Abstract Thus, the objective of this work was to evaluate the performance of industrial drying and the quality of soybean grains using a direct-fire furnace automatically fed by wood chips. To represent the grains before drying, four samples were collected together with the sampling of the loads in the trucks carried out to classify the product in the storage unit. At drying, performance evaluations and specific energy consumption were carried out. The grains were evaluated for moisture content, germination, electrical conductivity, apparent specific mass, color, acidity index, and PAHs. Drying showed an average efficiency of 75.50%. The average chip consumption was 0.4403 kg of chip/kg of evaporated water. The specific energy consumption was 8,099.50 kJ/kg of evaporated water. The grains showed differences after drying in the characteristics of germination, electrical conductivity, and chroma. Six PAHs were detected in the samples before drying: (B(a)A, Chr, 5 MC, B(j)F, Dib(ai)P, and IcdP). After drying, in addition to the PAHs obtained before drying, five more were detected (B(b)F, B(k)F, B(a)P, Dib(al)P, and Dib(ah)A). Mean PAH concentrations were higher than the maximum values allowed by European Union legislation.

Abstract The objective of this work was to evaluate the drying performance, the quality of the corn grain and the contamination by polycyclic aromatic hydrocarbons (PAHs) using a direct-fired furnace fed automatically by wood chips. Samples were collected at five-minute intervals, 12 samples before drying and 12 samples after drying. The following experimental evaluations were carried out: dryer – performance and fuel consumption; grains – moisture content, germination, electrical conductivity, apparent specific mass, mass of a thousand grains, color and PAHs. The dryer showed an average efficiency of 83.61%. The average consumption of wood chips was 0.3932 kg of chips per kilogram of evaporated water. Differences were observed in the grains after drying for the characteristics of mass of a thousand grains, apparent specific mass, germination and electrical conductivity. The average concentrations of PAHs in corn grains were higher than the maximum values allowed by the European Union legislation.

Abstract The objective of this study was to evaluate the drying system using a dryer with furnace automatically fed with eucalyptus chips and another dryer manually fed with eucalyptus firewood, as well as assessing the quality of corn grains. Harvest was mechanically performed and the grains were transported by trucks to the storage unit for drying. Corn grain drying was conducted in mixed-flow dryers with a nominal capacity of 100 tons per hour. For air heating, two direct-fired furnaces were used, one automatically fed with eucalyptus chips and the other manually fed with firewood. Corn grains were evaluated for moisture content, apparent specific mass, thousand-grain weight, polycyclic aromatic hydrocarbons (PAHs), electrical conductivity and color. Drying corn grains with direct fire using firewood or chips as fuel causes contamination by PAHs. In general, the use of firewood or chips did not influence the quality of thousand-grain weight, apparent specific mass and color, while the use of chips increased electrical conductivity. It is essential that research advances in this subject, prioritizing the contamination of food, with proven carcinogenic activity, which should be treated as a high risk to public health.

Abstract The Croton urucurana Baill species is known in Brazil as “sangra d’água” and is popular due to its medicinal properties. For better processing of herbal medicines, it is essential that efficient drying and storage techniques are developed and that compounds are preserved. Therefore, this study aimed to select models through multivariate cluster analysis applying Akaike (AIC) and Bayesian information criteria (BIC) to describe Croton urucurana leaves drying kinetics at different temperatures (40-70 °C). The initial moisture content in Croton urucurana leaves was 1.791, 1.841, 2.196 and 2.144 kg water kg dry matter-1, and 8.25, 7.75, 4.25 and 2 hours were required to reach hygroscopic equilibrium, with a final moisture content of 0.134, 0.105, 0.065 and 0.0601 kg water kg dry matter-1, at 40, 50, 60 and 70 °C, respectively. The models with the greatest similarity to the experimental data were Diffusion Approximation; Cavalcanti Mata; Two-term; Two-term Exponential; Modified Henderson & Pabis; Logarithmic; Midilli; Page and Verma. The multivariate cluster technique associated with AIC and BIC criteria during model selection is a great applicability tool to help decision-making when evaluating the drying plant leaves. The Cavalcanti Mata mathematical model was selected to represent the drying kinetics.

