Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.)
Antonio Vega-Gálvez1, Jessica López1, Kong Ah-Hen2*, María José Torres1 and Roberto Lemus-Mondaca1
1Food Engineering Department, La Serena University, Raúl Bitrán Avenue, La Serena, Region of Coquimbo, Chile
2Institute of Food Science and Technology, Austral University of Chile, Julio Sarrazín Avenue, Valdivia, Region de los Ríos, Chile
Article history:
Received March 26, 2013
Accepted October 1, 2013
Key words:
Cape gooseberry, sorption isotherm, modelling, isosteric heat, glass transition temperature, Gordon-Taylor model
Summary:
Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L.) were determined at three temperatures (20, 40 and 60 ºC) using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson-De Boer (GAB), Brunauer-Emmett-Teller (BET), Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg) of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.
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