Isolation and characterization of gelatin from the skins of skipjack tuna (Katsuwonus pelamis), dog shark (Scoliodon sorrakowah), and rohu (Labeo rohita)

Gelatin was extracted from the skins of dog shark ( Scoliodon sorrakowah ), skipjack tuna ( Katsuwonus pelamis ) and rohu ( Labeo rohita ) and their physico-chemical properties were measured. The skins of shark, tuna and rohu yielded 19.7, 17.2 and 11.3% gelatin, respectively. The gel strength of dog shark gelatin (6.67%, 10 °C) was found to be higher (206 g) than tuna and rohu skin gelatins (177 g and 124 g, respectively). Similarly, molecular weight, viscosity, melting point, foaming properties, water holding capacity, odour, colour and clarity of dog shark gelatin were in general better than the tuna and rohu skin gelatins. The amino acid analysis showed that hydroxyproline content in dog shark skin gelatin was the highest when compared to tuna and rohu skin gelatins.