Abstract Araticum (Annona crassiflora) fruits have relevant characteristics for industrialization, a characteristic aroma and a slightly acidic flavor, with relevant amounts of vitamins A, C, B1 and B2. The objective of this study was to fit different mathematical models to the experimental data, evaluate the effective diffusion coefficient and determine the activation energy for the araticum epicarp subjected to different drying conditions. The epicarps of araticum fruits were dried at temperatures of 40, 50, 60 and 70 °C. Midilli, Logarithmic and Two Terms models can be used to represent the drying of araticum epicarp, and the Two Terms model was selected according to the Akaike Information Criterion (AIC) and Schwarz’s Bayesian Information Criterion (BIC). The linear model satisfactorily represented the effective diffusion coefficient as a function of drying temperature. In the evaluation of enthalpy, entropy and Gibbs free energy, both enthalpy and entropy tend to decrease when temperature increases. The higher the temperature used for drying of araticum epicarp, the lower the value of diffusivity, i.e., the lower the resistance to water removal.

Abstract The drying is one of the stages of processing Brazil nuts, being an important stage due to the high moisture content and water activity of the product. This study aimed to adjust mathematical models to the drying kinetics data of Brazil nuts, calculating the effective diffusion coefficient and obtaining activation energy for the drying process. Brazil nuts were collected in amazon region, and then the product was homogenized for processing. The nuts were subjected to drying in a forced ventilation oven at temperatures of 40, 50, 60, 70 and 80 °C in 4 replicates, each one consisting of approximately 200 g of samples in aluminum containers. Mathematical models were adjusted to the experimental data of the moisture content ratio. Thompson, Midilli, Logarithmic and Two Terms models are suitable for estimating the drying of Brazil nuts. The Two Terms model was selected to represent the drying phenomenon for presenting better results in the analyzed parameters. The effective diffusion coefficient increased with increasing temperature and the activation energy for the liquid diffusion in the drying was 35.69 kJ mol-1.

ABSTRACT. Drying is an important step in the post-harvest processes as a way of product conservation and quality preservation. In this context, this study aimed to evaluate the effect of continuous and intermittent drying of maize grains with different rest periods on the integrity of their micro- and macroscopic structures. Maize grains were harvested with a moisture content of 0.3399 ± 0.001 dry basis (db) and subjected to continuous and intermittent drying with 4, 8, 12, and 16 hours of rest period. An experimental fixed-bed dryer, with controlled drying air conditions at a temperature of 100 °C and air flow of 1.5 m3 min.−1 m−2 (12 m3 min.−1 m−3), was used. Continuous drying was completed with a moisture content of 0.1628 ± 0.0003 db, whereas intermittent drying was interrupted with 0.2195 ± 0.0002 db and resumed after rest. The drying rate, integrity through grain images, the conformation of particles through scanning electron microscopy, and cell membrane integrity were evaluated. The drying rate increased with an increase in the rest period, the increase in rest period reduced the intensity of cracks, and the reduction in rest period led to higher dispersion and reduction in the size of starch granules and lower integrity of cell membranes.

RESUMO O trigo mourisco tem se destacado na cadeia alimentícia por não possuir glúten em sua farinha. Por ser uma cultura relativamente nova no meio agrícola, faltam informações referentes ao seu processamento, dentre as etapas pós-colheita a secagem é uma das mais importantes. O objetivo do presente trabalho foi descrever o processo de secagem de grãos de trigo mourisco. Os grãos foram colhidos com teor de água de 0.41 ± 0.01 (b.s.) e submetidos a secagem em secador experimental nas temperaturas de 40, 50, 60, 70 e 80 °C, e velocidade do ar de 0.8 m s-1. Determinou-se a taxa de secagem e ajustou-se aos dados experimentais modelos matemáticos frequentemente utilizados para a descrição da secagem de diversos produtos agrícolas. A seleção dos modelos foi baseada no método de regressão não linear de Gauss-Newton e complementada pelo Critério de Informação de Akaike e Critério de Informação Bayesiano de Schwarz’s. Conclui-se que, a taxa de redução da água foi maior para maiores temperaturas e diminuiu com o aumento do tempo de secagem; o modelo de Midilli é recomendado para representar a cinética de secagem dos grãos nas temperaturas de 40, 60 e 70 ºC; para a temperaturas de 50 e 80 ºC recomenda-se o modelo de aproximação da difusão; os coeficientes de difusão efetivo apresentaram magnitude de 1.8990 a 17. 8831 × 10-11 m2 s-1 e; a energia de ativação requerida para iniciar o processo de secagem foi de 49.75 kJ mol-1.

