Protein hydrolysates from Pacific whiting solid wastes

Alcalase and Neutrase showed optimum activity against Pacific whiting solid wastes (PWSW) at pH 9.5, 60 degrees C and pH 7.0, 55 degrees C, respectively. Alcalase had a higher proteolytic activity than Neutrase. Enzyme concentration, reaction time, and waste/buffer ratio significantly affected the hydrolysis and nitrogen recovery (NR)(p < 0.05). Optimum conditions for PWSW hydrolysis were 20 AU Alcalase/kg, 1 h reaction time, waste/buffer ratio of 1:1 (w/v). Correlation between the degree of hydrolysis (DH) and NR (R-2 = 0.970-0.978) was high. Freeze-dried hydrolysate was brownish yellow in color (L* = 54.59, a* = 6.70, b* = 27.89) and contained 2.77% moisture, 79.97% protein, 13.44% ash, and 3.83% lipid. Amino acid composition of freeze-dried hydrolysate was similar to that of PWSW and Pacific whiting muscle but tryptophan was reduced to 21.50% and 14.74%, respectively.