Fabrication of whey proteins aggregates by controlled heat treatment and pH: Factors affecting aggregate size

Protein aggregates can be formed by heating globular proteins above the thermal denaturation of the proteins. These aggregates can be used as delivery systems or to modulate the physicochemical and sensory properties of food products. In this study, the effects of heat treatment (15 min at 80 °C), pH adjustment (between 4 and 9), aging at different temperatures (between 10 and 60 °C) and the rate of acidification (pH decreased from 6.25 to 4 at 5 different rates) on whey proteins aggregates were studied. The results indicated that these treatments led to creation of aggregates with different sizes (0.72-5.1 μm). Heat treatment and reducing the pH down to nearly 4 led to an increase in the size of aggregates. At pH < 7, by increasing the aging temperature, the size of aggregates increased (without heat treatment). In the heat treated samples with pH < 9, increasing the aging temperature led to an increase in the size of aggregates. Also larger aggregates were formed by increasing acidification rate. The amount of insoluble whey proteins aggregates increased as a result of applying heat treatment, decreasing pH and increasing aging temperature. The results of this study can be used for fabrication of whey proteins aggregates with specific size and functionality.