Rennet Coagulation of Milk Retentates. 1. Effect of Thermal and Mechanical Stresses Associated with Ultrafiltration

Effects of UF on clotting kinetics, curd hardening, and whey syneresis of raw and pasteurized milk were studied. Milk was subjected to thermal and mechanical stresses similar to those occurring in a UF plant. To isolate the effects of milk recirculation from those due to protein concentration, a UF batch loop system similar to an industrial system was used. Recirculation was obtained returning both retentate and permeate to the feed tank. Mechanical and thermal stresses associated with UF treatment caused a slight reduction of curd hardness and a decrease in whey separation rate. These effects, however, were less marked than those induced by pasteurization or by an increase in protein concentration, both of which are associated with practical UF of milk.