Water Sorption Kinetics of Starch Noodles with Different Cross-Sectional Shapes

摘要

The water sorption process of three types of starch noodles with different cross-sectional shapes is studied in a temperature range of 30 degrees C-70 degrees C. The process could be expressed by a rate equation based on a linear driving-force approximation, for all the noodles and at any temperature. The activation energy for water penetration is practically negligible for all the noodles, indicating that there is no energy barrier for water migration. For two noodles with approximately square and rectangular cross-sections, the equilibrium moisture content shows different degrees of temperature dependence at temperatures higher and lower than the gelatinization temperature of starch. The enthalpy changes for water sorption in the high- and low-temperature regions are greater than 20 kJ mol(-1) and lesser than 10 kJ mol(-1), respectively. It is suggested that the rate-limiting step of water sorption for gluten-free noodles was movement of water through the laminar fluid film on the noodle surface. The validity of this suggestion is confirmed by the fact that the water sorption rate increased as the shaking speed during water sorption increased. These findings indicate that increasing the specific surface area is effective in preparing gluten-free starch noodles with a high water sorption rate.