Thermal stability of whey proteins studied by differential scanning calorimetry

The thermal stability of the bovine whey proteins.; β-lactoglobulin (β-1g), α-lactalbumin (α-1a) and serum albumin (BSA) was studied individually and in mixtures in the temperature range 25–140°C by differential scanning calorimetry. The thermal denaturation temperature (T_D) and the transition enthalpies (ΔH_app) were determined at different pH-values (3.0–10.0) in simulated milk ultrafil-trate (SMUF).β-Lg was, except at pH 9.0 and 10.0, the most thermostable protein at all pH-values. At acidic pH-values BSA was the least thermostable. At alkaline pH-values, however, α-la had lower thermal stability than BSA. α-La exhibited double peak behaviour at acidic pH-values and ΔH_app was dependent on Ca-content. Mixtures of the proteins were studied at pH 4.0, 5.0 and 6.6. In general, when mixed, the proteins seemed to denaturate independently of each other.