2.2.3. Orthogonal test
Owing to the degradation effect being the highest under optimum conditions, it was very important for enzymatic degradation to look for these optimum parameters.
However, study of the effect of changing single factor on enzymatic degradation was not enough to judge what parameter was optimum because other factors were fixed under this condition.
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.