Factors affecting molecular characteristics of whey protein gelation

Abstract The effects of pH, protein concentration, NaCl, heating temperature and time on the gelation of a whey protein concentrate (WPC) and the associated changes in the molecular conformation of the individual whey proteins were studied using polyacrylamide gel electrophoresis, high performance liquid chromatography and Fourier transform infrared spectroscopy. Heat denaturation was studied using differential scanning calorimetry. The results obtained showed that varying WPC concentration affected textural properties of gels without any observed differences in the molecular behavior of α-lactalbumin and β-lactoglobulin, while heating temperature, pH and NaCl affected both molecular and textural characteristics. WPC formed firm gels at temperatures above 70 °C, at alkaline pH range and in the absence of NaCl. When the whey proteins were heated, α-lactalbumin did not aggregate above pH 7 but denatured readily to form aggregates at acid pH while β-lactoglobulin aggregated at both acid and alkaline pH regions. Denaturation of α-lactalbumin at neutral pH resulted in an increase in viscosity while denaturation of β-lactoglobulin resulted in gel formation. The aggregation of WPC, particularly at alkaline pH, was attributed mainly to β-lactoglobulin and only minimally to α-lactalbumin.