Objective Physiochemical properties and functional activities of the enzymatically hydrolyzed cooking drips from tuna processing were analyzed in vitro to evaluate the potential of byproduct utilization.

Method Six proteases were used to hydrolyze the drips from steam-cooking tuna. Physiochemical properties as well as functional activities of the hydrolyzed liquid were analyzed.

Result The protease-digestion on the tuna cooking drips did not affect the DPPH radical scavenging ability or xanthine oxidase inhibition but significantly raised the ABTS radical scavenging ability of the resulting liquid. Among all proteases tested, the pineapple protease had the highest EC50 on free radical scavenging of 0.24 mg·mL⁻¹, but the animal hydrolyzed protease or trypsin delivered the greatest effect on bone cell proliferation. At a volume concentration of acid-soluble protein in the enzyme digestion product at 1mg·mL⁻¹, the animal hydrolyzed protease produced an osteoclast proliferation rate of 133.78%, while trypsin yielded 132.13%. Although the difference between the two proteases was not significant, extremely significant differences existed in comparison to the other proteases.

Conclusion Certain activity of osteoclast proliferation, rather than antioxidant and xanthine oxidase inhibition, was shown in the in vitro physicochemical and functionality examinations on the enzymatically hydrolyzed tuna cooking drips. It indicated a potential for developing functional peptides from the byproduct of tuna processing.