Fish Protein Hydrolysate from Sulfated Polysaccharides Extraction Residue of Tuna Processing By-Products with Bioactive and Functional Properties.

The ethanol-induced precipitation after enzymatic hydrolysis commonly used for sulfated polysaccharide extraction from marine resources wastes a large amount of proteins. Here, possible extraction of fish protein hydrolysates (FPH) from the ethanol residue of sulfated polysaccharide precipitation from head, bone, and skin of skipjack tuna is investigated. Antioxidant, antibacterial, angiotensin I-converting enzyme (ACE) inhibitory activities and functional properties of the recovered FPHs are also evaluated. A degree of hydrolysis of 40.93, 38.13, and 37.23 is achieved for FPH from head, bone, and skin, respectively. FPH from the head presents the highest antioxidant and ACE inhibitory activity as well as foam/emulsion capacity among all the FPHs. The FPHs are all able to inhibit three Gram-positive bacteria and three Gram-negative bacteria to varying degrees and have a water solubility >65%. Altogether, the results demonstrate great potential for recovery of bioactive/functional peptides from the residue of sulfated polysaccharide extraction process enabling efficient biorefining of aquatic resources.