Background and Objectives: Bioactive peptides in the protein hydrolysate lead to high antioxidant activity of these proteins. Food waste can be used as a potential material for the production of bioactive peptides. The aim of this study was to produce protein hydrolysate of yellowfin tuna viscera in optimal conditions and analyze its antioxidant activity.
 Materials & Methods: After performing the preparation of viscera yellowfin tuna to optimize the production of protein hydrolysates with an emphasis on the antioxidant properties using response surface method based on central composite design. Four factors (pH, temperature, reaction time and enzyme to substrate ratio) were used for optimization. Peptide chain length and antioxidant properties (measured by free radical scavenging activity and reducing power assay test) of hydrolyzed protein were measured.
Results: The impact of each variable (pH, temperature, reaction time and ratio of enzyme to substrate) on the amount of antioxidant properties and peptide chain length was significant (p <0/05). However, there was no direct correlation between the two parameters. The high correlation coefficient 982.0 (antioxidant properties) and 967.0 (peptide chain length) showed a good ability to be a model to predict reaction conditions. According to the results, the optimum treatment for free radical scavenging activity DPPH was 43.81 (µmol Trolox equivalents TE/g), FRAP 1.0 (Absorbance at 700 nm) and peptide chain length was 98.2 (Run 10).
Conclusion: The most important role in regards to the antioxidant activity, are the inherent properties of protein hydrolysates.