Production and characterisation of gelatin from skins of Sin Croaker and Shortfin Scads / Norizah Mhd. Sarbon

This study was undertaken with the purpose of extracting, determining the physico-chemical properties of gelatin from Carangidae (Decapterus Macrosoma bleeker), Shortfin Scads, Selayang and Scianidae (Jhoniecops Sina), Sin Croaker, Gelama. The extraction was carried out by a series of steps, which included washings with 0.2% (w/v) NaOH followed by 0.2% (w/v) H2S04 and 1.0% (w/v) citric acid. The gelatin were extracted at 40-50°C for 12 h. Physicochemical properties of gelatin such as chemical composition, colour, pH, amino acid profile, bloom value, thermal and viscoelastic properties were determined. The yields of gelatin obtained from Sin Croaker and Shortfin Scads skins were 14.25 and 7.25% respectively. The fish gelatin extracted had yellowish in colour and light-textured in appearance which is similar to the commercial gelatin. Thermal properties of gelatin were studied by using Differential Scanning Calorimetry (DSC) and rheometer. Melting and gelling temperature of gelatin from DSC and rheometer was similar. After holding for 2 h at 5°C, melting temperature of fish gelatins was tremendously increased by about 1.5 times while bovine gelatin only increased by about 0.5 times. Gelling and melting temperatures were increased with the addition of CaSC^ and MgSC>4 salts and decreased with the addition of CaCh salts. However, there were no effects in gelling and melting temperatures of bovine gelatin when CaS04 and MgSC>4 were added as compared to fish gelatins. Storage modulus (G') of fish gelatins were observed greatly increased by more than 10 folds after holding for 2 h at 5°C while storage modulus (G') for bovine gelatin only double. Viscous modulus (G") increased 6 times for both Shortfin Scads and Sin Croaker gelatin compared to bovine gelatin only increased about 2 times after holding for 2 h at 5°C. CaCb addition to the gelatin solution decreased the moduli of gelatins and resulted in the no gelling ability to Sin Croaker gelatin at 0.4M concentration. The addition of CaSC>4 and MgS04 improved the storage modulus (G') of Shortfin Scads and Sin Croaker gelatins higher than that of bovine gelatin. The bloom value which is the large deformation of gel after storing for 18 h at 7°C gave similar results as the viscoleastic studies. The findings in this study revealed that fish gelatin solution had rheological properties greatly improved after holding for 2 h at 5°C. MgSC>4 can be used to improve the bloom value, elastic and viscous moduli of the fish gelatin. Shortfin Scads gelatin had better thermal and rheological properties than Sin Croaker gelatin.