## 4 Conclusions  
Enzymatic hydrolysis process can be effectively used as a green technology to recover products like protein hydrolysate, collagen, and fatty acids from meat wastes, thus reducing the organic load caused by meat retail stores, solving the pollution problem, and supporting the circular economy of the sector. Enzymatic hydrolysis has the advantage that it can recover the proteins (hydrolysate and collagen) and the fatty acids either separately or simultaneously, using a protease, a lipase, or a combination of protease and lipase. In this work, the protease Alcalase and the lipase Resinase were used separately or combined to hydrolyze meat waste. The use of a combination of Alcalase and Resinase for the hydrolysis has the additional advantage of recovering all the products in a sole stage. The protein hydrolysates obtained, which are rich in low molecular weight peptides (average molecular weight near 500 Dalton), are suitable for the food industry. The lipids recovered are rich sources of unsaturated fatty acids which have several health benefits. Additionally, recovered collagen could be used in a variety of fields, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Product**} & \multicolumn{6}{c}{**Amount of Product (kg\({}_{\text{prod}}\)/kg\({}_{\text{dry meat waste}}\))**} \\ \cline{2-10}  & \multicolumn{6}{c}{**Experiment No**} \\ \cline{2-10}  & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** \\ \hline Protein hydrolysate & 0.1000 & 0.0950 & 0.1010 & 0.0960 & 0.1120 & 0.1280 & 0.1230 & 0.1260 & 0.1320 \\ Unhydrolyzed collagen & 0.0047 & 0.0049 & 0.0045 & 0.0048 & 0.0041 & 0.0037 & 0.0038 & 0.0037 & 0.0034 \\ C14:0 & 0.0189 & 0.0189 & 0.0201 & 0.0194 & 0.0212 & 0.0215 & 0.0211 & 0.0213 & 0.0209 \\ C15:0 & 0.0008 & 0.0008 & 0.0009 & 0.0009 & 0.0009 & 0.0009 & 0.0009 & 0.0009 & 0.0009 \\ C16:0 & 0.1303 & 0.1282 & 0.1467 & 0.1442 & 0.1545 & 0.1586 & 0.1591 & 0.1525 & 0.1593 \\ C16:1 & 0.0006 & 0.0006 & 0.0007 & 0.0007 & 0.0007 & 0.0007 & 0.0007 & 0.0007 & 0.0007 \\ C17:0 & 0.0113 & 0.0120 & 0.0126 & 0.0125 & 0.0134 & 0.0135 & 0.0131 & 0.0135 & 0.0133 \\ C17:1 & 0.0026 & 0.0027 & 0.0027 & 0.0028 & 0.0031 & 0.0031 & 0.0030 & 0.0031 & 0.0031 \\ C18:0 & 0.0923 & 0.0939 & 0.0947 & 0.0935 & 0.0988 & 0.0975 & 0.0972 & 0.0986 & 0.0981 \\ C18:1 & 0.1615 & 0.1641 & 0.1634 & 0.1667 & 0.1664 & 0.1721 & 0.1619 & 0.1660 & 0.1749 \\ C18:2 & 0.0899 & 0.0902 & 0.0931 & 0.0942 & 0.0948 & 0.0998 & 0.0995 & 0.0984 & 0.0979 \\ C18:3n3 & 0.0228 & 0.0244 & 0.0255 & 0.0258 & 0.0273 & 0.0281 & 0.0274 & 0.0277 & 0.0276 \\ C18:3n6 & 0.0003 & 0.0003 & 0.0003 & 0.0003 & 0.0004 & 0.0004 & 0.0004 & 0.0004 & 0.0004 \\ C20:0 & 0.0022 & 0.0022 & 0.0023 & 0.0023 & 0.0024 & 0.0024 & 0.0024 & 0.0023 & 0.0024 \\ C20:2 & 0.0194 & 0.0196 & 0.0201 & 0.0202 & 0.0207 & 0.0211 & 0.0206 & 0.0208 & 0.0207 \\ C20:3n3 & 0.0199 & 0.0202 & 0.0203 & 0.0200 & 0.0210 & 0.0208 & 0.0210 & 0.0208 & 0.0208 \\ C20:3n6 & 0.0121 & 0.0121 & 0.0132 & 0.0131 & 0.0149 & 0.0152 & 0.0144 & 0.0137 & 0.0147 \\ C20:4n6 & 0.0113 & 0.0120 & 0.0131 & 0.0132 & 0.0140 & 0.0154 & 0.0145 & 0.0141 & 0.0153 \\ Total & 0.7009 & 0.7021 & 0.7352 & 0.7306 & 0.7706 & 0.8028 & 0.784 & 0.7845 & 0.8064 \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Obtention of products after hydrolysis with a combination of Alcalase and Resinase. including biomedical and aesthetic ones. In any case, the recovered products have potential application in cosmetic and biotechnology applications. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13158763/s1](https://www.mdpi.com/article/10.3390/app13158763/s1)]([https://www.mdpi.com/article/10.3390/app13158763/s1](https://www.mdpi.com/article/10.3390/app13158763/s1)), Table S1. Relative deviation of molecular weight (_MM_) with respect to 500 Daltons for hydrolyses obtained using different pHs and temperatures (T). Table S2.