THERMAL-DENATURATION OF WHEY PROTEINS IN MIXTURES WITH CASEINS STUDIED BY DIFFERENTIAL SCANNING CALORIMETRY

Thermal unfolding of whey proteins and whey protein-casein mixtures in simulated milk ultrafiltrate was studied by differential scanning calorimetry. The results are reported as transition enthalpy, temperature of peak maximum, and van’t Hoff enthalpy related to the sharpness of transition. The results of earlier investigations were reviewed. It is suggested that a large part of reported whey protein unfolding data are affected by subsequent aggregation reactions. Pure caseins showed no endotherms on heating. In mixtures of whey proteins and individual caseins, β-casein showed no effect. Addition of 5% α-casein to 5% whey protein lowered the denaturation temperature of all whey proteins by 2 to 3°C. κ-Casein did not affect the denaturation behavior of bovine serum albumin and α-lactalbumin, but it lowered the denaturation temperature of β-lactoglobulin by 3°C. In the pH range from 6.4 to 7, where the whey protein casein interaction is known to change drastically in highly heated milk, no abrupt changes are seen in thermal unfolding of β-lactoglobulin, either alone or in mixture with κ-casein. © 1990, American Dairy Science Association. All rights reserved.