The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol^-1.

A higroscopicidade de sementes fornece informações essenciais para otimização de processos de secagem, armazenamento e desenvolvimento de embalagens. O objetivo neste trabalho foi determinar as isotermas de dessorção das sementes de pimenta (Capsicum chinense L.), variedade Cabacinha, para diferentes condições de temperatura e atividade de água utilizando-se o método estático indireto, sendo a atividade de água (aw) determinada por meio do equipamento Hygropalm Model Aw1. Aos dados experimentais foram ajustados modelos matemáticos frequentemente utilizados para representação da higroscopicidade de produtos agrícolas. Para uma atividade de água constante o aumento da temperatura reduz o teor de água de equilíbrio higroscópico das sementes de pimenta. As isotermas de dessorção apresentam formato sigmoidal do tipo II. Os modelos de Cavalcanti Mata, Chen Clayton, Chung Pfost, Chung Pfost Modificado, Henderson e Henderson Modificado são adequados para representar a higroscopicidade das sementes de pimenta Cabacinha para a faixa de temperatura de 10 a 40 °C e atividade de água de 0,213 a 0,975.

Drying air temperature has direct influence on seed quality, especially for vegetable species harvested with high moisture content. This study aimed to determine and model the drying curves of ‘Cabacinha’ pepper seeds (Capsicum chinense L.) at different temperatures, and to evaluate their physiological quality after drying and during storage. The experimental design was completely randomized in a 3 x 3 factorial scheme, with three drying temperatures (35, 38 and 42 °C) and three storage periods (0, 4 and 8 months), with four replicates. Seed quality was evaluated by germination test, first germination count, accelerated aging, electrical conductivity, seedling emergence, and speed of emergence. The Two Terms is the model that best represents the drying curves of ‘Cabacinha’ pepper seeds at temperatures of 35, 38 and 42 °C. Higher germination and vigor values are obtained in seeds dried at 35 and 38 °C. Drying at 42 °C and storage reduce the physiological quality of the seeds.

Drying is one of the most important steps of the post-harvest of pepper seeds and must be performed carefully so as not to impair the quality of seeds. The study of thermodynamic properties provides information about the behavior of water in agriculture products and the energy requirement for removal thereof during the drying pro­cess. Based on the above, this study aimed to determine and evaluate the thermodynamic properties for different equilibrium moisture contents in pepper seeds of the variety ‘Cabacinha’. Seeds with an initial moisture content of 22.7% on dry basis (d.b.) were subjected to drying at 40 °C, until reaching moisture content of 3.9% (d.b.). Based on the obtained results, it is concluded that the integral isosteric heat of desorption, the Gibbs free energy, the differential enthalpy and entropy increase with the reduction of the moisture content of pepper seeds. The Gibbs free energy showed positive values, indicating that the process of desorption is not spontaneous. The theory of the enthalpy-entropy compensation can be applied to the desorption process, since this is controlled by enthalpy.

Bitter melon (Momordica charantia L.) is a versatile plant that can be consumed as a food and has therapeutic applications. Studying its drying process is important to maintain their leaf quality during storage. The objective of this study was to evaluate the drying kinetics of bitter melon leaves and determine their thermodynamic properties. The leaves were placed in polyethylene trays and subjected to drying in an oven at temperatures of 20, 30, 40, and 50 °C until reaching hygroscopic equilibrium. The experimental data were fitted to several non-linear regression models to characterize the drying process. The Arrhenius model was used to obtain the coefficients of diffusion and the activation energy, which were used to calculate the enthalpy, entropy, and the Gibbs free energy. Midilli and Page were the best models to represent the drying kinetics of bitter melon leaves at temperatures of 20, 30, 40, and 50 °C. Increases in the drying air temperature increased the Gibbs free energy and water diffusivity in the interior of the leaves. Enthalpy and entropy decreased as the temperature was increased.

Germination does not guarantee plant establishment if there is no efficient and enough reserve mobilization from seeds to the initial seedling growth, mainly in adverse situations. Therefore, this study aimed to evaluate the mobilization of reserves in soybean seeds under water restriction. Four soybean seed lots previously stored for one year were used in the study. To simulate water stress, we used polyethylene glycol (PEG) solutions at concentrations of 0.0, -0.1, and -0.2 MPa. The number of normal, infected and abnormal seedlings were evaluated, along with the number of dead and hard seeds. The radicle, hypocotyl, and cotyledons were separated to determine the dry weight based on the total seed reserve available for mobilization. From this value, the seed reserve reduction, relative dry matter yield, seed reserve reduction rate, and reserve conversion efficiency into dry seedling weight were determined. The increase in water restriction elevates the reserve consumption during the germination process. Vigorous seeds are more efficient in mobilizing and converting grains reserve in dry seedling mass. In less vigorous seeds, mainly those on water restriction, the increase in reserve consumption does not result in conversion into dry seedling mass.