## 3 Results and Discussion
### Simultaneous Protein and Lipid Hydrolysis
#### 3.4.1 Recovered Products  
Meat waste hydrolysis, with a combination of Alcalase and Resinase, fractionated the proteinic and lipidic materials into a solid fraction containing mainly collagen, a water-liquid fraction enriched with solubilized proteins (indicative of the quantity of generated protein hydrolysate according to [PERSON] et al. (1998), and a lipid-liquid fraction that was mainly present as free fatty acids. The percentage recovery was calculated as the recovered compound amount divided by the initial compound amount in meat waste, being these compounds: solubilized proteins, collagen, and lipids.  
The recovery of lipids in the lipid liquid fraction after hydrolysis varied between 86% for experiment number 1 (pH = 7.5, T = 45 \({}^{\circ}\)C, _Eo_/_So_ = 0.11 AU/g, and _Eo_/_So_\({}^{\prime}\)= 0.55 kLU/g) and 97% for experiment number 9 (pH = 8.0, T = 45 \({}^{\circ}\)C, _Eo_/_So_ = 0.21 AU/g, and _Eo_/_So_\({}^{\prime}\)= 1.11 kLU/g) (Figure 6). Obviously, higher _Eo_/_So_\({}^{\prime}\) ratios (higher concentrations of Resinase in relation to the lipidic substrate concentration) favor the lipids recovery, but the addition of Alcalase in the reactor also helps to increase the amount of recovered lipids: proteases break the peptide bonds, resulting in the release of lipids from meat waste; the bigger the cleavage of the peptide bond, the higher the amount of lipids released ([PERSON] et al., 2010).  
The variation of collagen recovery in the solid fraction was much higher, between 42% for experiment number 9 (pH = 8.0, T = 45 \({}^{\circ}\)C, _Eo_/_So_ = 0.21 AU/g, and _Eo_/_So_\({}^{\prime}\)= 1.11 kLU/g) and 61% for experiment number 2 (pH = 8.0, T = 50 \({}^{\circ}\)C, _Eo_/_So_ = 0.11 AU/g, and _Eo_/_So_\({}^{\prime}\)= 0.83 kLU/g) (Figure 6). The lower recoveries in hydrolysis with the highest _Eo_/_So_ ratios (experiments 7, 8, and 9) indicate a significant protein conversion to other products, such as peptides or amino acids. These results are confirmed by the variation of solubilized protein in the water-liquid fraction, which was between 50% for experiment number 2 (pH = 8.0, T = 50 \({}^{\circ}\)C, _Eo_/_So_ = 0.11 AU/g, and _Eo_/_So_\({}^{\prime}\)= 0.83 kLU/g) and 69% for experiment number 9 (pH = 8.0, T = 45 \({}^{\circ}\)C, _Eo_/_So_ = 0.21 AU/g, and _Eo_/_So_\({}^{\prime}\)= 1.11 kLU/g). As expected, hydrolysis of proteins is favored by high _Eo_/_So_ ratios (higher concentrations of Alcalase in relation to the proteinic substrate concentration); however, the percentage of hydrolyzed protein is also favored by Resinase's presence in the reactor. The split of the triglyceride bonds via lipases caused the protein release from meat waste; consequently, peptide bonds are more exposed and vulnerable to proteases (Bhydrolysis at high _Eo/So_ and _Eo'_/_So'_ ratios, specifically at the conditions of pH = 8.0, T = 45 \({}^{\circ}\)C, _Eo/So =_ 0.21 AU/g, and _Eo'_/_So'_ = 1.11 kLU/g, are more suitable for achieving high recoveries of the solubilized proteins (that is, protein hydrolysate) and lipids from meat waste. On the contrary, enzymatic hydrolysis at low _Eo/So_ and _Eo'_/_So'_ ratios, specifically at the conditions of pH = 8.0, T = 50 \({}^{\circ}\)C, _Eo/So =_ 0.11 AU/g, and _Eo'_/_So'_ = 0.83 kLU/g, are more suitable to achieve high recovery of collagen.