High-pressure treated mixed gels of gelatin and whey proteins

Abstract

Microstructural and rheological properties of high-pressure treated mixed and pure gels of gelatin and whey protein concentrate (WPC) were studied at pH 7.5 and 5.4. The microstructure was studied using light microscopy and transmission electron microscopy, and the rheological properties using dynamic oscillatory measurements and tensile tests. The results showed that the high-pressure treatment induced a higher degree of aggregation for the pure WPC gels, compared with a conventional heat-treatment, showing a network that consisted of larger aggregates and pores, leading to a weaker gel strength. The pure gelatin networks were unaffected by the high-pressure treatment. Differences in rheological properties were, however, found between pressurized and unpressurized gelatin gels. At pH 5.4, the high-pressure treated mixed gels formed a phase-separated network with a gelatin continuous phase and a discontinuous WPC phase. The rheological properties of the mixed gels followed those of pure gelatin independently of the WPC concentration. At pH 7.5, the rheological properties of the high-pressure treated mixed gels indicated a higher degree of gelatin continuity compared with the heat-treated mixed gels. The microstructural studies showed a dense network in which neither the gelatin nor the WPC network could be identified.