The effect of added salts on the viscoelastic properties of fish skin gelatin

The effects of various salts on the viscoelastic properties of a class A gelatin (obtained by a mild acid pretreatment) from megrim (Lepidorhombus boscii) skins were examined and compared with their effects on commercial tilapia skin gelatin. Although salts generally extended the setting time of gelatins, it was found that the melting temperature was increased considerably by the addition of MgSO4, (NH4)2SO4, or NaH2PO4. Of all the salts assayed, only MgSO4 improved the rheological characteristics in suitable conditions of pH and ionic strength, which differed between megrim and tilapia gelatin. Notable differences were found in the amino acid compositions of the two species, especially in the hydroxyproline content.