Biometric Indicators, Gelatin Yield, and Functional Properties of Fish Scale Waste from Three Species with Different Trophic Levels

Gelatin is a widely used food additive due to its ability to form gels and provide elastic texture to various food and feed products. This study evaluated the biometric characteristics as well as the physicochemical and functional properties of gelatin derived from waste scales of Puntioplites bulu fish (herbivore), Cyprinus carpio (omnivore), and Channa lucius (carnivore). The scales were first treated with 3% (v/v) glacial acetic acid and extracted with distilled water (1:4, w/v) at 80 °C for four hours. Fulton's condition factor ranged from 1.13 to 3.30. The length-weight relationship showed positive (+) and negative (-) allometric growth patterns. The average gelatin yield (based on wet weight) was 12.35% (P. bulu), 7.13% (C. carpio), and 5.03% (C. lucius). The extracted gelatin had an acidic pH (6.09–6.28). The foaming ability (FA) and foam stability values were: P. bulu (613.33% and 83.42%), C. carpio (416.67% and 28.3%), and C. lucius (550% and 73.06%). Furthermore, the water holding capacity (WHC) and fat binding capacity (FBC) of fish scale gelatin were 777.33% and 98.33% (P. bulu), 312% and 37.66% (C. carpio), and 967.0% and 207.33% (C. lucius), respectively. The gel strength and viscosity of P. bulu (226.67 g and 4.83 cP), C. carpio (207.33 g and 5.37 cP), C. lucius (278.33 g and 6.90 cP). In conclusion, gelatin from fish scale waste at different trophic levels exhibits varied biometric, physicochemical, and functional properties, with potential applications in human and animal food industries.