Ultrasonic analysis of heat-induced coagulation in calcium fortified milk

Abstract

The key components determining the physical behaviour of milk are casein micelles. Heat-induced coagulation of casein micelles is a major problem in the design of new milk-based products in the food industry. Many of food additives reduce the stability of casein micelles in milk, leading to coagulation during heat treatment. Up to now there was a lack of experimental methods allowing fast, non-expensive and technically non-complicated analysis of the heat stability of milk colloids. In the present work we used a new high-resolution ultrasonic resonator technique to monitor the coagulation of calcium fortified low fat milks. The technique provides a relatively cheap, rapid and non-destructive analysis and requires small volumes of material. Two independent parameters, ultrasonic velocity and ultrasonic attenuation in milk, were measured as a function of temperature to analyse the effects of the addition of calcium and selected stabilisers on the coagulation temperature. Both parameters give the same value of coagulation temperature with a resolution better than 0.1 K. The results allowed us to evaluate the concentrations of stabilisers required to prevent the coagulation of calcium fortified milk at temperatures below 373.15 K. © Springer-Verlag 1999.