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. This study proves that the ethanol residue remaining during polysaccharide extraction from skipjack tuna by‐products can be a source for parallel extraction of protein hydrolysates with good bioactivity and functional properties and can be employed as a natural source of antioxidant and antibacterial compounds that can be used in the food and nutraceutical industries.