## 3 Results and Discussion
### Effect of Input Parameters on Free Gossypol Reduction (FGR)  
The gossypol reduction in cottonseed meal is affected by several parameters such as used solvents, temperature, time, solvent ratio, etc. [8]. In the present study, the effect of various parameters viz. acetone %, time of extraction, LSR, and the number of extraction cycles on FGR percentage were analyzed using response surface methodology. The 3D surface plot for two varying parameters, namely time and acetone %, and their combined effect on FGR have shown in Figure 5a. The graph depicts that at the lower level of time (30 min) and 70% acetone, the FGR value was found about 86%, whereas, at a higher  
Figure 4: Comparison between measured and predicted values for TGR. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Source** & **Free Gossypol (F\({}_{\text{g}}\))** & **Total Gossypol (T\({}_{\text{g}}\))** \\ \hline  & Prob. \(>\) F & Prob. \(>\) F \\ Model & \(<\)0.0001 & \(<\)0.0001 \\ A-Acetone \% & 0.002 & \(<\)0.0001 \\ B-Time in Min & 0.0462 & 0.0009 \\ C-Liquid-to-Solid ratio & \(<\)0.0001 & \(<\)0.0001 \\ D-No. of Extraction & \(<\)0.0001 & \(<\)0.0001 \\ AB & 0.9334 & 0.1987 \\ AC & 0.1214 & 0.1128 \\ AD & 0.2423 & 0.0793 \\ BC & 0.8893 & 0.1244 \\ BD & 0.1472 & 0.9003 \\ CD & \(<\)0.0001 & 0.0020 \\ A\({}^{2}\) & \(<\)0.0001 & \(<\)0.0001 \\ B\({}^{2}\) & 0.0213 & 0.0226 \\ C\({}^{2}\) & 0.0765 & 0.113 \\ D\({}^{2}\) & 0.5072 & 0.7319 \\ Lack of Fit & 0.0695 & 0.0754 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Model summary statistics for free gossypol and total gossypol reduction. level of time (60 min) and acetone (90%), there was only a slight improvement observed in FGR. In this 3D effect plot, the time has not shown much effect on FGR, whereas the maximum FGR percentage was observed at the middle level of acetone. The results are in agreement with a previous study of a similar kind carried out by [35]. Figure 5b presents the combined effect of LSR and acetone % on FGR, keeping the other two parameters (time and number of extraction cycles) constant. It showed that the FGR percentage increases with an increase in LSR and acetone levels. The reason behind this may be that a large amount of fresh solvent would be available for the extraction and scrubbing of the solute by the solvent [8]. A maximum FGR percentage was observed at a higher level of LSR and middle level of acetone. Figure 6a depicts the combined effect of the number of extraction cycles and acetone (%) on FGR percentage. The results showed that there is a slight improvement in the FGR percentage by increasing the no. of extraction cycles at a constant level of acetone. The maximum reduction of free gossypol was found at the middle level of acetone percentage and a higher level of no. of extraction cycles. Figure 6b shows the combined effect of LSR and time of extraction on FGR percentage while the other two parameters (acetone % and no. of extraction cycles) were kept constant. In this case, the time has a negligible effect on FGR at a constant level of LSR, whereas the LSR has a significant influence on FGR at any time. It was observed that at a lower level of LSR and time, FGR is also less, whereas the maximum reduction in free gossypol was recorded at a higher level of LSR (10) and time (60 min). The reason being the more acetone will be available for mixing the gossypol in it. Figure 5: (a) 3D surface plot between time of extraction and acetone (b) 3D surface plot between LSR and acetone. Figure 6: (a) 3D surface plot between no. of extraction cycles and acetone % (b) 3D surface plot between LSR and time of extraction. The combined effect of the number of extraction cycles and time on FGR percentage has been shown in Figure 7a. In this case, acetone % and LSR were kept constant at the middle level. The results showed that the number of extraction cycles has a great effect on FGR at any time. In contrast, maximum FGR percentage was observed at a higher level of time (60 min) and more number of extraction cycles (4). Figure 7b illustrates the combined effect of no.