Isotermas dinámicas de sorción de humedad y propiedades termodinámicas de café soluble

Studying the moisture sorption behavior and thermodynamic properties of dehydrated foods provides important information for the design of drying and storage processes that ensure the stability of food products. The purpose of this work was to obtain the dynamic moisture isotherms, model their behavior and determine the thermodynamic properties for soluble coffee. The isotherms were obtained by dynamic dew point method (DDI) at 20, 25, 35 and 40 °C within a range of water activity (aw) of 0.10-0.90. The soluble coffee sorption isotherms exhibited type III behavior. The best fit of the experimental data was obtained with Peleg equation in the range of temperatures and aw investigated. Moisture content increased with increasing temperature in the range of 0.25-0.65 aw. The moisture content of the monolayer (MO), of the Brunauer-Emmett-Teller (BET) model, decreased with increasing temperature, as did the surface area of soluble coffee. Thermodynamic properties such as net isosteric heat of sorption, enthalpy of sorption, and Gibbs free energy of sorption were determined from the isotherm data. Net isosteric heat and entropy of sorption decreased with increasing moisture content. The Gibbs free energy of adsorption changed from -4906 to -225 J mol-1 and decreased with increasing moisture.Estudiar el comportamiento de sorción de humedad y propiedades termodinámicas de alimentos deshidratados proporciona información importante para el diseño de procesos de secado y almacenamiento que aseguren la estabilidad de los productos. El propósito de este trabajo fue obtener las isotermas dinámicas de humedad, modelar su comportamiento y determinar las propiedades termodinámicas para café soluble. Las isotermas fueron obtenidas por el método dinámico de punto de roció (DDI) a 20, 25, 35 y 40 °C dentro de un rango de actividad de agua (aw) de 0.10-0.90.  Las isotermas de sorción de café soluble exhibieron un comportamiento tipo III. El mejor ajuste de los datos experimentales se obtuvo con la ecuación de Peleg en el rango de temperaturas y aw investigadas. El contenido de humedad aumento con el incremento de la temperatura en el rango de 0.25-0.65 aw. El contenido de humedad de la monocapa (MO), del modelo de Brunauer-Emmett-Teller (BET), disminuyó con el incremento de la temperatura, al igual que el área superficial del café soluble. Propiedades termodinámicas como calor isostérico neto de sorción, entalpia de sorción y energía libre de Gibbs de sorción se determinaron a partir de los datos de las isotermas encontradas. El calor isostérico neto de sorción y la entropía disminuyeron al aumentar el contenido de humedad. La energía libre de Gibbs de adsorción cambió de -4906 a -225 J mol-1 y se redujo con el incremento de la humedad

Vaccinium meridionale Swartz Supercritical CO2 Extraction: Effect of Process Conditions and Scaling Up

Vaccinium meridionale Swartz (Mortiño or Colombian blueberry) is one of the Vaccinium species abundantly found across the Colombian mountains, which are characterized by high contents of polyphenolic compounds (anthocyanins and flavonoids). The supercritical fluid extraction (SFE) of Vaccinium species has mainly focused on the study of V. myrtillus L. (blueberry). In this work, the SFE of Mortiño fruit from Colombia was studied in a small-scale extraction cell (273 cm3) and different extraction pressures (20 and 30 MPa) and temperatures (313 and 343 K) were investigated. Then, process scaling-up to a larger extraction cell (1350 cm3) was analyzed using well-known semi-empirical engineering approaches. The Broken and Intact Cell (BIC) model was adjusted to represent the kinetic behavior of the low-scale extraction and to simulate the large-scale conditions. Extraction yields obtained were in the range 0.1%–3.2%. Most of the Mortiño solutes are readily accessible and, thus, 92% of the extractable material was recovered in around 30 min. The constant CO2 residence time criterion produced excellent results regarding the small-scale kinetic curve according to the BIC model, and this conclusion was experimentally validated in large-scale kinetic experiments