Moisture Adsorption Characteristics of Sandesh Powder

Abstract

Sorption studies were carried out for sandesh  powder  at  10,  20  and  40^oC to  determine its   moisture adsorption characteristics. The adsorption curves obtained were observed to follow a sigmoid shape and corresponds to type II, with a definite inversion due to the temperature effect above 0.79 water activity. The GAB, BET and Caurie isotherm models were attempted to describe the experimental data and were found to give the best fit between experimental and predicted values as indicated by R² values. Monolayer moisture content was calculated using the BET and GAB model. Caurie model was used to compute the properties of sorbed water viz., monolayer water, number of adsorbed monolayer, density, and surface area of adsorption in sandesh powder. The net isosteric heat of sorption of water in sandesh powder estimated using Clausius-Clapeyron equation at different moisture contents indicated its strong dependence on moisture content.