Moisture sorption characteristics of dairy whitener at different temperatures

Abstract

The sorption isotherms describe the equilibrium relationship between water activity (a w ) and moisture content of the food at constant temperatures and pressures. The knowledge of sorption isotherms of a food product is essential for product and process development in solving engineering problem such as equipment design, drying and storage condition selection as well as predicting the shelf life of food. In the present investigation, the fraction of adsorption and desorption isotherms of dairy whitener were drawn at three temperatures viz., 30, 40 and 50 o C. A gravimetric static method was used approximately between 11– 92% relative humidity for sorption isotherms that were found to be typical type II sigmoid shape. The equilibrium moisture content (EMC) for dairy whitener within the range of 0.113 to 0.923 was higher at 30 o C as compared to 40 and 50 o C. At the temperatures of 30, 40 and 50 o C, the equilibrium moisture content of dairy whitener increased from 2.837 to 47.263, 2.646 to 28.48 and 2.222 to 17.423 g/ 100 g solids respectively. Experimental data were fitted to five mathematical models viz. Modified Mizrahi, Caurie, Oswin, Halsey and Guggenheim–Anderson–de Boer (GAB). It was found that GAB model was acceptable in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships over the entire range of selected temperatures. Monolayer moisture content of dairy whitener decreased with increasing temperature from 3.355 at 30 o C to 2.199 g/100 g of solids at 50 o C.