Effects of different types and concentration of salts on the rheological and thermal properties of sin croaker and shortfin scad skin gelatin

The aims of this study were to examine the effect of salts (CaCl2, CaSO4 and MgSO4) on the rheological and thermal properties of gelatin extracted from the skins of tropical fishes, sin croaker (Johnius dussumeiri) and shortfin scad (Decapterus macrosoma). It was found that the melting temperatures of fish skin gelatins were increased by 1.5 times as compared to bovine gelatin which was only increased by 0.5 times after holding for 2 h at 5°C. The storage (G’) and loss (G”) modulus of fish skin gelatins were improved with the addition of calcium sulphate (CaSO4) and magnesium sulphate (MgSO4), respectively. However, the storage (G’) and loss (G”) modulus of gelatin solutions were decreased with the addition of calcium chloride (CaCl2). Magnesium sulphate (MgSO4) was found to be an effective salt to improve the bloom value, elastic and viscous moduli of the fish skin gelatin. This study showed that shortfin scad skin gelatin with salt addition possessed better thermal and rheological properties than sin croaker gelatin.