HEAT-TREATED WHEY-PROTEIN HYDROLYSATES - EMULSIFYING AND FOAMING PROPERTIES

Whey protein isolate was modified by proteolysis using a broad-spectru m protease in combination with heat treatment of the hydrolysate. The degree of hydrolysis and the adjustment of pH during heat treatment go verned the emulsifying and foaming properties of the modified protein. The emulsion resistance to coalescence increased when the hydrolysate was heated at pH 4.0 and 8.0, while the reverse trend was observed wh en heating pH was 6.0. Emulsions showed evidence of age thickening dur ing a 4-weeks storage period. However, the change in viscosity during storage decreased with increasing degree of hydrolysis. Emulsions sepa rated in four distinct phases upon storage. Modification of whey prote in isolate increased opacity at the bottom of the emulsion and reduced the thickness of the cream layer. Whipping properties (overrun, firmn ess and stability) of modified isolate substantially improved when the hydrolysate was heated at pH 8.0. When heating pH was 4.0 or 6.0, the effect on foaming properties were slight.