Ecology, Environment and Conservation Paper

Vol 22, Sept. Suppl. Issue , 2016; Page No.(235-241)

STUDY ON MOISTURE DESORPTION CHARACTERISTICS AND ISOSTERIC HEAT OF DAIRY WHITENER

Bhavesh B. Chavhan, C. Sahu, A.K. Agrawal and R.K. Sahu

Abstract

In the present experiment, we studied the moisture desorption behavior and heat of desorption of dairy whitener at three different temperatures viz., 30, 40 and 50°C. A static gravimetric method was used under 0.11 – 0.92 water activity ranges for the determination of sorption isotherms that were found to be typical type II sigmoid. Experimental data were fitted to five mathematical models viz. Modified Mizrahi, Caurie, Oswin, Halsey and Guggenheim–Anderson–de Boer (GAB). Out of these five models, the GAB model was found to be most acceptable in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships for dairy whitener over the entire range of temperatures. The equilibrium moisture content of dairy whitener samples was found to be reduced at higher temperature at the same water activity (aw). Similarly, at the same temperature, the equilibrium moisture content has increased with increase in water activity. The monolayer moisture in desorption deceased from 4.773 to 4.329 g/100 g solids with increase in temperature from 30 to 50oC. The net isosteric heat of desorption decreased exponentially with increase in moisture content. The isosteric heat of desorption for dairy whitener ranged from 18.977 kJ/mol at 5% moisture content (d.b.) to 2.219 kJ/mol at 30 % (d.b.) moisture content.

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