Protein hydrolysates were prepared from Bombay duck (Harpodon nehereus) by the combination of commercially available papain and Flavourzyme (Novozymes, Copenhagen, Denmark) . The influences of hydrolysis time and enzymes substrate ratio on the degree of hydrolysis (DH) were investigated in detail. Hydrolysates were freeze-dried and the obtained powder was characterized with respect to yield, moisture, nitrogen recovery, amino acid composition and peptide molecular mass distribution. The mechanism of reducing bitterness of hydrolysates was also studied. A DH of up to 19.7% was obtained under the optimal hydrolysis conditions. The mass yield, nitrogen recovery and moisture of freeze-dried fish protein hydrolysates were 10.5 g/100 g wet weight of raw material, 87.5% and 4.2%, respectively. The molecular mass of hydrolysates determined by size-exclusion chromatography was between 219 and 5,245 Da. The oligopeptides were the main fraction of the hydrolysates. It was significant that L-leucine was removed from oligopeptides to reduce the bitterness of hydrolysates.


Bombay duck (Harpodon nehereus) has high a nutrition value, with a protein content of up to 70% of dry mass. There is a great interest in utilizing the proteins of this fish efficiently on industrial scale. The hydrolysates of the fish protein were prepared by enzymatic hydrolysis and dry-freezing. The characteristics of hydrolysates were determined to predict their potential as a nutritious supplement in various food products. Low molecular peptides were the main composition of the hydrolysates, which possess health properties and promote food products supplemented by hydrolysates as healthy and nutritious.