Ikeda S, Nishinari K
Department of Food and Nutrition, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
J Agric Food Chem. 2001 Sep;49(9):4436-41. doi: 10.1021/jf0103065.
The rheological properties of kappa-carrageenan helices dispersed in an aqueous medium, which prevents aggregation of helices, were investigated. A dispersion of 1.5% w/w nonaggregated kappa-carrageenan helices exhibited gel-like dynamic mechanical spectra at 20 degrees C; that is, the storage modulus G' predominated over the loss modulus G' ' in the entire frequency range examined (0.5-100 rad/s). However, the observed slight frequency dependence of the moduli and the relatively large value of tan delta (= G' '/G' > 0.1) were typical of so-called weak gels. The magnitude of G' of the kappa-carrageenan weak gels was less than that of conventional gels formed by 0.15% w/w kappa-carrageenan in an aggregating condition at 20 degrees C. Under large deformation, enough for the conventional gels to rupture, the weak gel systems flowed but never ruptured, suggesting that the weak gel-type rheological properties of the kappa-carrageenan dispersions were due to a sufficiently long relaxation time of topological entanglements among double-helical conformers but not due to the formation of a three-dimensionally percolated permanent network.
研究了分散于水介质中的κ-卡拉胶螺旋体的流变特性，该水介质可防止螺旋体聚集。1.5% w/w的非聚集κ-卡拉胶螺旋体分散体在20℃下呈现出类凝胶状的动态力学谱；也就是说，在所考察的整个频率范围（0.5 - 100 rad/s）内，储能模量G' 大于损耗模量G'' 。然而，观察到的模量的轻微频率依赖性以及相对较大的tanδ值（= G'' /G' > 0.1）是所谓弱凝胶的典型特征。κ-卡拉胶弱凝胶的G' 大小小于由0.15% w/w κ-卡拉胶在20℃聚集条件下形成的传统凝胶的G' 。在大变形下，大到足以使传统凝胶破裂，弱凝胶体系流动但从不破裂，这表明κ-卡拉胶分散体的弱凝胶型流变特性是由于双螺旋构象体之间拓扑缠结的足够长的弛豫时间，而不是由于三维渗透永久网络的形成。
