Gelatin Production from Rainbow Trout (Oncorhynchus mykiss) Skins and Evaluation of Its Technological Properties

Abstract

Gelatin production from fish-processing by-products has gained attention as a sustainable strategy for value-added utilization of aquatic resources. In this study, gelatin was extracted from rainbow trout (Oncorhynchus mykiss) skins and its physicochemical, structural, and functional properties were evaluated in comparison with commercial bovine gelatin. Compared with bovine gelatin (220±3.00 g), trout gelatin displayed a milder gel network characterized by a gel strength of 95.1±5.00 g, a pH of 4.78±0.23, and a water-holding capacity of 13.92±0.73 mL water/g protein, reflecting distinct structural and functional behavior rather than reduced quality. In contrast, the high protein content (95.30±0.41%) indicated considerable compositional purity. Functional analyses revealed distinct interfacial advantages for trout gelatin. Oil-binding capacity was significantly higher (1.17±0.10 mL oil/g protein) than that of bovine gelatin (P<0.05). Although emulsifying activity index and initial foaming capacity were similar or lower, trout gelatin demonstrated markedly greater emulsion stability and long-term foam stability (P<0.05). Zeta potential values were low for both gelatins, suggesting that stabilization mechanisms were governed more by steric interactions and viscoelastic interfacial film formation than by electrostatic repulsion. FTIR spectra showed characteristic amide bands (amide I, II, III, A, and fingerprint regions) in both samples, confirming successful conversion of collagen to gelatin and indicating comparable chemical structures. Therefore, the observed functional differences are likely associated with molecular organization and amino acid composition rather than major structural variations. Overall, rainbow trout skin gelatin can be considered a promising alternative to bovine gelatin, particularly in food systems where emulsion and foam stability or lipid interaction are more critical than high gel strength. Its production from processing by-products also supports sustainable waste valorization in the food industry.

Keywords

• Rainbow trout gelatin
• Fish by-products
• Technological properties
• Gel strength
• Emulsion
• Foaming

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