In vitro dynamic gastric digestion of soya protein/milk protein blended beverages: influence of protein composition and co-processing.

The gastric digestion behaviours of blended protein beverages containing different ratios of casein, whey protein and soya protein that were heat-treated at 60 °C or 80 °C were investigated using an in vitro dynamic human gastric simulator. All beverages showed protein aggregation and curd formation under gastric conditions; the extent of protein aggregation/curd formation was dependent on the protein composition of the beverage. The beverages with high proportions of milk proteins showed a greater degree of curd formation during gastric digestion, due to the coagulation of casein micelles. These beverages also showed a lower rate of protein emptying from the stomach. Increasing the relative proportion of soya protein in the beverage increased the rate of protein emptying, because of changes in the curd structure caused by the interactions of soya protein with casein micelles. There was a relatively small effect of heating to 80 °C on the protein emptying rate and the protein content of the clot. The results suggest that protein beverages with different protein compositions could be developed to provide controlled delivery of proteins and amino acids.