Equilibrium Sorption Isotherms and Isosteric Heat of Rose Hip Fruits (Rosa Eglanteria)

Abstract

For sorptional data to be useful in simulation and design purposes, they must be represented by equations valid in the conditions usually found in industrial practice. In this regard sorptional models that include the influence of temperature on desorption and sorption equilibrium values are most valuable. In this article, water desorption and sorption isotherms of rose hip fruits (Rosa Eglanteria) were experimentally determined by the gravimetric method, and from these the isosteric heat of sorption was calculated. According to the ANOVA test carried out for this fruits, no significant differences were found between experimental desorption and adsorption isotherms. Seven models were tested to mathematically represent the moisture content as a function of water activity (aw) in the aw range of 0.11 to 0.85 and temperatures of 20, 40, and 60°C, for further use in process simulation. The five-parameter GAB model was most accurate, with an MRE of −2,9 % and R2 = 0.989. The values obtained for the isosteric heat of sorption were fitted with a previous published equation, with an MRE% = −0.05. The isosteric heat of sorption derived from the GAB five parameters equation, for the corresponding monolayer moisture content, only differed by 1.25% with the calculated in this paper.