So the optimum parameters should be obtained by using orthogonal test design. Reference to the design theory of orthogonal test, four controllable variables, hydrolysis time (A), hydrolysis temperature (B), pH (C) and enzymatic concentration (D), were selected for optimization.
Three levels of each factor were investigated.
The selected factors and levels were given in Table 1. The viscosity of the degradation products was measured under the above-mentioned factors and levels, and a further orthogonal analysis was carried out.