Heat of sorption of water in dried fruits

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Abstract
Summary: The heats of moisture adsorption and desorption in four dried fruits (sultana raisins, figs, prunes and apricots) were estimated from equilibrium sorption data, using the Clausius‐Clapeyron equation in the temperature range 15–60°C. The net isosteric heat of sorption (qst) decreased sharply from about 20 kJ mol−1 water to near zero when the moisture content was increased from 0.05 to 0.50kg water kg−1 dry matter. An exponential function was fitted to the experimental qst values at various moisture contents (X), yielding two characteristic constants (q0 and X0) for each fruit. Mean and total heats of sorption were calculated from the proposed empirical equation, which are useful for enthalpy prediction in food dehydration. The heats of desorption were higher than the heats of adsorption, indicating significant hysteresis in the sorption of water, especially in dried apricots.