Influence of Enzyme Type and Hydrolysis Time on Antioxidant Activity of Hydrolyzed Protein from Longtail Tuna (Thunnus tonggol) Dark Muscle

Aim: In this study, the antioxidant properties of hydrolyzed protein from longtail tuna dark muscle with commercial enzymes (alcalase, alkaline protease, and evatase) were investigated. Materials Methods: Protein hydrolysates from tuna dark muscle were prepared by different enzymes Degree of hydrolysis (DH) was performed by TCA technique. The five aliquots at 60, 180, 240, 300, and 360 min were gathered during hydrolysis. The antioxidant activity of aliquots was monitored by in vitro assays (DPPH inhibition ability and Ferric (Fe3+) reducing power). Findings: The antioxidant activities of protein hydrolysate from tuna dark muscle (TDM) increase with increasing time and DH. Alcalase hydrolyzed protein (AHP) generally showed higher antioxidative activity than evatase hydrolyzed protein (EHP) and alkaline protease hydrolyzed protein (APHP). Among the samples (concentration 3 mg.ml-1), AHP at 360 min significantly exhibited the highest ability to scavenge DPPH radical (72.6 %). Furthermore, AHP and APHP significantly showed a minimum IC50 value of 1.1 mg.ml-1 at 240 and 360 min hydrolysis. APHP significantly exhibited the highest ferric reducing power of 0.83 at 300 min and 0.76 at 240 min. AHP and APHP significantly showed the highest ferric reducing power of 0.74 at 360 min (p 0.05). Conclusion: This study confirmed that protein hydrolysate from TDM could be a good source of antioxidant peptides. In addition, the antioxidant activity of hydrolyzed protein relay on protease type and hydrolysis condition.