2009 年 34 巻 3 号 p. 473-476
Phase transition behavior of sorbed water in Konjac glucomannan (KM)-water systems with various molar mass was investigated using differential scanning calorimetry (DSC). The measurements were performed repeatedly for 3 cycles. In KM-water systems, non-freezing water (Wnf), four types of freezing bound water (Wfb) and free water (Wf) were identified. The Wfb appeared at increasing water content (Wc) in the order; Wfb1, Wfb2, Wfb2* and Wfb3. The proportion of each type of Wfb changed with increasing Wc. Wfb1, Wfb2, and Wfb2* transferred to Wf in high Wc region, but Wfb3 still kept interaction with KM chains. The same types of sorbed water existed in KM with lower molar mass. The amount of Wnf decreased with decreasing molar mass at high Wc, in particular for KM with molar mass less than 2.0×105 Da. The Wfb in KM matrix with high molar mass is strongly influenced by surrounding KM chains, that is to say the water binding ability decreases with decreasing molar mass.