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.

ResumoA escoabilidade é uma importante característica do manuseio para a eficiência e a confiabilidade das operações pós-colheita, sendo regida pelas propriedades físicas do produto. A determinação das propriedades físicas é um importante fator na formulação de projetos de maquinários e dimensionamento de operações pós-colheita, podendo impactar consideravelmente na qualidade do produto, influenciando diretamente o custo da operação e o lucro da empresa. Assim, objetivou-se avaliar e determinar as propriedades físicas: ângulo de repouso, massa específica unitária e aparente, porosidade e as coordenadas de cor, análise da granulometria, teor de água, atividade de água, ângulo de atrito interno e efetivo ângulo de atrito interno do café, bem como avaliar a influência de diferentes níveis de torra e granulometria sobre essas propriedades. 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). Após a torrefação, os grãos foram moídos em três granulometrias: fina (0,59 mm), média (0,84 mm) e grossa (1,19 mm), segundo normas de classificação da ABIC, além de mantido o lote de café inteiro. A granulometria e o nível de torrefação afetaram significativamente as propriedades físicas do café. As amostras de café torradas ao nível moderadamente escuro obtiveram menores valores de teor de água, atividade de água, ângulo de repouso, massa específica unitária e aparente. Já os cafés de granulometria mais fina apresentaram aumento de ângulo de atrito interno e efetivo ângulo de atrito interno, ângulo de repouso, massa específica unitária e aparente, porosidade e decréscimo de atividade de água. Palavras-chave: Propriedades físicas, pós-colheita, escoabilidade AbstractFlowability is an important characteristic of handling process for efficiency and reliability purpose of post-harvest operations, which are governed by the physical properties of the product. Physical properties determination is an important factor for formulation of machinery projects and sizing of post-harvest operations, which may impact considerably on the products quality, influencing directly the operation cost and company profit. Thus, the objective of this work was to evaluate and determinate some physical properties (repose angle, unit and bulk density, porosity and color coordinates, particle size, moisture content, water activity, angle of internal friction and effective angle of internal friction)

RESUMOThe aim of the present study is to model the dehydration process of pineapple slices through infrared drying, as well as to determine the critical moisture content and the critical time to the dehydration process. Pineapple slices were cut 5.0 mm thick and 2.0 cm diameter, and dried by an infrared heating source equipped with a built-in scale at accuracy of 0.001 g, under the temperatures of 50, 60, 70, 80, 90 and 100 °C, until constant weight was reached. Mass variation readings were taken at 1.0 min intervals. The mathematical models met the experimental data. The modified model by Henderson and Pabis best represented the data about the drying process. The higher drying temperature led to higher critical moisture content (from 2.205 to 2.450 kgw kg dm

ABSTRACT:Roasting is one of the most complex coffee processing steps due to simultaneous transfers of heat and mass. During this process, beans lose mass because of fast physical and chemical changes that will set color and flavor of the commercial coffee beverage. Therefore, we aimed at assessing the kinetics of mass loss in commercially roasted coffee beans according to heating throughout the processing. For that, we used samples of 350-g Arabica coffee processed grains with water content of 0.1217 kg a kg -1 , in addition to a continuous roaster with firing gas. The roaster had initial temperatures of 285, 325, 345 and 380 °C, decreasing during the process up to 255, 285, 305 and 335 °C respectively. Mass loss was calculated by the difference between grain weight before and after roasting. We observed a linear variation directly dependent on roaster temperature. For each temperature during the process was obtained a constant mass loss rate, which was reported by the Arrhenius model with r 2 above 0.98. In a roaster in non-isothermal conditions, the required activation energy to start the mass loss in a commercial coffee roasting index was 52.27 kJ mol -1 . KEYWORDS:Coffea arabica, mass decrease, roasting degree, roasting temperature, nonisothermal roasting CINÉTICA DA PERDA DE MASSA DO CAFÉ ARÁBICA DURANTE A TORRAÇÃO RESUMO:A torrefação é uma das etapas mais complexa do processamento do café devido à transferência simultânea de calor e massa, em que os grãos perdem massa devido à rapidez das mudanças físicas e químicas, necessárias para produzir a cor e o aroma do café comercial. Assim, objetivou-se com este trabalho determinar a cinética da perda de massa dos grãos de café torrados comercialmente em função da temperatura do processo. Foram usadas amostras de 350 g de grãos beneficiados de café arábica com teor de água de 0,1217 kg a kg -1 . Usou-se um torrador com queima de gás constante e temperaturas iniciais de 285; 325; 345 e 380 °C, que diminuíram durante a operação até equilibrar-se em 255; 285; 305 e 335 °C, respectivamente. A perda de massa foi calculada a partir do peso dos grãos antes e depois da torração, sendo observada uma variação linear dependente diretamente da temperatura do torrador. Para cada temperatura do processo, foi obtida uma taxa constante de perda de massa, que foi relacionada pelo modelo de Arrhenius com r 2 acima de 0,98. Em condições não isotérmicas do torrador, a energia de ativação necessária para iniciar a perda de massa, em índices de torração comercial do café, foi 52,27 kJ mol -1 .