Abstract:

 The fresh meat of Epinephelus was hydrolyzed with alkaline protease to prepare peptides. Based on degree of
hydrolysis and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, an orthogonal design combined with
single facto experiments was applied to optimize enzymatic hydrolysis conditions for peptide preparation. Antioxidant
activities of peptides were evaluated by four different methods, DPPH, 2,2’-azinobis (3-ethylbenzothi azoline-6-sulfonic
acid) ammonium salt (ABTS) and hydroxyl radical scavenging assays, and potassium ferricyanide reduction method. The
results showed that the optimum hydrolysis conditions were 55 ℃, 9, 5 000 U/g, 8 g/100 mL and 5 h for temperature, initial pH,
enzyme dosage, substrate concentration and hydrolysis duration, respectively. The antioxidant activity assays showed that the
hydrolysates presented strong antioxidant activity. DPPH radical scavenging activity, ABTS radical cavenging activity, hydroxyl
radical scavenging activity and potassium ferricyanide reducing power of hydrolyzates from Epinephelus meat were concentration
dependent. The half inhibitory concentration (IC50) for DPPH radical scavenging activity, ABTS radical scavenging activity and
hydroxyl radical scavenging activity were (1.18±0.26), (0.89±0.05) and (0.35±0.02) mg/mL, respectively.

Key words: ice-stored Epinephelus meat, peptides, degree of hydrolysis, scavenging rate, antioxidation