Moisture sorption characteristics of Rasomalai at different temperatures

The sorption characteristics of rasomalai were measured at the temperatures of 20C, 30C, and 40C and found to be in the water activity range of 0.11 0.97. The isotherm exhibit sigmoid shape and correspond to type II. In rasomalai, at all water activities values of equilibrium moisture content decreased with an increase in storage temperature. However, a clear cut inversion was observed intermittently at 30C and 40C. The BET and GAB equation fitted hold good as indicated by the statistical values R, P, %RMS & chi square. The BET monolayer value in rasomalai decreased from 5.11g of water/100g of solids at 20C to 3.80 g of water/100 g of solids at 40C. The GAB monolayer value for rasomalai decreased from 5.04 g of water/ 100 g of solids at 20C to 3.86 g of water/100 g of solids at 40C. The Caurie equation was used to determine properties of sorbed water viz., density of sorbed water, number of adsorbed monolayers, bound or non freezabe water and surface area of sorption in rasomalai. The net isosteric heat of sorption in rasomalai ranged from 58.24 kJ/mol at 6.63 % moisture content to 0.44 kJ/mol at 32.75 % moisture content.