## 3 Results and Discussion
### Lipid Hydrolysis  
#### 3.3.1 Influence of pH and Temperature  
For this study, the _Eo/So'_ ratio used was 0.83 kLU/g (1.5% g Resinase/g lipids in meat waste). This ratio agrees with the experiments by [PERSON] et al. [68] where 1.0 to 1.5% g of lipase/g lipids were used for hydrolysis of land that was catalyzed by lipase. The experiments were conducted at the same pHs (7.0-9.0 at a temperature of 50 \({}^{\circ}\)C) and temperatures (40-60 \({}^{\circ}\)C at a pH of 8.0) as experiments with Alcalase. These values of pHs and temperatures are within or very close to the optimal range for Resinase (see Section 2.1). The results achieved (Tables 7 and 8) indicate that hydrolysis of lipids is favored by lowering the temperature or by increasing the pH. Table 7 shows that the most suitable pH seems to be around 8.0 because, for higher pHs, there are no significant variations in the percentages of recovered lipids that justify its use. Table 8 indicates that the percentage of recovered lipids in the range from 40 to 55 \({}^{\circ}\)C are relatively close to each other while, for 60 \({}^{\circ}\)C, this percentage is significantly reduced. This suggests that lipolytic hydrolysis should not be carried out at temperatures above 55 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c} \hline _Eo/So_ (**AU/g**) & **PCL** & **MM (Daltons)** \\ \hline
0.09 & 4.35 & 566.08 \\
0.11 & 4.17 & 542.34 \\
0.16 & 3.63 & 471.95 \\
0.21 & 3.45 & 449.05 \\
0.27 & 3.08 & 401.05 \\ \hline \end{tabular}
\end{table} 
Table 6: Average peptide chain length (_PCL_) and molecular weight (_MM_) of the hydrolysates obtained under different protease/proteinic substrate ratios (_Eo/So_). \begin{table}
\begin{tabular}{c c} \hline
**pH** & **Recovered Lipids (\%)** \\ \hline
7.0 & 77.36 \(\pm\) 0.01 \\
7.5 & 91.31 \(\pm\) 0.12 \\
8.0 & 95.40 \(\pm\) 0.33 \\
8.5 & 96.45 \(\pm\) 0.08 \\
9.0 & 97.68 \(\pm\) 0.02 \\ \hline \end{tabular}
\end{table} 
Table 7: Recovery of lipids at different pHs. The behaviour against pH is justified by the great stability of the enzyme in the pH range used [69]. Although the literature indicates that Resinase is active at temperatures up to 90 \({}^{\circ}\)C, it has been verified that, in the presence of waste, lipase inactivation occurs over time with increasing temperature and that inactivation is so high at higher temperatures that the efficiency of the process is less at 60 \({}^{\circ}\)C given the long reaction time. The amounts of fatty acids released as a function of pH and temperature are shown in Tables 9 and 10. As can be appreciated, the free fatty acid amounts follow the same trend as the percentage of recovered lipids: the higher the pH and the lower the temperature, the greater the quantity of individual acids obtained. The influence of pH and temperature on the amounts of fatty acids released in the lipid hydrolysis has also been observed by other researchers [70]. The graphical representations of the total amount of fatty acids released by lipid hydrolysis against the pH and the temperature are displayed in Figures 1 and 2, respectively. They allow us to clearly appreciate how, for pH greater than 8.0 at 50 \({}^{\circ}\)C or temperatures above 50 \({}^{\circ}\)C at pH 8.0, there are no significant variations in the amounts of fatty acids obtained that justify the additional cost of reaching higher quantities of fatty acids. \begin{table}
\begin{tabular}{c c} \hline
**T** (\({}^{\circ}\)**C**) & **Recovered Lipids (\%)** \\ \hline
40 & 98.89 \(\pm\) 0.05 \\
45 & 97.29 \(\pm\) 0.06 \\
50 & 95.39 \(\pm\) 0.34 \\
55 & 87.01 \(\pm\) 0.01 \\
60 & 68.12 \(\pm\) 0.10 \\ \hline \end{tabular}
\end{table} 
Table 8: Recovery of lipids at different temperatures.