Abstract: The procedure of the enzymatic hydrolysis of proteins from tilapia head by flavourzymeTM protease was studied through three consecutive experiments. The effects of four factors including starting pH,temperature,water-head ratio and enzyme-substrate ratio on α-amino nitrogen (α-AN) contented in tilapia head protein hydrolysate (THPH) were evaluated by 24 orthogonal test,the result showed that E: S ratio and temperature have great influence on α-AN. Optimal conditions of E: S ratio,hydrolyzing time,starting pH and temperature for this hydrolysis procedure were established as 20LAPU/g,3h,6.5～7. 0 and 50～55℃,respectively. Linear relationships were found between lg (E: S ratio) and α-AN at a period of hydrolyzing time of 0.5,1,2,3 and 6h,with correlation coefficients of R2=0.9804,0.9890,0.9708,0.9887 and 0.9311,respectively.

Key words:  , enzymatic hydrolysis； tilapia head； &alpha, -amino nitrogen； optimization； flavourzymeTM；