Cold-disaggregation of the Casein Micelles in Heated Concentrated Whey Protein-free Milk

Abstract

The amount of the soluble casein formed by cooling was much larger in the concentrated whey protein-free milk (WPF milk) heated at 135_??_140°C for 15 sec than in the unheated one. In the case of the heated concentrated WPF milk, the amount of soluble casein increased remarkably during the first 1 hr of cooling and gradually thereafter, while in the case of the unheated one the equilibrium between soluble and micellar casein was established after 1 hr of cooling. The temperature-dependent conversion of micellar casein to soluble casein was reversible in both the heated and the unheated concentrated WPF milk. The soluble casein formed by cooling bound a small amount of calcium. The κ- and α_s-casein contents of the soluble casein formed by cooling the heated concentrated WPF milk were somewhat higher than those of the soluble casein formed by cooling the unheated one.
It is considered from the above results that the structure of casein micelles is loosened by heat treatment of concentrated milk.