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The effects of sucrose syrup concentration (40-70 g/100-g solution) and temperature (40-90C) on water loss and sucrose uptake by mango mesocarp slices during osmotic dehydration were investigated. The effective diffusivities for mass transfer were determined using the slope method based on the Fickian diffusion model. Water loss and sucrose uptake were proportional to the square root of osmotic contact time, implying that the process is Fickian. The specific mass transfer rate constants and effective diffusivities (D e ), derived from Fick's unsteady-state diffusion equation, increased with temperature and sucrose syrup concentration. D e values for water loss and sucrose uptake, which ranged between 2.59 ¥ 10 -6 to 5.12 ¥ 10 -6 m 2 /h and 1.70 ¥ 10 -6 to 4.14 ¥ 10 -6 m 2 /h, respectively, were related to absolute temperature using an Arrhenius-type relationship. The activation energies, which fell in the range previously reported for diffusion-controlled processes, increased with sucrose syrup concentration and varied from 9.74 to15.16 KJ/mol. 3 Corresponding

The effect of temperature and relative humidity on the water vapour permeability (WVP) and mechanical properties of cassava starch and soy protein concentrate (SPC) based edible films containing 20 % glycerol level were studied. Tensile strength and elastic modulus of edible films increased with increase in temperature and decreased with increase in relative humidity, while elongation at break decreased. Water vapour permeability of the films increased (2.6-4.3 g.mm/m(2).day.kPa) with increase in temperature and relative humidity. The temperature dependence of water vapour permeation of cassava starch-soy protein concentrate films followed Arrhenius relationship. Activation energy (Ea) of water vapour permeation of cassava starch-soy protein concentrate edible films ranged from 1.9 to 5.3 kJ/mol (R (2)  ≥ 0.93) and increased with increase in SPC addition. The Ea values were lower for the bio-films than for polyvinylidene chloride, polypropylene and polyethylene which are an indication of low water vapour permeability of the developed biofilms compared to those synthetic films.

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ResumoAs características da adsorção de umidade de amostras de gengibre secas foram estudadas para se determinar o efeito das condições de armazenamento com o propósito de se prever a vida de prateleira ou validade, a seleção de materiais apropriados para empacotamento, avaliar a bondade de ajuste dos modelos de sorção e determinar a termodinâmica da adsorção de umidade para aplicação em secagem. Houve um efeito significativo (p ≤ 0,05) da atividade de água, da temperatura e do pré-tratamento sobre o teor de umidade de equilíbrio higroscópico das amostras de gengibre secas. Sob atividade de água constante (a w ), o teor de umidade de equilíbrio higroscópico (CEM) diminuiu com o aumento da temperatura. O teor de umidade de equilíbrio higroscópico de todas as amostras aumentou com o aumento da atividade de água, sob temperatura constante. A umidade de sorção das amostras de gengibre com casca foi maior do que a das amostras de gengibre sem casca enquanto que a das amostras de gengibre não escaldo com e sem casca foi maior do que a das amostras de gengibre escaldado com e sem casca. A equação de Henderson permite previsões mais exatas das isotermas com o menor valor de média quadrática percentual (%RMS) e, portanto, descreve melhor os dados de adsorção dos modelos de Guggenheim Anderson De-Boer (GAB), Oswin e Halsey, nesta ordem. A umidade de monocamada, em geral, diminuiu com a temperatura em todas as amostras. O calor isostérico diminuiu quando o teor de umidade se aproximou do valor assimptótico ou o calor latente de vaporização da água pura (∆H st = 0), enquanto que a entropia de sorção aumentou com o teor de umidade. Palavras-chave: modelos de sorção; termodinâmica; atividade de água; amostras de gengibre. AbstractThe moisture adsorption characteristics of dried ginger slices was studied to determine the effect of storage conditions on moisture adsorption for the purpose of shelf life prediction, selection of appropriate packaging materials, evaluate the goodness-of-fit of sorption models, and determine the thermodynamics of moisture adsorption for application in drying. There was a highly significant effect (p ≤ 0.05) of water activity (a w ), temperature, and pre-treatment on the equilibrium moisture content (EMC) of the dried ginger slices. At constant a w , the EMC decreased as temperature increased. The EMC of all samples increased as the a w increased at constant temperature. The sorbed moisture of the unpeeled ginger slices was higher than the peeled while those of unblanched samples were higher than the blanched. Henderson equation allows more accurate predictions about the isotherms with the lowest %RMS, and therefore, it describes best the adsorption data followed by GAB, Oswin, and Halsey models in that order. The monolayer moisture generally decreased with temperature for all samples. The isosteric heat decreased with moisture content approaching the asymptotic value or the latent heat of vaporization of pure water (∆H st = 0) while the entropy of sorption was observed to increase with moisture con...