Physical properties of food hydrogels on the viewpoint of water state

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In the field of food technology, the gels are not only foods themselves but also best models for investigation of altering the state of disperse system. The transform of polymer suspension through sol to gel state is not governed by chemical change but introduced by physical phenomena. Therefore, the molecular motion of water should be considered as the driving force to form the gel, because water is occupied in gel at large volume. Hence, the coefficients of physical properties of suspensions with polysaccharides, starch and protein during gelation were tried to determine. The results obtained in the present study are as follows ;1) For the measurement of dielectric relaxation of water in the gels, an experimental electrode for liquid sample was made and it was found that the dielectric relaxation was shifted to longer time side when the low molecular weight compounds such as sugar, which has structure-making effects of water, were dissolved in. the solvent. 2) The mechanical gel point for sol-gel transition of agar gels during cooling and starch during heating were determined by Fourier transform Rheometry. 3) T o prevent a slippage of gels which possesses a syneresis, a normal force was applied and obtained the exact yiacoelastic parameters. 4) Although it was impossible to determine the sol-gel transition point of heatinduced gelation of proteins, but we successfully obtained the exact values. 5) The mechanical properties of gels during gelation show the good correspondence with thermal properties such as DSC and thermal diffusivity. 6) The compounds contributed to make a water structure prevent a syneresis and the water release from the gels was obeyed by Pick's diffusion equation but the taste intensity was controlled by the network density of gels.