ABSTRACT Buckwheat has become important in the food sector as its flour does not contain gluten. Since buckwheat is a relatively new crop in the agricultural environment, there is little information available regarding its processing. Drying is one of the most important post-harvest stages of buckwheat. The aim of the present study was to describe the drying process of buckwheat grains. Buckwheat grains with a moisture content of 0.41 ± 0.01 (dry basis, d.b.) were harvested, followed by drying in an experimental dryer at the temperatures of 40, 50, 60, 70, and 80 °C, at an air speed of 0.8 m s-1. The drying rate was determined, and the mathematical models generally employed to describe the drying process of several agricultural products were fitted to the experimentally obtained data. Model selection was based on the Gauss-Newton non-linear regression method and was complemented by Akaike Information Criterion and Schwarz’s Bayesian Information Criterion. It was concluded that the drying rate increased with an increase in temperature and decreased with an increase in drying time. It is recommended to use the Midilli model to represent the drying kinetics of buckwheat grains at the temperatures of 40, 60, and 70 °C, while the Approximation of diffusion model is recommended for the temperatures of 50 and 80 °C. The magnitudes of effective diffusion coefficients ranged from 1.8990 × 10-11 m2 s-1 to 17.8831 × 10-11 m2 s-1. The activation energy required to initiate the drying process was determined to be 49.75 kJ mol-1.

RESUMO As propriedades mecânicas de produtos agrícolas são fundamentais para o correto desenho de projetos ou dimensionamento de equipamentos de processamento e estabelecimento de parâmetros sobre a carga suportada. Para avaliar o efeito da secagem com intermitência, foi montado um experimento em delineamento inteiramente casualizado, com cinco tratamentos (secagem contínua e intermitente com 4; 8; 12 e 16 h de repouso) e quatro repetições. Os grãos de milho, cultivar Cargo TL, foram colhidos com teor de água de 25.37% b.u., submetidos a secagem em um secador experimental de camada fixa, ajustado à temperatura de 100 ºC e fluxo de ar de 1.5 m3 min-1 m-2. A secagem decorreu até que os grãos atingissem o teor de água de 14±0.3% b.u. Para a secagem intermitente o processo foi interrompido com 18±0.2% de teor de água b.u. e prosseguiu após o repouso, até atingir o teor de água final. Para a análise foram selecionados aleatoriamente 10 grãos por repetição e submetidos ao teste de compressão uniaxial depois de determinar as suas dimensões. Avaliou-se a força de ruptura, deformação máxima, energia consumida até o ponto de ruptura, módulo de tenacidade, dureza e taxa de redução da água durante a secagem. Concluiu-se que, o aumentou do tempo de repouso promoveu um aumento linear nos valores da força de ruptura e dureza; o módulo de tenacidade, energia e deformação não foram afetados pelo tempo de repouso; o aumento do tempo de repouso contribuiu para o aumento da taxa de redução da água.

ABSTRACT Mechanical properties of agricultural products are essential for a proper project design or processing equipment dimensioning, as well as for establishment of parameters on the supported load. An experiment was set up in a completely randomized design, with five treatments (continuous and intermittent drying under 4, 8, 12, and 16 h of rest period) and four replications, to evaluate the effect of intermittent drying. Corn kernels of the cultivar Cargo TL were harvested with a moisture content of 25.37% wb and submitted to drying in an experimental fixed bed dryer set to a temperature of 100 °C and an airflow of 1.5 m3 min-1 m-2. Drying was performed until the kernels reached a moisture content of 14±0.3% wb. The process was interrupted in the intermittent drying with a moisture content of 18±0.2% wb and continued after rest period until the final moisture content was reached. The analysis consisted of 10 kernels randomly selected per replication and submitted to the uniaxial compression test after determining their dimensions. Rupture force, maximum deformation, energy to rupture point, modulus of toughness, hardness, and drying rate during drying were evaluated. The increase in rest period promoted a linear increase in the rupture force and hardness. Modulus of toughness, energy to rupture point, and maximum deformation were not affected by the rest period. The increase in rest period contributed to increasing the drying rate.

ABSTRACT. With the depletion of fossil fuel resources accelerating the search for renewable energy sources, studies on agricultural products containing a significant amount of oil in their compositions have intensified. The objective of this work was to investigate the fatty acid profile and the physiological quality of the oil extracted from niger seeds dried at different temperatures. The seeds were dried at 40, 50, 60, and 70°C, until their moisture content reached 8.5 ± 1% (wet basis). The physiological properties of niger seeds were determined by assessing their germination, germination speed index, mean germination time, cold test, accelerated aging with a saturated solution, emergence percentage, and emergence speed index. The quality of the oil was evaluated using gas chromatography, based on the fatty acid profile. We concluded that drying air temperatures of 40 and 50°C did not compromise the physiological quality of niger seeds. However, the 70°C drying temperature seriously impaired seed quality. The drying temperatures that were used in this study did not substantially alter the fatty acid profile of niger oil.