Valorization of Rohu ( Labeo rohita ) Fish Scale Waste Through Gelatin Extraction: Physicochemical, Thermal, Rheological, and Functional Characterization

Fish scales are collagen-rich processing by-products with considerable potential as a sustainable source of non-mammalian gelatin. This study aimed to extract gelatin from Rohu ( Labeo rohita ) fish scales and comprehensively characterize its physicochemical, thermal, structural, rheological, textural and functional properties for potential food and industrial applications. Gelatin was extracted by acid demineralization followed by hot-water extraction and characterized using physicochemical analyses, Fourier transform infrared spectroscopy (FTIR), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), texture profile analysis (TPA) and functional property measurements. The extracted gelatin exhibited a yield of 21.86%, a protein content of 88.37%, an ash content of 1.5%, a gel strength of 182.82 g, a viscosity of 6.56 cP, a solubility of 87.49%, a melting temperature of 23.38 °C, a setting temperature of 20.4 °C and a setting time of 660 s. FTIR and SDS–PAGE confirmed the characteristic structural features of type I collagen-derived gelatin with well-preserved α 1 , α 2 and β chains. The gelatin also demonstrated favorable water-holding capacity (169.70%), fat-binding capacity (188.50%), foaming capacity (193.33%) and foaming stability (77.65%), while emulsion capacity and stability increased with gelatin concentration, reaching 44.11% and 42.15%, respectively, at a gelatin concentration of 2.0%. These findings demonstrate the potential of Rohu fish scale gelatin as a sustainable, value-added non-mammalian biomaterial for food, packaging, pharmaceutical and related industrial applications while promoting the valorization of fish-processing waste.