Optimization of the Ultrafiltration Process of Antioxidant Peptide Fractions from Red Tilapia (Oreochromis spp.) Scale Hydrolysates

This study investigated scaling up of the process from the laboratory to the bench scale and optimized the fractionation of antioxidant hydrolysates from tilapia scales gelatin. Gelatin was extracted via hydrothermal processing, then hydrolyzed with Alcalase® and fractionated using a 1-kDa MWCO tangential flow filtration system. The effects of transmembrane pressure, pH, and feed flow rate on membrane performance, peptide characteristics, and transfer of antioxidant activity were studied. The scale-up from the laboratory to the bench scale was successfully achieved. Similar protein, free amino group content and degree of hydrolysis (DH) were observed at both scale processes, confirming the reliability of the system (86.45 ± 0.25% of protein, 0.25 ± 0.01 mM eq. NH2, 21.21 ± 0.47 % of DH). Experimental design data revealed that the majority of the fitted models showed good accuracy in predicting responses, with coefficients of determination (R2) greater than 0.8. The optimized ultrafiltration conditions were 1.98 bar TMP, a pH of 10, and a feed flow rate of 483 L/h, with relative errors below 20%, indicating satisfactory model predictability. The < 1 kDa fraction obtained with the former optimal conditions exhibited significantly higher Fe2+-chelating, TEAC, and FRAP activities, suggesting an enrichment of peptides with significant electron donating and metal-binding activities. However, the ORAC activity did not increase in the permeate, likely due to differences in peptide structure and radical-scavenging mechanisms. This finding suggests that the < 1 kDa fraction hydrolysate from tilapia scale gelatin has the potential as a bioactive ingredient and could be further investigated as functional foods or as nutraceuticals.