The osmotic dehydration pre-treatment is used to partially reduce the fruit initial water content, before convective drying. Purpose of the present work is to investigate the influence of osmotic treatment followed by convective drying on the physicochemical parameters of guava slices. The Paluma guava was cut into slices of 3.0 × 2.0 × 0.9 cm, dehydrated and dipped in sucrose syrup at concentrations of 40, 50 and 60 °Brix, at temperatures of 30, 40 and 50 °C. The process was again supplemented by convective drying at temperatures of 50, 60 and 70 °C. Guava-raisins with and without pre-osmotic treatments were subjected to the following physico-chemical analyzes: soluble solids, pH, total acidity, ash, reducing and total sugars, water activity (A w ). The color was considerably changed into a darker and the total sugar reduced as a result of the syrup concentration and osmotic dehydration temperatures. Also, the pH and A w decreased through application of treatments. From the results it is recommended that the production of guava passes under dehydrating conditions of 60 °Brix at 50 °C and further drying temperature of 60 ° C is efficient.
A cinética de desidratação osmótica é uma técnica comumente utilizado no processamento de frutas imersas em soluções de sacarose concentradas sob diferentes temperaturas. O presente trabalho teve como objetivo estudar a cinética de desidratação osmótica de fatias circulares de banana Pacovan com casca, a 5 mm de espessura, submetidas às temperaturas de 40 e 70 °C, com solução de sacarose nas concentrações de 40, 50 e 60 °Brix. Acompanhadas no período de 4 horas e as condições de equilíbrio foram determinadas após 24 horas de imersão. A perda de água e ganho de sacarose durante a desidratação osmótica foram ajustados aos modelos de Lewis, Henderson e Pabis, Page, Peleg e Silva et alii, através do programa LAB Fit para descrever o processo, e os melhores indicadores estatísticos foram obtidos com os modelos de Peleg e Silva et alii, para descrever o fenômeno de transferência de água, já os modelos de Page e Peleg descrevem satisfatoriamente o ganho de sacarose. A inspeção gráfica da quantidade de água (e de sacarose) indicou que a remoção de aproximadamente 80% de água contida no produto ocorreu em até 800 min. A análise das superfícies de resposta obtidas em 800 min revelou que o tratamento a 70 °C e 60 °Brix foi o responsável pela maior perda de água e ganho de sacarose.
In this study, mass transfer simulations were performed during the process of osmotic dehydration of green beans in NaCl solutions of 20 and 26.5% at 50 °C. Additionally, the effect of solute concentration on boundary conditions was investigated. For such, a diffusion modelassuming constant diffusivity -and the geometry of an infinite cylinder was considered. A numerical solution was also developed and coupled with an optimizer in order to obtain the process parameters using experimental data. The results were consistent with those mentioned in the literature, for which analytical tools were utilized to describe the process.
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