Emulsifying properties of protein fractions prepared from heated milk

Abstract

Heated milk was separated into κ-casein/whey protein-rich and κ-casein-depleted fractions using centrifugation. The emulsifying properties of the two fractions were compared to those of sodium caseinate, whey protein isolate and casein micelles. Fat surface areas, which formed on emulsification at different power inputs, were essentially similar for both fractions and also for casein micelles, but were considerably lower than those for sodium caseinate and whey protein isolate. Protein load (mg protein/m2 fat surface area) decreased with increasing fat surface area and followed the order: casein micelles > κ-casein-depleted micelles ≈ whey protein/κ-casein-rich fraction > sodium caseinate > whey protein isolate. Emulsions stabilized by either fraction and by casein micelles were more stable at low fat surface areas than those stabilized by sodium caseinate or whey protein isolate. Emulsification capacities of the two fractions were lower than those of the other three proteins. It appeared that the size of the protein aggregates is more important than their composition in determining the emulsifying properties. © 1993.