Optimization of gelatin production from Barred mackerel by-products: Characterization and hydrolysis using native and commercial proteases

In this study, gelatin production was optimized at three levels of time and temperature using the response surface method (RSM) by considering the yield, protein content, gel strength, and viscosity. Afterward, gelatin was manufactured at optimum conditions (70.71 °C and 5.85 h). Gelatin characterization showed acceptable rheological, structural, and functional properties compared to the commercial bovine gelatin. The hydrolysis of gelatin was performed by actinidin extracted from kiwifruit and alcalase at their optimum conditions. Enzymatic hydrolysis using alcalase followed by actinidin (ALC-ACT) resulted in 3–10 kDa hydrolysates which showed antioxidant and anticancer activities of 67.75% and 96.93%, respectively, at the concentration of 1 mg mL⁻¹. The degree of hydrolysis for the ALC-ACT hydrolysates was 33.34%. The resultant hydrolysates were further purified by RP-HPLC and 9 fractions were obtained. The F₁ fraction eluted at 5.05 min had the highest intensity and bioactivity (97.68% and 82.98% anticancer and antioxidant activity, respectively, at the same concentration). The results showed that hydrolysis lowered the surface tension to 34.19 mN/m. The rehydration ratio (RR) of gelatin and its hydrolysates were increased as a function of rehydration time.