RESUMO O fruto de gueroba pode ser utilizado na produção de farinhas com potencial para o desenvolvimento de novos produtos oriundos da sociobiodiversidade do Cerrado. Objetivou-se estimar a cinética de secagem, bem como determinar o coeficiente de difusão efetivo e a energia de ativação para a polpa dos frutos de gueroba submetida a diferentes temperaturas de secagem. Os frutos de gueroba foram despolpados manualmente, retirando o mesocarpo com o epicarpo, sendo esse material identificado como a polpa. O material foi submetido à secagem em estufa nas temperaturas de 40, 50, 60 e 70 °C. Aos dados experimentais foram ajustados modelos de regressão não linear. O modelo mais adequado foi selecionado com base no coeficiente de determinação, erro médio relativo e estimado, teste de Qui-quadrado, AIC e BIC. Com o aumento da temperatura de secagem, menor é o tempo do processamento para se atingir o mesmo teor de água, devido ao aumento da difusividade da água no interior do produto. O modelo de Midilli apresentou o melhor ajuste aos dados experimentais obtidos. Os coeficientes de difusão efetivos da polpa dos frutos de gueroba apresentaram magnitudes entre 3,11 x 10-9 a 5,84 x 10-9 m2 s-1 para as temperaturas de 40 a 70 °C. A energia de ativação do processo foi de 18,34 kJ mol-1.

ABSTRACT The ‘Gueroba’ fruit can be used to produce flours with potential for the development of new products from the ‘Cerrado’ socio-biodiversity. The objective was to estimate the drying kinetics and determine the effective diffusion coefficient and activation energy for the pulp of ‘gueroba’ fruits subjected to different drying temperatures. ‘Gueroba’ fruits were manually pulped, removing the mesocarp with the epicarp, and this material was identified as the pulp. The material was subjected to oven drying at temperatures of 40, 50, 60 and 70 °C. Nonlinear regression models were fitted to the experimental data. The most adequate model was selected through the coefficient of determination, mean relative and estimated errors, Chi-square test, AIC and BIC. As the drying temperature increases, the processing time to achieve the same moisture content decreases, due to the increase in water diffusivity inside the product. The Midilli model showed the best fit to the experimental data obtained. The effective diffusion coefficients of the pulp of ‘gueroba’ fruits showed magnitudes between 3.11 x 10-9 to 5.84 x 10-9 m2 s-1 for temperatures from 40 to 70 °C. The activation energy of the process was 18.34 kJ mol-1.

RESUMO Objetivou-se, com este estudo, determinar as isotermas de dessorção e o calor isostérico das sementes de Annona crassiflora Mart., utilizando os critérios de informação de Akaike (AIC) e informação bayesiano de Schwarz (BIC) para auxiliar na escolha do modelo de regressão não linear. As isotermas de dessorção foram determinadas pelo método estático indireto e a atividade de água foi obtida por meio do equipamento HygroPalm; o produto foi acondicionado no equipamento em B.O.D. regulada a 10, 20, 30 e 40 °C. Os dados experimentais foram ajustados a diversos modelos de regressão não linear, pelo método Gauss-Newton. As isotermas de dessorção de sementes de Annona crassiflora Mart. podem ser representadas pelos modelos de Chung-Pfost, Copace, GAB Modificado, Henderson Modificado, Oswin Modificado, Sabbah e Sigma Copace. Contudo, o modelo Sigma Copace apresentou melhor ajuste aos dados experimentais, com memores valores de AIC e BIC, sendo escolhido para representar as isotermas de dessorção das sementes de Annona crassiflora Mart. O calor isostérico aumentou com a diminuição do teor de água, sendo necessária maior quantidade de energia para retirar a água das sementes, com valores variando de 2541,64 a 2481,56 kJ kg-1, para a faixa do teor de água de 5,69 a 14,93% base seca.

ABSTRACT The objective of this study was to determine the desorption isotherms and isosteric heat of Annona crassiflora Mart. seeds, using Akaike information criterion (AIC) and Schwarz’s Bayesian information criterion (BIC) to assist in the choice of the nonlinear regression model. The desorption isotherms were determined by indirect static method and water activity was obtained using the instrument HygroPalm; the product was put in the device in B.O.D. chamber set at 10, 20, 30 and 40 °C. Several nonlinear regression models were fitted to the experimental data by the Gauss-Newton method. The desorption isotherms of Annona crassiflora Mart. seeds can be represented by the models of Chung-Pfost, Copace, Modified GAB, Modified Henderson, Modified Oswin, Sabbah and Sigma Copace. However, the Sigma Copace model showed better fit to the experimental data, with lower AIC and BIC values, being chosen to represent the desorption isotherms of Annona crassiflora Mart seeds. Isosteric heat increased with decreasing moisture content, requiring a greater amount of energy to remove water from seeds, with values ranging from 2541.64 to 2481.56 kJ kg-1, for the moisture content range from 5.69 to 14.93% on a dry basis.

