Extraction, physicochemical, thermal, and rheological characterization of gelatin from milkfish (Chanos chanos) skin using different pretreatment and extraction methods

The study investigated the extraction and characterization of gelatin from milkfish skin ( Chanos chanos ) using different pretreatment and extraction methods. The effects of acetic acid, combined sulfuric acid-acetic acid pretreatments, ultrasound-assisted extraction, and optimized multi-step extraction were evaluated. Extraction conditions significantly affected gelatin yield and functional properties. The highest yield (42.63 ± 1.63%) was obtained using ultrasound-assisted extraction combined with sulfuric acid and acetic acid pretreatment. Ultrasound treatment also improved the thermal and rheological properties of gelatin, resulting in higher melting (33.30 °C) and gelling temperatures (19.70 °C). Gelatin produced using acetic acid pretreatment and ultrasound exhibited greater viscosity (11.92 cP) and gel strength (219.57 g) than gelatin obtained through conventional extraction methods. Color analysis showed ΔE* values ranging from 55.37 to 59.19, indicating retention of the natural gelatin pigmentation. Overall, ultrasound-assisted extraction combined with appropriate acid pretreatment enhanced gelatin yield and improved its physicochemical, thermal, and rheological characteristics.