La guanábana (Annona muricata L.) es una fruta tropical perecedera y de gran valor nutricional. El objetivo de éste trabajo fue evaluar la termodinámica de sorción de polvos guanábana con maltodextrina (MD) obtenidos por diferentes tecnologías de secado, lo que permite la comprensión de los mecanismos que regulan este proceso. Se determinaron las isotermas de adsorción por método gravimétrico estático a 20, 30, 40 y 50 °C, para polvos secados por liofilización (FD), aspersión (SD) y vacío (VD). Los resultados mostraron que el modelo de GAB se ajustó a los datos experimentales de adsorción (R²>0,9893). Se mostró la influencia del sistema de secado en los parámetros del modelo. Los valores de humedad de la monocapa, entre 5,28 y 9,30% (kg de agua/kg s.s), se encuentran dentro de los rangos reportados para alimentos deshidratados.

The soursop (Annona muricata L.) is a perishable tropical fruit with high nutritional value. The aim of this work was to evaluate the sorption thermodynamics of soursop powders with maltodextrin (MD), obtained by different drying technologies, thus allowing understanding the mechanisms that govern this process. Adsorption isotherms of freeze dried (FD), spray drying (SD) and vacuum drying (VD) powders were determined at 20, 30, 40 and 50 °C by using the static gravimetric method. The results showed that the better fits the adsorption experimental data is the GAB model (R²>0.9893). The influence of the drying system in the model parameters was also shown. The monolayer moisture values between 5.28 and 9.30% (kg water/kg d.s) were within the reported range for dehydrated food.

As propriedades reológicas e termofísicas foram determinadas para suco de amora produzido a partir da fruta com 9.1 ± 0.5 °Brix e densidade de 1,0334 ± 0,0043 g cm-3. O processo de concentração foi realizado utilizando-se um roto evaporador, sob vácuo, obtendo-se o suco concentrado em aproximadamente 60 °Brix. As diferentes concentrações foram obtidas a partir da diluição do suco concentrado em água destilada. As medidas reológicas foram conduzidas utilizando-se o reômetro Rheotest 2.1 do tipo Searle. Em todos os experimentos as amostras apresentaram um comportamento pseudoplástico, e o modelo da Lei da Potência foi ajustado satisfatoriamente aos dados experimentais. O fator de atrito foi medido para o suco em regime laminar com comportamento pseudoplástico. A condutividade térmica, a difusividade térmica e a densidade foram determinadas em triplicata para o suco de amora nas faixas de 9,4 a 58,4 °Brix e de 0,5 a 80,8 °C. A temperatura e a concentração mostraram forte influência nas propriedades termofísicas do suco de amora. Os valores do calor específico aparente variaram de 2,416 a 4,300 kJ.kg-1 °C.

Rheological and thermophysical properties were determined for blackberry juice, which was produced from blackberry fruit at 9.1 ± 0.5 °Brix and density of 1.0334 ± 0.0043 g cm-3. The concentration process was performed using a roto evaporator, under vacuum, to obtain concentrated juice at about 60 °Brix. In order to obtain different concentrations, concentrated juice was diluted with distilled water. Rheological measurements were carried out using a Rheotest 2.1 Searle type rheometer. In the tested ranges, the samples behaved as pseudoplastic fluids, and the Power-Law model was satisfactorily fitted to the experimental data. The friction factor was measured for blackberry juice in laminar flow conditions of pseudoplastic behavior. Thermal conductivity, thermal diffusivity and density of blackberry juice at 9.4 to 58.4 °Brix were determined, in triplicate, at 0.5 to 80.8 °C. Polynomial regression was performed to fit experimental data obtaining a good fit. Both temperature and concentration showed a strong influence on thermophysical properties of blackberry juice. Calculated apparent specific heat values varied from 2.416 to 4.300 kJ.kg-1 °C in the studied interval.