Functional properties of fish protein hydrolysate from herring (Clupea harengus)

Raw herring (Clupea harengus), a waste product from the roe industry, was hydrolyzed, using an endopeptidase preparation from Bacillus licheniformis. Aliquots were taken at 0, 5, 10, 20, 30, 45, and 60 min hydrolysis to measure the degree of hydrolysis. The functional properties tested were emulsifying activity index (EAI), foamability, and foam stability of the hydrolysate. At 36% hydrolysis, the herring hydrolysate presented good emulsifying stability (>120 minutes) and an adequate foam expansion (142%), as compared to the soluble fraction from the unhydrolyzed control herring. The lipid content decreased considerably to 0.77% for the fish protein hydrolysate, while its protein content increased to 77%, The amino acid composition remained similar to that of the control.