0.2 μm, 0.1 μm, or 100 000 g.mol -1 MWCO. Resulting permeates were filtered again using membranes with 10 000 g.mol -1 MWCO to create retentates with 9% solids that were used in the gelation study. Ash, calcium, lactose, solids, and protein contents of all fractions were monitored to determine separation trends. Cold microfiltration significantly reduced the casein:whey protein ratio and increased the β-casein:α s -casein ratio in the retentates from the second filtration; the smaller the pore size of the initial separation membrane, the greater the change in the ratios. When treated with glucono-δ-lactone and rennet, the β-casein enriched fractions produced using the 0.2 and 0.1 μm membranes formed softer gels that had greater syneresis and hydration, and lower water holding capacities than skim milk gels.