Adsorption of moisture on dried juniper berries (Juniperus communis L.) at various temperatures and properties of sorbed water
2008
Červenka, L., University of Pardubice, Pardubice (Czech Republic)
Moisture adsorption characteristics of juniper berries were studied using Brunauer-Emmet-Teller (BET), Guggenheim-Anderson-de Boer (GAB) and Peleg sorption equations. A reasonable goodness of fit to the experimental data over the entire range of water activity was obtained with the GAB equation. A negative temperature effect was observed, particularly at the curves measured at 10 deg C. The monolayer moisture contents decreased with an increase in temperature of adsorption using the GAB model. Cauries equation was used to obtain data on non-freezing water, surface area of sorption, density of the sorbed water and the number of adsorbed monolayers. Values of these parameters decreased with an increase in the temperature. The linear form of Henderson isotherms intersected at moisture contents ranged from 158.5 g per kg to 114.8 g per kg (on dry weight basis) representing the transition from multilayer sorbed water to mobile water. Dehydrated juniper berries kept at ambient temperature would require less hydration to be enzymatically active (i.e. above 0.40 a sub(w)). Isosteric heat of adsorption obtained by applying Clausius-Clapeyron equation decreased exponentially with the increasing moisture contents. Results showed that the refrigerated storage of dry juniper berries may be beneficial to preserve their nutritional value.
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