Rheological Properties of Gelatin from Silver Carp Skin Compared to Commercially Available Gelatins from Different Sources

Gelatin is used as a functional ingredient in many foods, pharmaceuticals, and cosmetics as a stabilizing, thickening, and gelling agent. The rheological properties of gelatins are important in the potential functionality of gelatin. This study is designed to determine the rheological properties of gelatin extracted from the skins of silver carp (Hypophthalmichthys molitrix Valenciennes 1844). The extracted gelatin is compared with commercially available gelatins from different sources. The results indicate that the stress-strain relationship of gelatin gels remained in the linear region over a broad range of strains and stresses and gave similar elastic moduli at varying frequency, stress, and strain levels. One exception was a commercial high molecular weight fish skin gelatin that gave a lower elastic modulus indicating that its gel strength was low compared to the other gelatin samples studied. Gel strength varied between 220 and 1230 g while viscosity varied between 4.53 and 6.91 cP among the samples. Melting and gelling temperatures varied between 14.2 and 32.3 degrees C and 3.2 and 25.4 degrees C, respectively. Texture profile analysis was done at 2 deformation levels, 25% and 75%, and the results correlated well with gel strength. The correlations between hardness, cohesiveness, and gumminess and gel strength were 0.98, 0.82, and 0.99, respectively, at 25% deformation but lower at 75% deformation. The results suggest that rheological measurements might be used to quickly estimate gel strength using less material. In addition, the silver carp skin gelatin seemed to be of equal quality to some of the commercial gelatins.