A Green Technology Approach Using Enzymatic Hydrolysis to Valorize Meat Waste as a Way to Achieve a Circular Economy

The retail meat industry produces a significant amount of waste, containing proteins, lipids, and other elements that could serve as the basis for other products. This work presents the results of research on the enzymatic hydrolysis of meat waste as a green technology to obtain products with added value as a substitute for other raw materials. pH, temperature, the protease/proteinic substrate ratio (Eo/So), and the lipolase/lipidic substrate ratio (Eo’/So’) were studied as process variables for hydrolysis of proteins and lipids, respectively. Hydrolysis for the recovery of proteins (as protein hydrolysates or collagen) was carried out with the protease Alcalase; pH around 8.0, temperature around 50 °C, and Eo/So around 0.16 AU/g were the optimum process variables’ values for obtaining high amounts of recovered proteins and peptides that are easily digestible and have a pleasant taste. The lipase Resinase was used to hydrolyze the lipids; a clear relationship was observed between Eo’/So’ and the amounts of recovered fatty acids. The optimum process variables’ values were found to be Eo’/So’ around 0.83 kLU/g, pH around 8.0 and temperature around 50 °C. Unsaturated fatty acids prevailed in the final product. For the simultaneous recovery of protein hydrolysates, collagen, and fatty acids, a combination of Alcalase and Resinase was used; the process variables examined included the optimal range of values for Eo/So and Eo’/So’, as well as pH and temperature that were suggested in research for both Alcalase and Resinase, separately. The results showed that the simultaneous process was mainly influenced by the Eo/So and Eo’/So’ ratios, instead of being influenced by the pH and temperature values which were less influential. For Eo/So = 0.16 AU/g, Eo’/So’ = 1.11 kLU/g, pH = 7.5, T = 50 °C, the maximum amounts of products (0.8 kg by kg of dry meat waste) were obtained more economically, where the whole of the proteins and lipids in meat waste were practically recovered. Therefore, in order to preserve a circular economy for retail meat waste, enzymatic hydrolysis is appealing and environmentally friendly.