HIGH-PRESSURE TREATED MIXED GELS OF GELATIN AND WHEY PROTEINS

Microstructural and rheological properties of high-pressure treated mi xed and pure gels of gelatin and whey protein concentrate (WPC) were s tudied at pH 7.5 and 5.4. The microstructure was studied using light m icroscopy and transmission electron microscopy, and the rheological pr operties using dynamic oscillatory measurements and tensile tests. The results showed that the high-pressure treatment induced a higher degr ee of aggregation for the pure WPC gels, compared with a conventional heat-treatment, showing a network that consisted of larger aggregates and pores, lending to a weaker gel strength. The pure gelatin networks were unaffected by the high-pressure treatment. Differences in rheolo gical properties were, however, found between pressurized and unpressu rized gelatin gels. At pH 5.4, the high-pressure treated mixed gels fo rmed a phase-separated network with a gelatin continuous phase and a d iscontinuous WPC phase The rheological properties of the mixed gels fo llowed those of pure gelatin independently of the WPC concentration. A t pH 7.5, the rheological properties of the high-pressure treated mixe d gels indicated a higher degree of gelatin continuity compared with t he heat-treated mixed gels. The microstructural studies showed a dense network in which neither the gelatin nor the WPC network could be ide ntified.