RESUMO O fruto da cajazeira (Spondias mombin L.) apresenta características relevantes para industrialização e possuem aroma agradável e sabor ácido-adocicado, possui quantidades relevantes de vitamina A e carotenoides no epicarpo do cajá. Objetivou-se, ajustar diferentes modelos matemáticos aos dados experimentais, utilizando como critérios para selecionar o melhor modelo - o Critério de Informação de Akaike (AIC) e o Critério de Informação Bayesiano de Schwarz (BIC), bem como avaliar o coeficiente de difusão efetivo e determinar a energia de ativação para o epicarpo de cajá submetido a diferentes condições de secagem. O experimento foi desenvolvido no Instituto Federal de Educação, Ciência e Tecnologia Goiano. O epicarpo dos frutos de cajá com teor de água inicial 2,89 (base seca, b.s.) foram submetidos à secagem em temperaturas de 40, 50, 60 e 70 °C até teor de água final de 0,11, 0,10, 0,09 e 0,08 (b.s.), respectivamente. O modelo de Midilli apresentou o melhor ajuste aos dados experimentais obtidos. A escolha do modelo foi confirmada pelos critérios de AIC e BIC. O aumento da temperatura de secagem promoveu aumento do coeficiente de difusão efetivo, e a energia de ativação do processo foi de 21,50 kJ mol-1.

ABSTRACT Yellow mombin (Spondias mombin L.) fruits have relevant characteristics for industrialization and exhibit a pleasant aroma and sour-sweet taste, with significant amounts of vitamin A and carotenoids in their epicarp. The objective was to fit different mathematical models to the experimental data, using as criteria to select the best model - the Akaike Information Criteria (AIC) and Schwarz’s Bayesian Information Criteria (BIC), as well as to evaluate the effective diffusion coefficient and to determine the activation energy for yellow mombin epicarp submitted to different drying conditions. The experiment was carried out at the Instituto Federal de Educação, Ciência e Tecnologia Goiano, Brazil The epicarp of yellow mombin fruits with initial moisture content of 2.89 (dry basis, d.b.) were submitted to drying at temperatures of 40, 50, 60 and 70 °C until final moisture contents of 0.11, 0.10, 0.09 and 0.08 (d.b.), respectively. The Midilli model showed the best fit to the experimental data obtained. The choice of the model was confirmed by the AIC and BIC criteria. The increase of the drying temperature promoted increase in the effective diffusion coefficient, and the activation energy of the process was 21.50 kJ mol-1.

ABSTRACT Drying is the most widely used process to ensure the quality and stability of plant products. Therefore, this study aimed to determine the effective water diffusivity and activation energy in grain sorghum during drying at different temperatures and initial moisture contents. Sorghum grains (cultivar DeKalb 640) were harvested with an initial moisture content of 0.49 kg water kg−1 dry matter. The effective diffusion coefficient was determined from different initial moisture contents of approximately 0.49, 0.40, 0.31, and 0.23 kg water kg−1 dry matter. Grains with different moisture contents were dried under four temperature conditions of 40, 60, 80, and 100 °C on perforated trays. The spherical geometry model was used for liquid diffusion. The experiment was conducted in a completely randomized design in a 4 × 4 factorial scheme (four moisture contents × four temperatures), with three replications. Data were subjected to analysis of variance and regression using the statistical software SISVAR®. Sorghum grain diffusivity increases at the same drying temperature as an increase of the initial moisture content of grains. The activation energy was higher for grains with higher initial moisture content, with values of 27.32, 26.75, 22.55, and 20.94 kJ mol−1, respectively.

