Effects of Ultrasound-Assisted Extraction on Physicochemical and Functional Properties of Gelatin Derived from Hilsha (Tenualosa ilisha) Scales

Gelatin is a multifunctional protein with numerous applications in the food and pharmaceutical industries. The increased global demand for gelatin and issues regarding mammalian collagen have prompted an imperative urge for alternative sources. Therefore, this study aimed to explore the impact of ultrasound-assisted extraction on the physicochemical, functional, and bioactive attributes of gelatin obtained from Tenualosa ilisha scales. Ultrasound-assisted gelatin (UAG) extraction substantially increased the yield (34.49%), reducing fat and moisture content compared to water bath gelatin (WBG) extraction (20.06%). Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed alpha 1, alpha 2, and beta chains, corroborating a triple helical conformation with UAG displaying shorter peptide composition. Fourier-transform infrared spectroscopy (FT-IR) showcased distinct peaks for amide- I, II, III, and A with decreased molecular order owing to ultrasound treatment. The WBG exhibited a lower UV-transmittance and a higher gel melting temperature, whereby, UAG displayed an excellent foaming capacity and stability with improved performance at higher concentrations. The WBG demonstrated superior emulsion activity and stability index, however, the emulsion activity of both gelatins declined with increasing concentrations. The gelatins showed a similar water-holding capacity, although WBG possessed a greater fat-binding capacity compared to UAG. However, UAG demonstrated enhanced antioxidant effects, revealing an IC50 of 121.17 +/- 2.38 for scavenging free radicals and an EC50 of 184.48 +/- 3.16 for reducing Fe3+, thus, minimizing oxidative stress. The findings will offer novel insights into the influence of ultrasound treatment on the properties of fish scale gelatin and developing methods for tailoring scale gelatin for food and pharmaceutical interventions.