A comparative in vitro study of the digestibility of heat- and high pressure-induced gels prepared from industrial milk whey proteins

We undertook this study to compare the digestibility of heat- and high pressure-induced gels produced from whey protein isolate (WPI). To simulate in vivo gastrointestinal digestion of WPI gels, a pepsin–trypsin digestion system was used. The in vitro protein digestibility of WPI gels induced by high pressure (400 MPa and 30 min; P-gel) and those induced by heat (80°C and 30 min; H-gel) was compared using a protein concentration of 0.14 g mL^?1. The in vitro protein digestibility of P-gels was significantly greater than that of H-gels (p<0.05). The size-exclusion chromatography profiles of the hydrolysates showed that the P-gel generated more and smaller peptides than natural WPI and H-gels. Furthermore, Sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis showed some soluble disulfide-mediated aggregation in the P-gel, while there was more insoluble aggregation in the H-gel than the P-gel. The P-gel was more sensitive to proteinase than the H-gel, which was related to the content of S–S bonds, and this in turn could be attributed to the differences in the gelation mechanism between the H-gel and P-gel.