Cinética de reidratação e comportamento reológico de blackberries desidratadas

Abstract

Blackberry in natura is a fruit that has a relatively short shelf life, so the drying process is used to preserve the product for a longer period of time. To reconstitute this product the process the rehydration process is effected. The study of this operation and of rheological behavior is of paramount importance as it provides information on the physical and chemical changes resulting from its processing. This work aimed to study the rehydration kinetics of blackberries in water (10 ± 2, 29 ± 2 cC and 45 ± 2 cC/45 mim) and in milk leite ( 10 ± 2 CC e 29 ± 2 ti 45 min), as well as to evaluate the rheological behavior of suspensions of blackberries after rehydration in water (45 mim), in different concentrations of solids at different temperatures and determine the physico-chemical characteristics and the texture profile of dehydrated blackberries and after rehydration in water and milk (29 t/45 min). The water and milk diffusion coefficients were determined by the Fick Law model, obtaining values 8,60.10-5 between 2,53.104 cm2- mim. The coefficients of water and milk diffusion when correlated with the same rehydration temperatures did not show significant differences between the average.To describe the kinetics of rehydration, 12 mathematical models were used. For blackberries rehydrated in water the diffusion approximation model was the best fit for the experimental data, with R2 = 0,98 e 1,00 and at 45 °C was the Logari thmic model, with R2 = 0.99. The blackberries rehydrated in milk at 10 °C the Verma model was the one that best fit the experimental data, with R2 = 0.99 and at 29 ° C was the Logarithmic model, with R2 = 0.99. To study the rheological behavior of blackberry suspensions, six mathematical models were used and to verify the influence of analysis temperature and solids concentration on rheological behavior of berries suspensions, was used a 22 factorial design with three central points. For the 10% solids suspension at 20 ° C and the 60 °C, the Casson model was the best fit for the experimental data, with R2 = 0.99 and 0.9. The Solid suspensions at the three central points (20% at 40 °C) and 30% at 20 °C did not satisfactorily adjust the experimental data. At 30% at 60 ° C, the Ostwald de Waellese model fitted reasonably, with R2 = 0.80. In this study, it was not possible to analyze the factorial design, as no model fit well for all the tests. Regarding the texture profile, it was verified that the adhesiveness of rehydrated blackberries was significantly lower, when compared to the berries in the dehydrated form, possibly as a consequence of the transfer of solvent (water or milk) to the fruits and leaching of solids to the médium. The resilience of dehydrated blackberries was significantly lower when correlated with rehydrated berries.