Effects of Enzymatic Hydrolysis Conditions on the Antioxidant Activity of Red Tilapia (Oreochromis spp.) Viscera Hydrolysates

BACKGROUND: Fish is an essential source of nutrients for human nutrition due to the composition of proteins, vitamins, and minerals, among other nutrients. Enzymatic hydrolysis represents an alternative for the use of by-products of the aquaculture industry. OBJECTIVE: We propose to evaluate the effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity of red tilapia (Oreochromis spp.) viscera hydrolysates. METHODS: The effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity was evaluated using an experimental design that was adjusted to a polynomial equation. The hydrolysate was fractioned to determine the antioxidant activity of the fractions, and functional properties were also measured. RESULTS: Stirring speed and protein concentration presented a statistically significant effect (p <0.05) on all the response variables. However, the temperature did not present a statistically significant effect on the degree of hydrolysis. DISCUSSION: The best conditions of hydrolysis were stirring speed of 51.44 rpm, a temperature of 59.15°C, and the protein concentration of 10 g L-1. The solubility of the hydrolysate protein was high at different pH, and the hydrolysate fraction with the highest antioxidant activity has a molecular weight <1 kDa. CONCLUSION: The degree of hydrolysis and the biological activity of red tilapia viscera hydrolysates (Oreochromis spp.) are affected by temperature, substrate concentration, and stirring speed. The optimal conditions of hydrolysis allowed to obtain a hydrolysate with antioxidant activity are due to the peptides with low molecular weight.