Hydrolysis of a chitosan-induced milk aggregate by pepsin, trypsin and pancreatic lipase

The addition of chitosan to whole milk results in dose dependent destabiliz ation and coagulation of the casein micelles and milk fat. The present stud y evaluates how the presence of chitosan could affect the hydrolysis of thi s chitosan-induced aggregate by different gastrointestinal proteases (pepsi n and trypsin) and by pancreatic lipase. The chitosan-milk aggregate was hy drolyzed by pepsin and trypsin, as evaluated by the UV absorbance of TCA-so luble peptides and by urea-PAGE. The kinetics and extent of hydrolysis were independent of the casein being soluble or aggregated. The release of solu ble peptides from the aggregate was independent of the presence of chitosan . A progressive inhibition of pancreatic lipase was observed in proportion to the increase in molecular weight of the chitosan employed to induce the fo rmation of the aggregate. Interestingly, the presence of chitosan not only affected the initial velocity of the reaction, but also reduced its extent. The results indicate that a milk aggregate induced by chitosan was very wel l digested by gastric and intestinal proteases independently of the molecul ar weight of the chitosan used, and that the aggregate could retain the lip id-lowering effect of chitosan.