(2017) Thermodynamic properties of drying process and water absorption of rice grains, CyTA -Journal of Food, 15:2, 204-210, DOI: 10.1080/19476337.2016 To link to this article: https://doi.org/10. 1080/19476337.2016 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 Las propiedades termodinámicas del proceso de secado y absorción de agua de granos de arroz RESUMEN Este estudio pretende obtener las curvas de secado y absorción de agua de las cáscaras de granos de arroz (Oryza sativa L.), cv. Urucuia, así como sus propiedades termodinámicas. Se utilizaron cinco temperaturas (35°C, 45°C, 55°C, 65°C y 75°C). Se utilizaron dos conceptos, logarítmico y modelos Midilli, Page y Verma modificados para modelar el proceso de secado, además se utilizó el modelo Peleg para modelar el proceso de remojo. Los modelos Midilli and Peleg modificados modelaron satisfactoriamente los procesos de secado y absorción de agua, respectivamente. La energía de activación del secado y el remojo fue de 51,03 y 37,06 kJ mol

-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.

A secagem de produtos agrícolas é largamente utilizada no mundo para diminuir o teor de água do produto, dificultando o crescimento microbiano e a ocorrência de reações químicas e bioquímicas e possibilitando a armazenagem segura por períodos longos, além de reduzir o volume e a massa a ser transportada. O objetivo do presente trabalho foi avaliar e modelar a etapa de secagem de morangos (Fragaria L.), bem como obter parâmetros termodinâmicos em três diferentes temperaturas (40 °C, 50 °C e 60 °C). Foram utilizados frutos obtidos na CEASA-DF, com teor de água inicial de 93,0% (b.u. SummaryThe drying of agricultural products is widely used throughout the world to diminish the moisture content of the product, making microbial growth and chemical and biochemical reactions difficult, enabling safe storage for longer periods and also reducing the volume and mass to be transported. The aim of the present work was to evaluate and model the drying process of strawberries (Fragaria L.) and obtain the thermodynamic parameters at three different temperatures (40, 50 and 60°C). Fruits purchased at CEASA-DF with an initial moisture content of 93% (w.b.) were used. The experimental data were fitted to six mathematical models commonly employed to represent the drying step. The activation energy for the drying of strawberries and also the entropy, enthalpy and Gibbs free energy were determined. The Logarithmic model was the one that best fitted the drying phenomenon of strawberry fruits, presenting values for the mean relative error between 7.59 and 8.48%, with an estimated standard error between 0.03 and 0.06 and determination coefficient between 99.93 and 99.95%.

This work aimed to evaluate alterations on the water sorption of coffee due to roast, grind, and storage. Crude grain coffee (Coffea arabica) was roasted at two levels: medium light and moderately dark. Grain was grinded in fine (0.59 mm), medium (0.84 mm), and coarse (1.19 mm) particle sizes, besides the whole coffee lot. Samples were then stored at polypropylene bags and kept at biochemical oxygen demand type chambers in two storage temperatures (10 and 30C). These were analyzed at 0, 30, 60, 120, and 180 days, regarding water content and water activity. Mathematical modeling and thermodynamic properties of coffee moisture adsorption process were accomplished. It was concluded that particle size did not significantly affect water content of coffee, independently of roast degree. Sigma-Copace model best represented hygroscopic equilibrium of roasted coffee. Water content reduction increases the differential enthalpy and entropy of sorption and Gibbs free energy. PRACTICAL APPLICATIONSCommercialization of crude grain coffee, soluble coffee, roasted, and grinded coffee, among others (extract, essences, and concentrated) represents 9.2% of Brazilian exportation. Higher distances lead to physical, chemical, and microbiological changes in agricultural products. This trend could cause the deterioration of food products. Information on the sorption characteristics of roasted and grinded coffee could not be found in the literature, regardless of this culture importance. Sorption isotherms data are key information to predict optimum storage and trading conditions to ensure quality. Finally, the lack of quality may affect employees, entrepreneurs, and other professionals that works with coffee. This article presents the adsorption isotherms and thermodynamic properties of roasted and grinded coffee (Coffea arabica L.).

A B S T R A C TThe present study evaluates the influence of the level of roasting and the grind size on the moisture content and repose angle of coffee during storage. Raw coffee beans (Coffea canephora and Coffea arabica), hulled and dried, were roasted to two different levels: medium light (SCAA#65) and moderately dark (SCAA#45). The beans were then ground into three different grind sizes: fine (0.59 mm), medium (0.84 mm) and coarse (1.19 mm). An additional coffee lot was kept whole. Following grinding, samples were stored at two different temperatures (10 and 30 ºC) and analyzed after five different storage durations (0, 30, 60, 120 and 180 days). The moderately dark roast was found to have a lower moisture content. Finely ground samples had higher angles of repose. It is concluded that the grind size, level of roasting and duration of storage significantly affect the moisture content and angle of repose of coffee.Conservação de café torrado e moído durante o armazenamento. Parte 1: Teor de água e ângulo de repouso R E S U M O Objetivou-se, com este trabalho, avaliar a influência dos níveis de torrefação e moagem sobre o teor de água e ângulo de repouso de café, durante o armazenamento. Foram utilizados grãos de café cru (Coffea canephora e Coffea arabica), descascados e secos e torrados em dois níveis: média clara (SCAA#65) e moderadamente escura (SCAA#45). Os grãos foram então moídos em três granulometrias: fina (0,59 mm), média (0,84 mm) e grossa (1,19 mm) além do lote de café inteiro. Realizada a moagem as amostras foram armazenadas em duas temperaturas (10 e 30 ºC) e analisadas em cinco tempos distintos (0, 30, 60, 120 e 180 dias). A torrefação a nível moderadamente escuro proporcionou menores valores de teor de água. Obtiveram-se, com amostras mais finas, maiores valores de ângulo de repouso. Conclui-se que a granulometria, o nível de torrefação e o tempo de armazenamento afetaram significativamente o teor de água e o ângulo de repouso do café.