The equilibrium moisture content for adsorption and desorption isotherms of mango skin was determined using the static gravimetric method at temperatures of 20, 26, 33, 38 and 44 o C in the 0.056 to 0.873 water activity range. Both sorption curves show a decrease in equilibrium moisture content as the temperature increasing. The hysteresis effect was observed at constant water activity. The Guggenheim, Anderson, and de Boer (GAB) model presented the best fitting accuracy among a group of models and was used to determine the thermodynamic properties of water sorption. Integral enthalpy and integral entropy areas showed inverted values for the adsorption and desorption isotherms over the wide range of water activity studied. These values confirm, in energetic terms, the difference between adsorption and desorption isotherms observed in the hysteresis phenomenon. Finally, the Gibbs free energy revealed that the sorption process was spontaneous for both sorption isotherms.Keywords: agricultural waste; gravimetric method; integral properties; modelling; water content.Practical Application: This work presents information about the hysteresis characteristics of mango skin as well as their thermodynamic properties of water sorption. The information given in this study can be used for processing, storage, and packaging of this agro-waste. In addition, the combination of classical and modern methodologies is useful for determining the best stability conditions over a range of water activity and equilibrium moisture content.

Orange peels are a promising agroindustry-waste that can be implemented in the extraction and production of pectin, as dietary fiber in food formulations, and as a biopolymer for metal adsorption in water treatment. The present work, therefore, aims to study the adsorption isotherms and the thermodynamic properties of the water adsorbed from orange peels (C. sinensis cv. Brazilians) at six different temperatures (20, 30, 40, 50, 60 and 70 °C) in the water activity range of 0.020 to 0.853. The GAB model was applied in modeling the experimental adsorption isotherms of orange peels, obtaining statistical values of R 2 = 0.996. Differential and integral thermodynamic properties of water sorption for orange peels were determined by the analytical derivation of the water activity with respect to the temperature from GAB model. Results of the differential thermodynamic properties showed an energetic interaction zone of water molecules with the material. Furthermore, integral thermodynamic properties showed an equilibrium zone controlled by the orange peel enthalpy and entropy. Finally, the orange peel power adsorption information can be used as a point of reference for the controlled process in the different application areas. RESUMO -As cascas de laranja são resíduos importantes da agroindústria que podem ser empregados na extração e produção de pectina, produção de fibra, em formulações de alimentos e como um biopolímero em processos de adsorção de metais no tratamento de águas. Assim, o objetivo deste trabalho foi estudar as isotermas de adsorção de casca de laranja (Citrus sinensis cv. Brasileira) a seis diferentes temperaturas (20, 30, 40, 50, 60 e 70 ° C) na faixa de atividade de agua de 0.020 até 0.853. Para isto, o modelo teórico de GAB foi usado para modelar as isotermas experimentais de adsorção da casca de laranja, mostrando valores estadísticos de R 2 = 0.996. Propriedades termodinâmicas diferenciais e integrais de sorção da água na casca de laranja foram determinadas através da derivada analítica da atividade de água com respeito à temperatura proveniente do modelo de GAB. Os resultados das propriedades termodinâmicas diferenciais mostraram uma área de interação energética das moléculas de água com o material. Além disso, as propriedades termodinâmicas integrais mostraram uma área de equilíbrio controlado pela entalpia e entropia para a casca de laranja. Finalmente, a informação sobre o poder de adsorção de casca de laranja pode ser usada como ponto de referência no controle de processos para as diferentes áreas de aplicação.Palavras-chave: agroresíduos; derivação analítica; modelo de GAB; modelagem; conteúdo de água.

Determinou-se a atividade antimicrobiana "in vitro" de quatro óleos essenciais de condimentos e especiarias (canela, cravo, gengibre e menta), em três diferentes concentrações (10,0; 1,0 e 0,1%) sobre vinte e um microrganismos (sete leveduras e quatorze bactérias). Para tanto, foram utilizados inóculos padronizados destas leveduras e bactérias, previamente crescidos em caldo nutriente e semeados pela técnica de plaqueamento em réplica, em placas de Petri contendo ágar nutriente + tween 20, sem tratamento (controle) e com as diferentes concentrações dos óleos essenciais estudados. Os resultados, obtidos após incubação a 30 °C por 30 dias, demonstraram que, dentro dos parâmetros utilizados no experimento, os óleos essenciais com maior atividade antimicrobiana foram os de canela e menta, nas concentrações de 10,0 e 1,0%. O óleo de cravo também inibiu completamente o crescimento de todos os microrganismos testados na concentração de 10,0%.

Passion fruit seeds are an important by-product of the juice industry. In this study, physical, thermal and water-sorption properties of passion fruit (Passiflora edulis Sims f. flavicarpa Degener) seeds were determined. The knowledge of such properties is useful to design equipment or operations for storage or processing purposes. The physical properties of bulk density, particle density and bulk porosity, and the thermal properties of conductivity, diffusivity and specific heat were determined between water and mass fractions of 0.126 and 0.493. The thermal properties were determined for packed beds of seeds (effective properties), by means of which the thermal properties of the seeds (particle properties) were estimated. Different empirical models were evaluated for modeling the physical and thermal properties as function of moisture content. Physical and thermal properties were successfully described by a second-order polynomial, except by the specific heat which was described by a second-order logarithmic relationship. The isosteric heat, the differential entropy and the Gibbs free energy of water sorption were estimated using the Henderson model, which best fitted the experimental desorption isotherms at temperatures between 30°C and 70°C and relative humidities between 2% and 90%.