Effect of pH on heat-induced casein-whey protein interactions: A comparison between caprine milk and bovine milk

Skim caprine and bovine milk, adjusted to pH 6.5–7.1 were heated at 90 °C for 10 min. The distribution of caseins, α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) between micellar and serum phases of both types of milk were determined. Depending on milk pH, the involvement of κ-casein (κ-CN) ranged from ∼8 to 52% and from ∼65 to 70% of total κ-CN in bovine and caprine milk, respectively. αS2-Casein and β-casein were only a part of micelle-bound complexes at all pH values in caprine milk. Denatured bovine β-LG and α-LA were involved in both soluble and micelle-bound heat-induced protein complexes. Conversely, denatured caprine β-LG was mainly associated with casein micelles (98–86% at pH 6.5–7.1) and was found in soluble complexes at higher pH (6–12% at pH 6.9–7.1). All denatured caprine α-LA was micelle-bound at all pH values. This knowledge could be very useful for understanding, controlling and modification of technological–functional properties of caprine milk.