Daniel Emanuel Cabral de Oliveira

Qualidade fisiológica das sementes de soja armazenadas em diferentes condições

Propos-se, neste trabalho, avaliar a qualidade fisiologica das sementes de soja ao longo do armazenamento durante 180 dias em diferentes teores de agua e em duas condicoes de temperatura. Foram utilizadas sementes de soja, cultivar CD 242 RR com teores de agua iniciais de 12, 13 e 14% (b.u.). As sementes foram adquiridas com o teor de agua de 11,0% (b.u.); em seguida, foram umedecidas em câmara BOD a 20 oC e 85% de umidade relativa, homogeneizadas e acondicionadas em sacos plasticos de polipropileno; as embalagens foram mantidas em dois ambientes distintos. Com vista a avaliacao das sementes ao longo do armazenamento foram realizadas as analises de teor de agua, germinacao, primeira contagem da germinacao, indice de velocidade de germinacao e condutividade eletrica. O experimento foi conduzido no delineamento inteiramente casualizado, segundo o esquema fatorial triplo 2 x 4 x 3 (duas condicoes de armazenamento, quatro tempos de armazenamento e tres teores de agua), com tres repeticoes. O teor de agua inicial influencia na qualidade das sementes de soja durante o armazenamento. O ambiente climatizado (20 oC) proporciona melhores resultados em todas as caracteristicas estudadas.

Isotermas de dessorção e calor isostérico dos frutos de crambe

This study aimed to adjust different mathematical models to experimental data of hygroscopicity of crambe fruits, selecting one that best represented the phenomenon, and obtain the values of the isosteric heat of desorption as a function of equilibrium moisture content. To obtain an equilibrium moisture content, crambe fruit was used with an initial moisture content of 26.0% (dry basis) and static gravimetric method. For each replicate 10 g of fruit were placed surrounded by a permeable fabric to permit air contact with the product and placed within the desiccators. To control the relative humidity inside the desiccators, saturated solutions were used. The desiccators were placed in incubator B.O.D., adjusted to temperatures of 25, 30, 35 and 40 °C. The equilibrium moisture content of crambe fruits is directly proportional to water activity and decreases with increasing temperature for the same value of equilibrium relative humidity. Based on statistical parameters, the models of Copace and Modified Oswin are those that best represent the hygroscopicity of crambe fruits compared to other tested models. The isosteric heat increases with decrease in equilibrium moisture content and requires a larger amount of energy to remove water from the crambe fruit.

Propriedades termodinâmicas de grãos de milho para diferentes teores de água de equilíbrio

The study of thermodynamic properties provides knowledge on the sorbent affinity for water and spontaneity of the sorption process, being important to design drying equipments. This study aimed at determining and evaluating the thermodynamic properties of different equilibrium moisture contents in maize grains, by using the indirect static method. The experiment was conducted in Rio Verde, Goias State, Brazil, with maize grains (AG 7088 cultivar) presenting an initial moisture content of 23.3% ( dry basis - d.b.), which were dried (40oC) to achieve the moisture content of 14.4% ( d.b.). It was observed that the thermodynamic properties were influenced by moisture content, the integral isosteric heat of desorption increased with the decrease in the equilibrium moisture content, the desorption process of the AG 7088 maize cultivar was controlled by enthalpy and t he Gibbs free energy was positive for the temperatures evaluated, increasing along the desorption process, showing to be a non-spontaneous process.

Modelagem da contração volumétrica do feijão-adzuki durante a secagem

Beans are a protein rich food of enormous importance in human nutrition and are the most important source of proteins for low income populations. Adzuki bean (Vigna ungulate) is originated from China and is increasingly important in Brazil where is cultivated mainly by the Japanese colony. The objective of this study was to adjust different mathematical models to experimental values of the unitary volumetric contraction of the adzuki grain submitted to drying under three different air conditions. The grains at an initial moisture content of 92.08% ( dry basis %) were exposed to drying in an forced ventilation oven at temperatures of 40, 60, and 80 °C until they reached a moisture content of 14.8%, dry basis. To the experimental data mathematical models were adjusted in order to have the representation of the volumetric shrinkage of the agricultural products. The models were evaluated by means of the determination coefficient, of the mean relative and estimated errors of the chi-square test. The results showed that the grain moisture content and the drying temperature had a significant influence on the unitary volumetric shrinkage of the grain and that this phenomenon is satisfactorily described by the modified Bala & Woods model. The unitary volumetric shrinkage of the grains may be represented by a sole model for drying temperatures between 60 and 80 °C. Additional keywords: Bala & Woods modified model; grain moisture content; models identity; mathematical models. Cientifica, Jaboticabal, v.42, n.1, p.23–31, 2014 ISSN: 1984-5529

Crambe fruit drying with natural air in stationary dryers

The aim of this study was to assess the drying behavior and quality of crambe fruit seeds dried with natural air and submitted to different airflows in stationary dryers. Dryings were carried out in July and September 2014. The experiment consisted of three treatments of drying the crambe fruits with natural air in stationary dryers with airflows of 10.08, 15.05, and 25.03 m3 min−1 t−1 and a control treatment composed of crambe fruits with an initial moisture content without going through the drying process. After drying, tests of moisture content, germination, germination rate index, and electrical conductivity were performed in order to compare the treatments. The data were submitted to analysis of variance and mean comparison by the Tukey’s test at 5% significance. Among the airflows used in the experiment in both natural air dryings in July and September, no interference was observed for crambe fruit quality. Drying carried out in September was faster and showed a lower expenditure and cost of electricity when compared to that performed in July, which is due to better climatic conditions. No difference was observed in the drying times between airflows, but the drying with natural air using an airflow of 15.05 m3 min−1 t−1 was more profitable.