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.