Effect of Treatment with Ultrasonic Pulses on the Functional Properties and Antioxidant Capacity of Dogfish (Galeorhinus galeus) Viscera Proteins

The valorization of fish by products represents a sustainable strategy forobtaining high value functional ingredients. The viscera of Galeorhinus galeuswere evaluated as a source of protein hydrolysates with nutritional andbioactive potential. The objective was to determine the impact of ultrasonicpretreatment on proximate composition, antioxidant activity, and technofunctional properties of enzymatic hydrolysates. Viscera were subjected toautohydrolysis with and without ultrasonic pulses. Proximate composition wasanalyzed, antioxidant activity was assessed by DPPH and FRAP assays, and thedegree of hydrolysis (DH) was quantified. Protein degradation was evaluated bySDS-PAGE, while foaming and emulsifying capacities were determined asindicators of functional performance. Ultrasound significantly improved proteinsolubilization, increasing DH to 28.4% compared with untreated controls.Antioxidant activity was enhanced, with ultrasound-treated hydrolysatesreaching up to 97.8% radical inhibition at acidic pH and moderate hydrolysistimes. Electrophoretic analysis confirmed progressive fragmentation into lowmolecular-weight peptides, consistent with the observed increase in DH.Techno-functional evaluation showed a marked improvement in foamingcapacity (from 24% to 97%), whereas emulsifying capacity decreased (<25%)due to disruption of amphipathic structures. These findings demonstrate thatultrasound-assisted hydrolysis enhances the nutritional, antioxidant, and technofunctional properties of shark viscera proteins. This approach provides asustainable alternative for generating protein ingredients with potentialapplications in food formulations and nutraceutical development.