CHANGES IN MILK ON HEATING - VISCOSITY MEASUREMENTS

Skim milk was heated at 85-degrees-C for different holding times. As a result of such heating, whey proteins, in particular beta-lactoglobul in, denatured and associated with casein micelles. This led to an incr ease in size of the casein micelles but also to a different interactio n between them. Both these changes could be described by using a quant itative model which was developed for the viscosity of so-called adhes ive hard spheres. We applied the model successfully to skim milk and w ere able to describe on a quantitative basis the changes due to the he at treatment of milk. It was shown that after heating the casein micel les became larger and acquired a mutual attraction. The unfolding of t he whey proteins and their subsequent association with the casein mice lles appeared to be responsible for these changes. How this reaction i nfluences the fouling of heat exchangers is discussed.