Sorption Isotherms and Moisture Diffusivity in Fried Cassava-Shrimp Chips

Equilibrium moisture sorption isotherms of fried cassava-shrimp chips were investigated by measuring water activity at 20, 30, and 40°C for modeling transient diffusion of moisture. The sorption isotherms followed a type III shape in water activity range of 0.1–0.9 showing negligible influence of temperature, and were best represented by the GAB, Henderson, and modified Henderson equations. Effective moisture diffusivity of chips based on analytical solution of Fick's law ranged from 0.8 × 10−11 to 2.1 × 10−10 m2/s during exposure to fixed relative humidity (50, 70, and 90%) and temperature (20, 30, and 40°C) environments. An Arrhenius type relationship adequately described the dependence of effective moisture diffusivity both on temperature and relative humidity, and led to good agreement between experimental and estimated transient moisture sorption data.