Thermal Behavior of Bio-related Material Gel in Low Water Content

Abstract

We have already reported that the transition behavior of NIPA (700mM) gel is complicated in low water contents (w c ) ranging from 0.01 to 1.7. The thermogram shows a glass transition, an endothermic peak around 34 o C and peaks related to the melting and recrystallization of water. In the present study, the sol-gel transition behavior of egg-white in low water contents (w c = 0.1-1.8) was studied by differential scanning calorimetry. Moreover, the thermal behavior of the gels were intensively studied. In a sol-gel transition process, three endothermic peaks were observed. The peak temperatures are increased as the water content w c is reduced (w c < 1). The thermal behavior of egg-white gel showed complicated behavior similar to the NIPA gel. Amount of free water (which is frozen at 0 o C) in the gel is estimated from the thermogram.

Thermal Behavior of Albumin Gel in Low Water Content

“…This gap is ascribable to the vitrification bound water and network of albumin. We have already reported the heat of fusion of water in egg-white gels as shown in figure 6(b) [13]. In this case, the free water disappears at w c = 0.4, above w c = 0.4, the amount of free water increases linearly up to w c = 0.9 and then above w c = 0.9, the heat of fusion increases parallel to solid line.…”

“…This seems to be due to a changing denaturing mechanism of the albumin greatly with very high concentration below w c = 0.64. In the egg-white sol, three endothermic peaks were observed in the sol-gel transition process [13]. Here, the peak e of the albumin roughly corresponds to the endothermic peak of the high temperature side of the egg-white.…”

“…The solid line is the theoretical line of the heat of fusion change when it is assumed that all the water in the sample freezes around 0 o C into normal ice. [13].…”

“…The w c dependence of the heat capacity gap (■) temperature, the endothermic peaks (○, ◇) temperatures and exothermic peak (▲) temperature obtained from the DSC thermograms in the heating process. [13]. subjected to the heating-cooling-heating cycle.…”

“…1) [13]. The results were compared with those of synthesized gel such as NIPA to examine universality of the appearance of complicated thermal behavior in low water content.…”