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This study investigated the thermodynamic properties of water sorption in soybean using the DM 68I69 Ipro variety from Campo Verde, Mato Grosso, Brazil. Grains with initial moisture contents of 21.95% (w.b.) and 3.50% (w.b.) were used for desorption and adsorption analyses, respectively. The static-gravimetric method determined equilibrium moisture content at various temperatures (10, 20, 30, 40, and 50°C) and relative humidity (between 0.11 and 0.92 ± 2%). The Modified Halsey model quantified the hygroscopicity of soybean. Key findings include: (a) desorption equilibrium moisture content exceeded adsorption values, demonstrating hysteresis; (b) decreasing equilibrium moisture content increased the energy required for water removal and its release during adsorption; (c) differential entropy of desorption and adsorption increased with decreasing equilibrium moisture content; (d) Gibbs free energy decreased with increasing temperature for both desorption and adsorption. The enthalpy-entropy compensation theory effectively described the observed phenomena.

Knowledge of the relationship between the equilibrium moisture content of the product and the air that involves it is essential to guarantee product quality and preserve its characteristics during storage. This trend can be studied by sorption isotherms. Thus, this study aimed to obtain desorption and adsorption isotherms of soybean grains to determine the mathematical model that best fits the experimental data and analyze the hysteresis phenomenon. Soybean grains with a moisture content of 21.95% (db) were used to verify the desorption process. The grains were dried until 3.50% (db) for the adsorption process. The static-gravimetric method was employed to determine the equilibrium moisture content of the grain at different temperatures (10, 20, 30, 40, and 50°C) and relative humidity levels (0.10 to 0.92%). Eight mathematical models were fitted to the experimental data. The modified Halsey model satisfactorily represented the desorption and adsorption phenomena of soybean grains. The equilibrium moisture content of soybean grains increased along with an increment in water activity. The increase in temperature led to a reduction in the equilibrium moisture content of soybean grains at a constant water activity. The equilibrium moisture content values obtained by desorption are higher than those obtained by adsorption, indicating the hysteresis phenomenon at the studied temperature range. The isotherms obtained for the desorption and adsorption process were classified as type III because of the high oil content in soybean grains.

The powdered products industry demands certain parameters for the transport of these products, such as flowability. This has a direct impact on actions within the industry and in machinery development. For Coffea canephora, this information is absent in the relevant literature. Thus, the present study aimed to analyze alterations in the flow properties of Coffea canephora due to the degree of roasting, particle size, and storage temperature. Two degrees of roasting were used: medium light (ML) and moderately dark (MD). Later, the coffee was divided into four particle size categories: whole roasted coffee and coffee ground to fine, medium, and coarse sizes. These lots were kept at 10 °C and 30 °C and the flowability parameters were studied throughout the storage period (0, 30, 60, 120, and 180 days). The angle of internal friction presented higher values for higher degrees of roasting and lower values for larger particle sizes. The MD and fine coffee samples presented higher values for the wall friction angle. Steel provided the lowest values for the wall friction angle. Unground roasted coffee was classified as free-flowing, whilst coffee with a coarse or fine particle size was classified as having an easy flow and a cohesive flow, respectively. According to the K coefficient, coffee roasted to MD required storage containers that were more robust, such as having thicker silo walls or being constructed of a material with a higher resistance, to prevent the storage container from collapsing during transport.

This study aimed to obtain the drying and water absorption curves of husk rice grain (Oryza sativa L.), cv. Urucuia, as well as the thermodynamic properties. Five temperatures (35°C, 45°C, 55°C, 65°C and 75°C) were used. Two terms, logarithmic, modified Midilli, Page and Verma models were used to model the drying process, and the Peleg model was used to model the soaking process. The modified Midilli and Peleg models satisfactorily accounted for the processes of drying and absorption of water, respectively. The activation energy for the drying and soaking was 51.03 and 37.06 kJ mol −1 , respectively. The enthalpy and entropy decreased with increasing temperature, regardless of the process. Their values ranged between −6.60 and 48.47 kJ mol −1 and between −0.1084 and −0.2464 kJ mol −1 K −1 for enthalpy and entropy, respectively. The Gibbs free energy increased with increasing temperature, with values between 69.36 and 86.22 kJ mol −1 .

