Purity and properties of gelatins extracted from the head tissue of the hybrid kalamtra sturgeon

The head is a major by-product (17.1% of body weight) of sturgeon aquaculture farming and remains unutilized. In this study, the sturgeon head was separated into the skull cartilage and mixed tissue: skin, scales, fins, muscles, bones, gills, and small cartilage pieces. Type A and B gelatins were extracted from the mixed tissue. The type B yield was higher, at 5.8% gelatin dry weight per tissue wet weight. The relative gelatin content in the sample weight, estimated from the sample's hydroxyproline content relative to that of the purified collagen, was higher in type A (60.3%) than in type B (39.7%). Type A gelatin showed higher intensities of the α- and β-bands of gelatin in SDS-PAGE, indicating that gelatin purity was higher in type A. The breaking force-strain curve showed a larger breaking force and lower breaking strain in type A (2.0 N, 12.1%), indicating that this gelatin is stronger than type B (0.7 N, 15.8%). Type B gelatin featured higher emulsion activity and stability and higher foam expansion and stability. In conclusion, type A and B gelatins with distinct proximate composition and functional properties were successfully extracted from sturgeon heads, which could act as a promising source of gelatins for industrial applications.