Navegando por Autor "Collazos-Escobar, Gentil Andres"

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Modeling dynamic adsorption isotherms and thermodynamic properties of specialty ground roasted-coffee (Coffea arabica L.)
(Editora UFLA, 2019-01) Collazos-Escobar, Gentil Andres; Gutiérrez-Guzmán, Nelson; Váquiro-Herrera, Henry A.
Specialty coffee is highly differentiated product because of its sensorial attributes: aroma, body and brand reputation. In specialized markets, these products are highly valued, and sometimes up to six times their commercial value is paid. Thus, it is essential to preserve their freshness. Sorption isotherms are necessary for determining and studying water sorption changes in specialty coffee during storage. This study aimed to determine the adsorption isotherms of specialty ground roasted-coffee at temperatures of 25 °C, 30 °C and 40 °C and water activities between 0.1 and 0.8 using the dynamic dewpoint method (DDI). The experiment sorption data were modeled using 12 different equations with non-linear regression to represent the dependence of the equilibrium moisture content with both water activity and temperature. In addition, the thermodynamic properties were determined with the experiment adsorption data. The results showed that type III isotherms were obtained according to the Brunauer classification, and the Weibull equation satisfactorily modeled the effect of the temperature on the hygroscopic equilibrium in the specialty ground roasted-coffee. The results of thermodynamic analysis showed that the net isosteric heat of adsorption and Gibbs free energy decreased as the equilibrium moisture content increased, indicating the amount of energy released, a strong bond energy between water molecules in the product components and spontaneity in the adsorption process. The entropy of the adsorption increased with the moisture content, leading to product stability conditions during storage; it was possible to conclude that to guarantee the stability of high quality, ground, roasted coffee should store in environments where the water activity does not exceed 0.5 at temperatures between 25 °C and 40 °C. The results were similar to those reported for the roasted and ground coffee of others cultivars.
Moisture dynamic sorption isotherms and thermodynamic properties of parchment specialty coffee (Coffea arabica L.)
(Editora UFLA, 2020) Collazos-Escobar, Gentil Andres; Gutiérrez-Guzmán, Nelson; Váquiro-Herrera, Henry Alexander; Amorocho-Cruz, Claudia Milena
Sorption isotherms represent an efficient and valuable tool for predicting the equilibrium moisture content of foods under different humidities and temperatures; thus, they are useful for determining shelf-life and safe storage conditions. The aims of this study were to determine the sorption isotherms of parchment specialty coffee at water activity values of 0.1−0.8 and temperatures of 25, 30, and 40 °C using the dynamic dew point method. The experimental sorption data were modeled using 12 different equations to represent the dependence of equilibrium moisture content on water activity and temperature. Thermodynamic properties were also obtained from the experimental data. The results showed a type II sigmoid shape according to Brunauer-Emmett-Teller (BET) classification, and the double log polynomial (DLP) equation successfully modeled the effects of temperature on the sorption isotherms, obtaining a good fit (R2 adj = 0.99 and RMSE = 0.1 % dry basis). The dynamic dewpoint isotherm (DDI) method was advantageous for modelling due to its high availability of experimental data. Thermodynamic analyses showed that the net isosteric heat of sorption, Gibbs free energy, and sorption entropy decreased as equilibrium moisture content increased, and the compensation theory provided evidence that the sorption process was controlled by enthalpy (Tβ > Thm).