Whey protein aggregation under shear conditions - effects of pH-value and removal of calcium
The effects of pH-value and a reduction in calcium content on the kinetics of whey protein denaturation and the aggregation behaviour, under shear in a scraped surface heat exchanger, were examined. The denaturation rate of β-lactoglobulin at 80 °C is considerably retarded as the pH-value decreases from pH 6.7 to 4.5. Aggregates which are produced under shear between pH 4 and 5.5 reveal a small particle size (<5 μm) irrespective of the lactose content and the heating temperature. This is attributed to the low reactivity of the thiol groups and the small net charge of the proteins in this pH-range. At a reduced calcium concentration the heat- and shear-treatment resulted in a gritty structure with large rubber-like particles. These are not to be taken as primary whey protein aggregates but as fragments of a fine-stranded gel.