Rheology of buffalo milk rennet coagulation and gels affected by coagulation temperature, CaCl2, pH and milk heat treatment

Abstract

The effects of coagulation temperature, CaCl2 concentrations, pH and heat treatment on the rennet coagulation time (RCT), setting time (ST), aggregation rate (AR) and gel firmness (GF) of buffalo milk were studied using dynamic small amplitude oscillatory rheology. The influence of heat treatments on protein profile and casein micelle size was analysed by PAGE electrophoresis and dynamic light scattering. Reducing pH of milk from 6.5 to 6.3 caused the largest decrease in RCT and ST, and the largest increase in AR and GF (P < 0.01) compared with the influence of other examined factors. Decreasing the coagulation temperature from 31 to 27 °C had a minor effect on the rennet coagulation parameters. The amount of CaCl2 added to milk treated with mild heat treatment had a negligible effect on the rennet coagulation parameters. High heat treatment induced an increase in casein micelle diameter and substantially delayed the process of milk coagulation.