ABSTRACT The aim of this study was to model and determine the thermodynamic properties of moisture sorption in soursop fruit powder. The isotherms were determined by the static method at temperatures of 10, 20, 30, 40 and 50 °C, and a water activity of between 0.113 and 0.868 (decimal). The GAB model effectively described the moisture sorption phenomenon of soursop powder. The monolayer moisture content ranged from 12.589 to 9.109% db. The enthalpy values related to the GAB model were negative, with -2581.035 kJ kg-1 for C0 and -107,758 kJ kg-1 for K0. The isosteric heat of sorption, entropy and Gibbs free energy had a high correlation with the equilibrium moisture content, and the correlation between enthalpy and entropy was confirmed for moisture sorption in soursop powder.

A escoabilidade dos produtos agrícolas é importante fator a ser considerado na pós-colheita, impactando diretamente no número de operações e no dimensionamento de maquinários. Assim, objetivou-se avaliar e determinar o coeficiente K e as propriedades de fluxo de grãos de café em função de diferentes níveis de torra, granulometria, temperatura e tempo de armazenamento. Grãos de café foram torrados nos níveis média clara e moderadamente escura, e depois moídos nas granulometrias fina, média e grossa. Um lote adicional de grãos de café não foi moído. As amostras foram armazenadas a 10 °C e 30 °C e analisadas durante o armazenamento (0, 30, 60, 120 e 180 dias) em relação aos parámetros: coeficientes interno e externo de atrito, ângulo de atrito interno, ángulo de atrito interno efetivo, ângulo de atrito com a parede (concreto, aço e madeira) e o coeficiente de pressão lateral (coeficiente K). O ângulo de atrito interno variou significativamente com a granulometria e o nível de torra. A torra moderadamente escura e a granulometria fina obtiveram maiores valores (ao redor de 29,5 °) de ângulo de atrito com a parede. Quanto ao material em que as amostras foram colocadas, a madeira foi o material no qual as amostras apresentaram os maiores valores de ângulo de atrito com a parede, seguidas pelas amostras colocadas no concreto e no aço, quando comparadas na mesma temperatura de armazenamento, no mesmo nível de torra e na mesma granulometria. Os grãos de café inteiros foram classificados como de fluxo livre. A granulometria fina levou a um fluxo coesivo, de acordo com a função fluxo. Café torrado em média clara, inteiro, requer estruturas de armazenagem que suportem maior pressão, de acordo com os valores do coeficiente K.

Hygroscopic equilibrium curves or sorption isotherms are important in order to define dehydration limits of the product, estimate moisture content alterations under environment conditions and to acquire moisture content values for safe storage. This work aimed to determine desorption isotherms of cucumber seeds stored at different temperature (10, 20, 30, 40 and 50 ºC) and relative humidity (0.11 to 0.96) and the thermodynamic properties of this process. Mathematical models were fitted to experimental data in order to represent the agricultural products hygroscopicity. Net isosteric heat of desorption was performed based on the Clausius-Clapeyron thermodynamic relation and Gibbs free energy through the Van't Hoff equation. Based on statistical parameters, Modified Henderson model was the one that best represented hygroscopicity of cucumber seeds. Equilibrium moisture content of cucumber seeds decreased with temperature increment at a constant value of relative humidity. Differential enthalpy values, representing the energy required to remove moisture from the cucumber seeds, ranged from 2923 to 2469 kJ. kg-1. Values of differential entropy and Gibbs free energy decreased with moisture content increase. Enthalpy-entropy compensation theory is valid for the sorption of cucumber seeds, in which the water sorption mechanism in cucumber seeds can be considered to be enthalpy controlled.

