Control of the proteolytic reaction and of the level of bitterness in protein hydrolysis processes

Abstract

A generally acknowledged problem encountered in the use of enzymic hydrolysis for modification of food proteins is the formation of bitter taste. The bitter taste can be ascribed to hydrophobic peptides and results from the degradation of the protein substrate. The control of the level of bitterness is therefore to a large extent dependent on the control of the proteolytic reaction itself. Two methods for monitoring the proteolytic reaction are described: the pH‐stat technique and osmometry. Both methods give a quantitative expression for the degree of hydrolysis (DH) which is the percentage of peptide bonds cleaved. A low bitterness can usually be ascertained by restricting DH to low values (e.g. DH 3–5%). However, in certain protein hydrolysis processes which involve separation of the insoluble material, the reaction is continued to higher DH‐values. A reduced bitterness can then be obtained by iso‐electric precipitation of bitter peptides.