PROTEASE-CATALYZED CONDENSATION OF PEPTIDES AS A POTENTIAL MEANS TO REDUCE THE BITTER TASTE OF HYDROPHOBIC PEPTIDES FOUND IN PROTEIN HYDROLYSATES

Synthetic dipeptides of varying hydrophobicity were used as a model sy stem to investigate the feasibility of reversed protease action as a m eans of improving the flavor of bitter peptides found in protein hydro lysates. The four different proteases tested were able to convert hydr ophobic dipeptides into an insoluble precipitate, but with different e fficiencies. Hydrophilic dipeptides did not give detectable condensati on or precipitation. Solid-state and solution NMR were used to monitor peptide bond formation in C-13-labelled peptides. NMR and MS analyses showed that the products consisted of higher oligomers of the origina l peptide. Bitterness decreased in the order starting with dipeptides > whole reaction mixtures >> isolated precipitates. Taste improvement correlated with peptide bond formation and the formation of insoluble material. These observations indicated that the condensation reaction was driven by precipitation of insoluble reaction products and that th is process is a potential means to improve the flavor of bitter peptid es extracted from protein hydrolysates. (C) 1998 Elsevier Science Inc.