Abstract The banana is one of the most consumed fruits in the world, but it has little shelf life due to its high water activity. Drying is able to increase shelf life and pre-treatments can optimize the process. The objective was to study the solar drying kinetics and evaluate the effect of pre-treatments on the drying kinetics and physico-chemical quality of 'Prata' bananas. The drying was carried out in a solar dryer and the pre-treatments consisted of immersing the samples in solutions of water, citric acid (1%) and lemon juice (10%). Water loss, drying kinetics, mathematical models and physical-chemical and colorimetric characteristics of fresh and dried bananas were evaluated. The drying rate was higher at the beginning and stabilized after 20 hours. The mathematical model of Midilli and Kucuk was the one that best fit the experimental data. The water content, ascorbic acid and the parameters L *, b *, C * and h ° reduced after drying. Reducing sugars and a * coordinate increased and the acidity was not changed with drying. The solar drying of 'Prata' bananas is a sustainable and economical way to make a product available with a longer shelf life.

RESUMO As nanoferritas mistas de Ni0,5Zn0,5Fe2O4 e Ni0,2Cu0,3Zn0,5Fe2O4 foram sintetizadas por reação de combustão usando ureia como combustível e um reator cônico como fonte de aquecimento para produção em bateladas de 10 g, e então, testadas como nanocatalisadores heterogêneos nas reações de transesterificação e esterificação metílica e etílica do óleo de soja para produção de biodiesel. Durante as sínteses foram registrados o tempo e a temperatura das reações, bem como observadas a liberação de gases e a cor das chamas emitidas. As amostras foram caracterizadas por DRX, EDX, FTIR, MEV/EDS, BET e cromatografia gasosa. Os testes reacionais foram executados para 10 g do óleo em duração de 1 h, razão molar 1:12 óleo:álcool, 2 % (m/m) de catalisador e conduzidas a 180 ºC. Os difratogramas de DRX e os espectros de FTIR revelaram presença da fase espinélio inverso tipo B(AB)2O4. A morfologia apresentou a formação de aglomerados de aspecto frágil e elevada área de superfície. As análises cromatográficas produziram excelentes resultados nas reações de esterificação para ambas amostras nas condições testadas, com destaque especial para Ni0,5Zn0,5Fe2O4, cujas conversões foram de 91,4 % em ésteres metílicos e de 77,8 % em ésteres etílicos, enquanto que a amostra Ni0,2Cu0,3Zn0,5Fe2O4 apresentou conversões de 75,1 e 65,1 %, respectivamente. As conversões na transesterificação metílica e etílica foram de 14 e 2 % para Ni0,5Zn0,5Fe2O4 e de 11 e 3 % para Ni0,2Cu0,3Zn0,5Fe2O4.

ABSTRACT The mixed nanoferrites of Ni0.5Zn0.5Fe2O4 and Ni0.2Cu0.3Zn0.5Fe2O4 were synthesized by combustion reaction using urea as fuel and a conical reactor as heating source in batches of 10 g, and then tested as heterogeneous nanocatalysts in the transesterification and esterification reaction of soya bean oil using the methyl and ethyl routes to biodiesel production. During the synthesis the time and temperature of the reactions were measured, and the evolved gases and the color of the emitted flames were observed. The samples were characterized by XRD, EDX, FTIR, SEM/EDS, BET and gas chromatography. The reaction tests were carried out with 10 g of oil for 1 h, oil:alcohol molar ratio of 1:12, 2 % (w/w) of catalyst, and conducted at 180 °C. The XRD patterns and the FTIR spectra revealed the presence of the inverse spinel phase type B(AB)2O4. The morphology showed the formation of agglomerates with fragile morphology and high surface area. The chromatographic analysis produced excellent results in the esterification reactions for both samples in the tested conditions, with special emphasis on Ni0.5Zn0.5Fe2O4, whose conversions were of 91.4 % in methyl esters and of 77.8 % in ethyl esters, while the Ni0.2Cu0.3Zn0.5Fe2O4 sample showed conversion of 75.1 and 65.1 %, respectively. The conversions in the methyl and ethyl transesterification were of 14 and 2 % of the Ni0.5Zn0.5Fe2O4 sample, and of 11 and 3 % for the Ni0.2Cu0.3Zn0.5Fe2O4 sample.

