Ultrasound-assisted extraction of halal gelatin from chicken skin using citric acid: A comparative study with conventional waterbath processing

Gelatin is an important biopolymer widely used in food and pharmaceutical industries; however, conventional mammalian sources raise halal and sustainability concerns. Chicken skin, a major poultry by-product, represents a promising alternative source of halal gelatin. This study aimed to evaluate and compare ultrasound-assisted extraction (UAE) and conventional waterbath extraction (CWE) of gelatin from chicken skin using citric acid as a green solvent. Extraction was performed using 0.1 M citric acid, with CWE conducted at 65 °C for 10–30 min and UAE at 42 kHz (35 W) for 10–50 min. The extracted gelatin was characterized in terms of yield, moisture, ash, pH, viscosity, and molecular characteristics using FTIR and SDS-PAGE. UAE produced a significantly higher gelatin yield (8.78 ± 0.80%) than CWE (5.05 ± 0.19%) (p < 0.05). Both extraction methods yielded gelatin with moisture (9.51–10.21%), ash (1.61–1.69%), and pH (4.05–4.34) values within international standards. Viscosity values of 10.15–10.25 cP indicated good thickening properties. FTIR spectra confirmed the presence of characteristic amide bands, while SDS-PAGE analysis revealed dominant α-chain bands in the range of approximately 90–123 kDa, particularly in the unheated UAE sample, indicating that the extraction conditions effectively preserved the molecular integrity of gelatin. These results demonstrate that ultrasound-assisted extraction under mild conditions enhances gelatin recovery from chicken skin while maintaining desirable physicochemical and structural properties, supporting its potential application in halal-oriented food and pharmaceutical products.