The objective of this research was to determine the mechanical properties of beans (BRSMG Majestuoso) coated with carnauba wax solution. Grains with 0.1481 (d.b.) moisture content was used. Treatments 0, 1 and 2 were respectively defined as the control sample, application of the wax diluted 1/1 (carnauba wax solution/water) and application of carnauba wax without dilution. Uniaxial compression tests were performed in the universal test apparatus, TA HD Texture Analyzer with 500 N load cell. Compression tests were carried out during the storage period of in-nature grains, in those that underwent the hydration process at 40 and 50 °C of temperature and in grains during the cooking process. Only the storage time had a significant effect (P<0.05) on the rupture force and the proportional deformity module. Hydration and cooking of the grains provided a reduction in the values of the studied variables. RESUMO: Objetivou-se com este trabalho determinar as propriedades mecânicas de grãos de feijão cultivar BRSMG Majestoso revestidos com cera de carnaúba. Foram utilizados grãos com teor de água de aproximadamente 0,1481 decimal b.s. (base seca), tratados com solução de cera de carnaúba. Parte destes destinou-se à amostra testemunha, uma a aplicação de cera diluída na proporção de 1/1 (solução de cera de carnaúba/água) e outra a aplicação apenas de solução de cera de carnaúba, tratamentos 0, 1 e 2, respectivamente. Foram realizados ensaios de compressão uniaxiais no aparelho universal de testes, TA. HD Texture Analyser, com célula de carga de 500 N. Os testes de compressão foram realizados ao longo do período de armazenamento nos grãos in natura, naqueles que passaram pelo processo de hidratação nas temperaturas de 40 e 50 °C e em grãos ao longo do processo de cocção. Apenas o tempo de armazenamento teve um efeito significativo (P<0,05) sobre a força de ruptura e o módulo proporcional de deformidade. A hidratação e a cocção dos grãos proporcionaram redução nos valores das variáveis estudadas.

The objective of this study was to model the kinetics of water sorption in roasted and ground coffee. Crude Arabica coffee beans with an initial moisture content of 0.1234 kgwkgdm-1 were used. These beans were roasted to a medium roast level (SCCA # 55) and ground at three particle sizes: coarse (1.19 mm), medium (0.84 mm) and fine (0.59 mm). To obtain the water sorption isotherms and the isosteric heat, different conditions of temperature and relative humidity were analyzed using the dynamic method at 25ºC (0.50, 0.60, 0.70, and 0.80 of RH) and 30°C (0.30, 0.40, 0.50, 0.60, 0.70, and 0.80 of RH) and using the static method at 25ºC (0.332 and 0.438 of RH). The GAB model best represented the hygroscopic equilibrium of roasted coffee at every particle size. Isosteric heat of sorption for the fine particle size increased with increments of equilibrium moisture content, indicating a strong bond energy between water molecules and the product components. The Gibbs free energy decreased with the increase in equilibrium moisture content and with temperature.

This study aimed to verify the influence of moisture content on the values of maximum compressive strength, proportional deformity modulus, elastic coefficients d, e, and f beyond the tangent values, and maximum grain drying of crambe (Crambe abyssinica Hochst) under compression in natural resting position. Crambe grains with moisture contents ranging from 0.1547 to 0.0482 decimal db were dried at 40°C and uniaxially compressed between two parallel plates in the natural rest position. The gravimetric method was used to monitor reduction in moisture content during drying (weight loss). It was concluded that the compression force required to deform the crambe grains decreases as the moisture content increases. The proportional deformity modulus increases as the deformation decreases, yielding values between (0.09-0.27)×102MPa. Sigmoidal model described by Taylor series adequately represents the compression resistance of crambe grains in the natural rest position with moisture content lower than 0.0813db. RESUMO: Neste trabalho objetivou-se verificar a influência do teor de água nos valores da força máxima de compressão, módulo proporcional de deformidade, coeficientes elásticos d, e, f, além dos valores da tangente e secante máximas nos grãos de crambe (Crambe abyssinica Hochst), submetidos à compressão na posição natural de repouso. Os grãos de crambe, utilizados com teores de água entre 0,1547 e 0,0482 (decimal b.s.), foram secos nas temperaturas de 40°C e comprimidos uniaxialmente entre duas placas paralelas, na posição natural de repouso, cuja redução do teor de água ao longo da secagem foi acompanhada pelo método gravimétrico (perda de massa). A força de compressão necessária para deformar os grãos de crambe diminui com o aumento do teor de água. O módulo proporcional de deformidade aumenta com a redução da deformação, obtendo-se valores entre 0,09 e 0,27 (x 102MPa), em que o modelo sigmoidal, descrito por meio da série de Taylor, representa adequadamente a resistência dos grãos de crambe à compressão na posição natural de repouso, para os teores de água menores que 0,0813 (b.s.)