ABSTRACT This study aimed to assess the drying kinetics of red and yellow chili peppers, “dedo-de-moça” variety, at different temperatures (35, 45, 55, and 70 °C) and model this phenomenon mathematically. We also evaluated the effect of these drying air temperatures on pepper fruit color. Pepper fruits were dried in a forced-air circulation dryer. Ten mathematical models were fitted to the experimental data by nonlinear regression analysis. After drying, pepper samples were analyzed for the following colorimetric parameters: lightness (L*), chroma or saturation (c), and hue angle (h), in order to determine the influence of drying air temperature on fruit coloration. Our findings showed that the higher the air temperature, the faster the drying process. Midilli model fitted well to all temperature data and best represented the drying kinetics of “dedo-de-moça” chili peppers. Moreover, fruit color was affected by the drying air temperatures, in which the higher the drying air temperature, the greater the color variation.

RESUMO Esta pesquisa focou na determinação do equilíbrio higroscópico e do calor isostérico da pimenta Dedo-de-Moça (Capsicum baccatum) sob diferentes condições controladas de temperatura e umidade relativa do ar. Foi ajustado o modelo que melhor representa o comportamento isotérmico de sorção entre os modelos descritos na literatura, bem como a proposta de um novo modelo e parâmetros que satisfazem com representatividade o fenômeno de higroscopicidade e calor isostérico. As temperaturas utilizadas foram 30, 50 e 70 ºC, com níveis de atividade de água variando de 0.11 a 0.84. O calor isostérico integral de sorção da pimenta Dedo-de-Moça, para o teor de água entre 0.07 a 0.54 (b. s.), variou de 3641.66 a 2614.38 kJ kg-1. O modelo que melhor se representa o comportamento do equilíbrio higroscópico e calor isostérico é o novo modelo proposto no presente estudo, com R2 igual a 0.97.

ABSTRACT This study focuses on the determination of the hygroscopic equilibrium and isosteric heat of the aji chili pepper (Capsicum baccatum) under different controlled temperature and relative air humidity conditions. In addition, the objective was to adjust the model among the existing literature models that best represent the isothermal sorption behavior, as well as propose a new model to represent this phenomenon. Having obtained the mathematical models and experimental data, the best model and parameters that represent the hygroscopicity and the isosteric heat satisfactorily was determined. The temperatures used were 30, 55, and 70 °C, with water activity levels from 0.11 to 0.84. The model that best fit the data had a R2 value of 0.97. The integral isosteric heat of sorption for ‘Dedo-de-Moça’ chili pepper within a moisture content from 0.07 to 0.55 (dry basis) ranged from 3641.66 to 2614.38 kJ kg-1.

<title>RESUMO</title><p>A secagem é um processo utilizado para retirar certa quantidade de água do produto com a finalidade de aumentar a vida de prateleira, minimizar as perdas na pós-colheita, do excesso da produção e devido a contração volumétrica reduzir os custos de embalagem, transportes e armazenamento. Diante do exposto objetivou-se no trabalho fazer o estudo da cinética de secagem, análise da contração volumétrica e obter os valores de difusão líquida durante o processo de secagem de figo. Foram utilizados figos do comércio da cidade de Niterói, RJ, e submetidos à secagem em condições controladas de temperaturas do ar (40, 55 e 70 °C). Aos dados experimentais foram ajustados modelos matemáticos para a representação do processo de contração volumétrica e de secagem de produtos agrícolas. O modelo polinomial teve o melhor ajuste aos dados observados para a faixa de temperatura estudada representando melhor a contração volumétrica do figo e para secagem o modelo de Midilli obteve o melhor ajuste. A difusão líquida aumenta com a elevação da temperatura apresentando valores entre 1,76 x 10^-11 e 8,78 x 10^-11 m²s^-1.</p>

<title>ABSTRACT</title><p>The drying process is used to remove some water from the product, in order to increase the shelf life, to minimize post-harvest losses in excess of production and owing to the shrinkage, reducing the cost of packaging, transport and storage. Thus, the objective of this work was to study the drying of fig, analysis of shrinkage, as well as obtaining the values of liquid diffusion during the fig drying process. Figs were used from some Niterói Markets and subjected to drying under controlled air temperatures (40, 55 and 70 °C). Mathematical models were adjusted to experimental data to represent the processes of shrinkage and drying of agricultural products. The polynomial model and Midilli had the best fit for the observed data for the temperature range studied, representing the best shrinkage and drying fig, respectively. The liquid diffusion increases with increasing temperature with values between 1.76 x 10^-11 and 8.78 x 10-11 m² s^-1.</p>