Abstract: The enzymatic hydrolysis of tilapia waste by flavourzyme combined with papain was optimized by combinedly using Plackett Burman (PB) design, steepest ascent design and central composite design. Firstly, PB design was applied to identify hydrolysis time and solid-to-liquid ratio as the most significant of 6 factors influencing the hydrolysis degree of tilapia waste. Then the center points of the two factors were determined based on steepest ascent design. Finally, the optimization of the two factors was carried out by using central composite design. The results showed that the optimal hydrolysis conditions were as follows: solid-to-liquid ratio 1:6.25, hydrolysis temperature 45 ℃, hydrolysis time 4 h, enzyme dosage 0.3% and the ratio of flavourzyme to papain 1:3. Under such conditions, the experimental degree of hydrolysis was 22.38%, which was in good agreement with the predicted one of 21.50%. In conclusion, the optimized process has good reliability.

Key words: tilapia, waste, Plackett-Burman design, central composite design, response surface analysis