3.3.3 Response Surface Plots
In this study, process parameters were optimized through response surface quadratic model (RSQM), and contour plots in form of 2D and 3D were used to describe the model. These plots show the interactions between two variables in the optimized phase thereby providing several solutions by the combination of parameters that could yield the best optimum results for this type of enzymatic hydrolysis of PFAD process. Figures 3.3 to 3.5 are the pictorial representations of two-factor interactions describing the RSQM. Here, the gridded contour plots were generated to interpret the response variable (total tocopherols) in a rectangular coordinate system. The plots show a 3-D surface in 2-D with contour lines delineating changes in the 3-D space. The contour lines represent lines of equal response value and the profile was visualized as response contours of two-factors at a time scenario. The remaining predictors contributing least to the response are fixed at a given point. For instance, in Fig. 3.3, lipase weight and water weight were fixed at one base to extract result from the prediction profiler. Similarly, Figures 3.4 and 3.5 were depicted in the same manner.
In Figures 3.6 to 3.8, the gridded surface plots are representations of the surface plots in actual 3-D space. The response surface model with the incorporation of the second order effects of non-linear relationship was the optimisation technique to determine the yield of tocopherols during the enzymatic hydrolysis of PFAD, therefore the plots determined the optimum operating conditions reaching maximum from the best-fitted model with a map of contour lines, followed a direction of movement along the path of maximum response.