3.1.1. Extraction yield
It can be seen that the variable with the largest effect on extraction yield was linear term of incubator temperature (X1 followed by linear term extraction time (X2), quadratic term of extraction time (X22), linear term of pH (X3), quadratic term of temperature (X21) and quadratic term of pH (X23) (Table 3). However, the interactionterms (X1X2;X1X3 and X2X3) were found insignificant (p > 0.005). These results shown in Table 3 suggested that the change of extraction temperature, time and pH had significant effects (p < 0.005) on the yield of AIPS however there is no significant (p > 0.005) interaction effect between these parameters on the yield. The coefficient of determination (R2) of the predicted models
in this response was 0.9427. This would give a good fit to the mathematic
model in Eq. (5).