[Effect of Maillard protein modification on protein resistance to hydrolysis by digestive proteinases]

A study was made of the influence of the Maillard reaction in proteins on their digestibility by pepsin, trypsin, and chymotrypsin. The model substrates were obtained by heating bovine serum albumin (BSA) and beta-lactoglobulin (BLG) with glucose for the preset period of time at 50 degree C. The rate of proteolysis by alkaline proteolytic enzymes was measured by the autotitration technique, whereas pepsin activity was determined by fluorometry. An evidence was obtained that digestibility by trypsin and chymotrypsin of BLG-glycose decreased, while the amount of protein bound carbohydrate increased. In the case of BSA, the incubation with glucose led at first to an insignificant lowering of digestibility by these two enzymes whereupon the protein resistance decreased. Thermal processing of both BLG and BSA in the absence of glucose led to a distinct growth of digestibility as compared to the native forms of proteins. As to pepsin, the authors failed to find any decrease in the digestibility of the Maillard compounds. It was revealed that the Maillard reaction in proteins had different effects on digestibility of different protein substrates by different proteolytic enzymes.