Studies on the impact of glycation on the denaturation of whey proteins

It could be shown for technologically relevant whey protein powders that denaturation of beta-lactoglobulin (beta-Lg) is affected significantly by the extent of covalent modification of lysine residues by lactose. The amount of acid soluble beta-Lg as measured via RP-HPLC with UV detection after heating for 10 min at 80 A degrees C increased from 40% (4.6% lysine modification) to 82% (22.4% lysine modification). An increase in glycation leads to a slower denaturation-induced oligomerisation, as shown by SDS-PAGE. Concomitant with an increase in lysine modification, the denaturation temperature increased from 79.5 to 84 A degrees C, as measured by differential scanning calorimetry (DSC). Covalent attachment of lactose to whey proteins during preparation or storage significantly improves the heat stability of whey proteins, which may be of particular importance for the technological use of whey proteins varying in the degree of lysine modification.