The sorption isotherms of dudh churpi, a shelf-stable traditional milk product in India, determined at 15, 25, 35 and 45 degrees C, were typical type II sigmoidal according to the BDDT (Brunauer-Deming-Deming-Teller) classification. Nine equations, namely Bradley, Henderson, Iglesias and Chirife, Khun, Mizrahi, GAB (Guggenheim-Anderson-de Boer), modified Mizrahi, Oswin and Caurie were fitted to the sorption data. Caurie's equation was found to be suited best to predict equilibrium moisture content of dudh churpi. Monolayer value, density of sorbed water, number of monolayers and area of adsorbent decreased with the increase in temperature.

Moisture sorption characteristics of wadi, a condiment in the Indian Subcontinent, were investigated at temperature of 15-45°C and water activities (a w ) of 0.11-0.97. The sorption isotherms were sigmoidal. Nine different mathematical models were found to effectively describe the moisture sorption data on the basis of regression analyses and goodness of fit. Each model was statistically evaluated by means of percent root mean square and coefficient of determination. The GAB model gave the best fit in the entire range of a w . Temperature dependence of the GAB constants and good fit were determined. Using the Caurie's model, the properties of sorbed water, such as monolayer moisture content, number of adsorbed monolayers, density of sorbed water, bound water content and surface area of adsorption, which decreased with an increase in temperature, were calculated. The monolayer moisture content ranged from 102.7 to 128.7 g/kg solids in wadi. The optimum storage temperature and a w for wadi were 15-25°C and <0.7, respectively.

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