ABSTRACT This study aimed to fit different mathematical models to the experimental data on drying of baru fruits (Dipteryx alata Vogel), determine and assess the effective diffusion coefficient, as well as obtain the activation energy and thermodynamic properties for the drying process under different air temperature conditions. Baru fruits with an initial moisture content of 0.429 ± 0.044 (dry basis, db) were dried in a forced air ventilation oven under four temperature conditions (40, 60, 80, and 100 °C) until reaching a moisture content of 0.065 ± 0.018 (decimal db). These data were fitted to mathematical models frequently used to represent the drying of vegetal products. The Logarithmic model presented the best fit to describe the phenomenon. The effective diffusion coefficient increased as temperature increased, being described by the Arrhenius equation, with an activation energy of 37.64 kJ mol-1. Enthalpy and entropy decreased, while Gibbs free energy increased as drying temperature increased.

Abstract The strong enhancement and localization of electromagnetic field in plasmonic systems have found applications in many areas, which include sensing and biosensing. In this paper, an overview will be provided of the use of plasmonic phenomena in sensors and biosensors with emphasis on two main topics. The first is related to possible ways to enhance the performance of sensors and biosensors based on surface plasmon resonance (SPR), where examples are given of functionalized magnetic nanoparticles, magnetoplasmonic effects and use of metamaterials for SPR sensing. The other topic is focused on surface-enhanced Raman scattering (SERS) for sensing, for which uniform, flexible, and reproducible SERS substrates have been produced. With such recent developments, there is the prospect of improving sensitivity and lowering the limit of detection in order to overcome the limitations inherent in ultrasensitive detection of chemical and biological analytes, especially at single molecule levels.

ABSTRACT: The objective of this study was to determine and evaluate the thermodynamic properties for different equilibrium moisture contents in baru fruits (Dipteryx alata Vogel), using the direct static method to obtain the experimental data. The Modified Halsey model was used to determine the thermodynamic properties of baru fruits. Results concluded that thermodynamic properties are influenced by moisture content. The water vaporization latent heat increases with the decrease in equilibrium moisture content. The baru fruit desorption process is controlled by enthalpy. Gibbs free energy is positive for the temperatures studied with the increase over desorption, which describes a non-spontaneous process.

RESUMO Com o conhecimento do equilíbrio higroscópico dos frutos de baru (Dipteryx alata Vogel), pode-se manejar adequadamente o produto visando à manutenção de seu teor de água nos níveis recomendados para o armazenamento seguro. Desta forma, objetivou-se determinar as isotermas de dessorção de água dos frutos de baru nas temperaturas de 20, 25, 30, 35 °C e atividades de água entre 0,14 e 0,80 e obter os valores do calor isostérico de dessorção em função do teor de água de equilíbrio do produto. Para obtenção do teor de água de equilíbrio foi utilizado o método estático-gravimétrico. O modelo de Halsey Modificado foi o melhor modelo recomendado para representar a higroscopicidade dos frutos de baru, cujos teores de água recomendados para o armazenamento seguro dos frutos de baru são de, no máximo, 19,9; 19,3; 18,6 e 18,0 (% b.s), para as respectivas temperaturas de 20, 25, 30 e 35 °C. O calor isostérico integral de dessorção aumenta com a redução do teor de água ocorrendo incremento da energia necessária para a remoção de água do produto.

ABSTRACT With the knowledge on the hygroscopic equilibrium of the baru (Dipteryx alata Vogel) fruit, the product can be adequately handled to maintain the moisture content at the levels recommended for safe storage. Thus, this paper aimed to determine the water desorption isotherms of baru fruits at temperatures of 20, 25, 30 and 35 °C, and water activity between 0.14 and 0.80, and obtain the values of isosteric heat of desorption as a function of the equilibrium moisture content of the product. The equilibrium moisture content was obtained using the static-gravimetric method. Modified Halsey was the best model recommended to represent the hygroscopicity of baru fruits. The recommended moisture contents for safe storage of baru fruits are not more than 19.9, 19.3, 18.6 and 18.0 (%, d.b.) for the respective temperatures of 20, 25, 30 and 35 °C. The integral isosteric heat of desorption increases as the water content decreases, leading to an increment in the energy required to remove water from the product.

In this work we take advantage of the polyelectrolyte character of some Brazilian native gums to fabricate electrically conductive, nanostructured films. The gums Sterculia urens, (caraia), Sterculia striata (chicha) or Anadenanthera macrocarpa Benth were assembled in conjunction with poly(o-methoxyaniline) (POMA) in the form of layered nanostructured films using the layer-by-layer (LbL) technique. All the LbL films displayed a well-defined electroactivity, as confirmed via cyclic voltammetry. In comparison to POMA LbL films fabricated with conventional polyelectrolytes (viz. poly(vinyl sulfonic acid)-PVS), the presence of the gums in the LbL films increased remarkably the electrochemical stability of the films.