This study was carried out to synthesize, characterize and evaluate the application of mesoestruturated catalysts MCM-41, 5%MoO3-MCM-41 and 5%NiO-MCM-41 in the hydrolysis of microcrystalline cellulose. XRD results indicate that the phase of mesoporous MCM-41 was obtained and that the introduction of metal oxides did not affect this mesoporous phase. About the heterogeneous hydrolysis reaction, it was observed that the increase in temperature results in a higher concentration of glucose and the catalyst 5%MoO3-MCM-41 provides the highest concentrations of glucose.

A determinação das isotermas de adsorção de umidade constitui fator essencial nos projetos e estudos de sistemas de secagem, processamento, armazenagem, embalagem e predição tempo de prateleira de produtos alimentícios. A obtenção das isotermas dar-se por meio da variação do conteúdo de umidade de equilíbrio em função da atividade de água a uma dada temperatura constante. A predição das curvas das isotermas é realizada por meio da aplicação de modelos matemáticos aos dados experimentais. Através das isotermas de adsorção podem ser calculadas propriedades termodinâmicas, como o calor isostérico de adsorção, que é utilizado na análise, desenvolvimento de processos alimentícios e estudo das interações umidade-sólido. Assim, desenvolveu-se o presente estudo com o objetivo de estudar o comportamento das isotermas de adsorção da folha e do caule de coentro desidratados, definir o modelo que melhor representa o comportamento das curvas e determinar o comportamento do calor isostérico de adsorção. Os dados experimentais obtidos foram ajustados por regressão não linear, pelos modelos de GAB, Oswin, Smith, BET, Peleg e Halsey. Os modelos que melhor representaram o comportamento das curvas de adsorção da folha e do caule foram os de Smith e Peleg. O calor isostérico de adsorção obtido para folha desidratada é maior que o do caule.

The determination of adsorption isotherms of moisture is an essential factor in the projects and studies of systems for drying, processing, storage, packaging and shelf-time prediction of food products. The adsorption isotherms are obtained by means of variation of moisture content in terms of equilibrium water activity at a constant temperature, and its prediction is performed by the application of mathematical models to experimental data. Through the adsorption isotherms it can be calculated some thermodynamic properties such as isosteric heat of adsorption, which is used in the analysis, development of case study of food and moisture-solid interactions. Thus, this work aimed to study the behavior of adsorption isotherms of leaves and stems of dehydrate coriander, evaluate the model that represents the behavior of the curves and determine the isosteric heat of adsorption. The experimental data were fitted by nonlinear regression, the GAB, Oswin, Smith, BET, Halsey and Peleg models had been used. The models which best represented the behavior of the adsorption curves of the leaf and stem were from Smith and Peleg. The isosteric heat of adsorption obtained from dried leaf is larger than the stem.

Objetivou-se, no presente trabalho, estudar a cinética de secagem da polpa de tamarindo pelo método de camada de espuma (foam-mat), a 50, 60, 70 e 80 ºC, e avaliar o efeito dessas temperaturas no teor de ácido ascórbico, acidez total titulável e na cor, expressa pelo parâmetro luminosidade (L*) matiz (hº). Para a representação dos dados experimentais da secagem, três modelos matemáticos de camada fina foram aplicados adotando-se como critérios de seleção o coeficiente de determinação (R²) e o desvio quadrático médio (DQM). De acordo com os resultados obtidos, tem-se que a temperatura é um fator determinante no processo de desidratação e que o modelo de Midilli e Kucuk foi o que melhor representa o comportamento das curvas de desidratação. Os melhores resultados para o teor de ácido ascórbico, acidez titulável e cor foram obtidos para as temperaturas de 60 e 70 ºC.

The foam-mat drying process was studied for the tamarind pulp at 50, 60, 70 and 80ºC and the temperature effect on the tamarind powder were evaluated as regards to ascorbic acid content, total titratable acidity and colour, expressed by luminosity (L*) and hue (hº). For the representation of the drying process three models for thin-layer were applied and the criterion of evaluation used were the coefficient of determination (R²) and root mean square error (DQM). According to the results the temperature is a determinant parameter in the drying process, and the Midilli and Kucuk model was the best one to represent the behavior of the drying curves. The best results for ascorbic acid content, titritable acidity and colour were obtained at the temperatures of 60 and 70 ºC.