Highly Digestible Protein from Oncorhynchus Mykiss Residues by Mechanical Separation

The generation of fish waste, particularly from aquaculture, poses a significant environmental and nutritional challenge. This study aimed to valorize trout (Oncorhynchus mykiss) viscera by producing and characterizing protein hydrolysates concentrated via mechanical separation. Six treatments were applied by varying the degree of hydrolysis (DH) and separation. Method: T1 (DH 40–45%, centrifugal separator), T2 (DH 40–45%, Tricanter simulator), T3 (DH 50–55%, centrifugal separator), T4 (DH 50–55%, Tricanter simulator), T5 (DH 60–65%, centrifugal separator), and T6 (DH 60–65%, Tricanter simulator). Nutritional composition (crude protein, ether extract, ash, crude fiber, and nitrogen-free extract), microbiological safety, in vitro digestibility, and oxidative rancidity were analyzed. All treatments yielded hydrolysates with over 60% crude protein. T3, T5, and T1 achieved the highest protein concentrations, with T4 standing out for its low ether extract content and favorable balance of nutritional and microbiological properties. The T4 hydrolysate showed approximately 65% protein and 90.71% in vitro digestibility, indicating a high nutritional value. These findings highlight the potential of enzymatic hydrolysis combined with mechanical separation as an efficient strategy to transform trout viscera waste into high-value protein ingredients for animal feed applications.