INFLUENCE OF FLUIDITY OF WATER WITHIN FOOD HYDROGEL ON ITS VISCO-ELASTICITY

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In order to clarify the reason why the visco-elasticity of kamaboko, a sort of entropy elastic body, is decreased with raising temperature is investigated. On raising the temperature of the kamaboko from 0ﾟ to 80ﾟC, its weight was decreased due to the syneresis, and the electric capacity and expressible water were increased, simultaneously, the free water observable by differential IR spectrum was increased. From the results, there arose a now question that the decrease in the visco-elasticity is due to the increase in the fluidity of water.Next, in order to clear this question, the visco-elasticity was measured on the hydrogel models. The first model was a perforated tennis ball filled with various concentrations of polyethylene glycol 600 (PEG), which was designed as a model of syneresis. Upon raising the PEG concentration, the elastic modulus and viscosity of this model obtained by force-deformation measurements were increased. The instantaneous elastic modulus and viscosity obtained by the stress-relaxation and creep measurements were increased. Furthermore, the visco-elasticity was measured on the three hydrogel models of a closed system from which water did not flow out upon their compression. In all the cases, the instantaneous elastic modulus was somewhat increased by the suppression of the fluidity of water, although the viscosity was not always increased. From the results, it is assumed that, upon the deformation of a food hydrogel, water flowed within it, and that its visco-elasticity was also influenced by the fluidity of the water. There may be a possibility that the reason why the visco-elasticity, of the kamaboko is decreased with raising the temperature is due to the increase in the fluidity of water within it.