The key aim for optimization was
The key aim for optimization was to obtain a highest possible extraction yield while consuming less H2O2. In the above investigation, it PSI was found that the effect of temperature was indeed decisive, thus the optimum points for Y1 and Y2 ( Figs. S1 and S2) were suggested at the highest temperature. The desirability function approach is one of the most widely used methods for optimization of multiple response processes ( Chu et al., 2012 and Mahjub et al., 2011). A constraint to maximizing the FeCl3 or Fe2(SO4)3-based extraction yield and minimizing H2O2 concentration was to set the goal to locate the optimum settings of independent variables using the Design-Expert 7.0 software based on the criterion of desirability. To get the desired optimum responses, variables were restricted to 1.0 ? A ? 3.0, 30 ? B ? 90 and 80 ? C ? 120, whereas the FeCl3-and Fe2(SO4)3-based extraction yield of responses were restricted to 10.33% ? Y1 ? 94.54%, and 23.753% ? encapsulation efficiency (Y2) ?70.812%. Importance varies from the least important (+) a value of 1, to the most important (+++++) a value of 5. At the same time, the ‘important’ for the FeCl3-based extraction yield was adjusted to 5, while the ‘importance’ for H2O2 concentration was set to 2 as windows default. By means of this method, there are 6 solutions to obtain high extraction yield with low H2O2 dosage. One of the optimal conditions obtained with desirability at 0.913 were 1.44% for H2O2 concentration, 90 min for reaction time and 120 °C for temperature with the predicted yield of 92.09% for Y1. Likewise, the ‘importance’ for the Fe2(SO4)3-based extraction yield and H2O2 concentration were adjusted to 5 and 2, resulting in 9 solutions. Among them, 92.89% of extraction yield was predicted with desirability of 0.922 at the optimal conditions of 1.30% for H2O2 concentration, 90 min for reaction time and 120 °C for temperature, showing similar tendency with FeCl3-based one. Interestingly, optimal conditions suggested from another solution were 1.00% for H2O2 concentration, 30.09 min for reaction time and 120 °C for temperature with predicted extraction yield of 86.80%. Therefore, from economic standpoint, sperm might be better option to operate oil extraction for short time (ex. 30 min) rather than 90 min in terms of comparable extraction yield as well as low chemical consumption.