Abstract: Enzymatic hydrolysis parameters of casein were optimized with orthogonal design and uniform design methods respectively. The results showed that the highest hydrolysis degree of casein under the optimized conditions with orthogonal design is higher than that with uniform design,they are determined as 79.27% and 59.81%,respectively with trichloro acetic acid(TCA) precipitation method and the corresponding parameters including casein concentration,enzyme to casein ratio,temperature,pH and time are 6% and 4%,4% and 4%,58℃ and 56℃,8.0 and 8.0,3 h and 2.33 h,respectively. The highest hydrolysis degree of casein under the optimized conditions with orthogonal design is colse to that with uniform design as 10.82% and 10.73%,respectively. Which were determined with formaldehyde titration method and the corresponding parameters including casein concentration,enzyme to casein ratio,temperature,pH and time are 8% and 10%,6% and 7%,56 ℃and 58 ℃,7.5 and 8.0,3 h and 3 h,respectively. Therefore,the optimization result of orthogonal design is better than that of uniform design method when the numbers of experimental factor and level are few.

Key words: orthogonal design, uniform design, casein, enzyme, hydrolysis