Cheese proteolysis and matrix disintegration during in vitro digestion

The proteolytic changes under in vitro digestive conditions were examined by urea-polyacrylamide gel electrophoresis, Kjeldahl determination of nitrogen, and fluorescamine analysis to evaluate the level of free amino terminal groups as an indicator of the degree of proteolysis. The protein and fat components of cheese digesta were visualized by confocal laser scanning microscopy. Cheese disintegration and subsequent release of proteins and polypeptides was quantified after each of three in vitro digestion phases: oral, gastric (pepsin, pH 2), and intestinal (pancreatic enzymes, pH 6.8). Most of the disintegration of the cheese protein matrix (˜75%), proteolysis, and protein release occurred during the intestinal digestion phase. Fat aggregate release from the cheese matrix mostly occurred in the gastric and intestinal digestion phases, and globules became more spherical after the gastric phase. Proteolysis took place primarily in the gastric and intestinal phases. These results show the importance of microstructure and the digestive environment on the release of cheese components.