Effect of the native fat globule size on foaming properties and foam structure of milk

Abstract

In this study, effect of the native fat globule (NFG) size on the foaming properties of milk was evaluated. In order vary the size of NFGs in milk (0.8, 2.6, 3.7, 4.7 and 5.5 μm), separating cones of a commercial cream separator were modified, and combination of various fractionation and separation stages was utilized. All milk samples were standardized to 3.5% fat content (w/w). Results showed that the surface tension of the milk samples was independent of the NFG size, while viscosity and absolute zeta-potential values increased with an increase in the NFG size. Foamability of the milk samples only improved when the size of NFG was less than 2.6 μm. Average size of the air bubbles in foam increased with an increase in the NFG size, but the foam stability was not affected by the NFG size. A comparison with the homogenised milk samples of similar fat globule sizes suggested that the fat globule size controlled foamability while the alterations in the fat globule membrane composition governed the foam stability.