Sorption Isosteric Heat Determination by Thermal Analysis and Sorption Isotherms

A procedure based on thermal analysis thermogravimetry (TG) and differential-scanning calorimetry (DSC) was examined to compute isosteric heat of sorption for water. DSC measurements on samples with different moisture content allowed determining enthalpy variations due to water vaporization. Thermogravimetries performed on the same samples enabled a link to be made between enthalpic measurements and weight losses and thus compute isosteric heats. The procedure was applied to cauliflower and potato starch. From equilibrium isotherms by applying the Clausius-Clapeyron equation, the isosteric heats of sorption were calculated. The comparison of the values obtained through both procedures showed a good agreement.

[1]  Theodore P. Labuza,et al.  Evaluation of food moisture sorption isotherm equations part I: Fruit, vegetable and meat products , 1985 .

[2]  G. Robertson,et al.  Comparison of regression methods for fitting the GAB model to the moisture isotherms of some dried fruit and vegetables , 1991 .

[3]  W. Wolf,et al.  Standardization of Isotherm Measurements (Cost-Project 90 and 90 BIS) , 1985 .

[4]  J. Chirife,et al.  On the Temperature Dependence of Isosteric Heats of Water Sorption in Dehydrated Foods , 1989 .

[5]  J. Chirife,et al.  Isosteric heats of water vapor sorption on dehydrated foods. I. analysis of the differential heat curves , 1976 .

[6]  C. Suárez,et al.  Heats and Entropies of Sorption of Cereal Grains : A Comparison Between Integral and Differential Quantities , 1997 .

[7]  W. Mcminn,et al.  MOISTURE SORPTION CHARACTERISTICS OF STARCH MATERIALS , 1997 .

[8]  L. Greenspan.  Humidity Fixed Points of Binary Saturated Aqueous Solutions , 1977, Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry.

[9]  E. Tsami.  Net isosteric heat of sorption in dried fruits , 1991 .

[10]  J. Chirife,et al.  Estimation of the precision of isosteric heats of sorption determined from the temperature dependence of food isotherms , 1992 .

[11]  A. Raemy,et al.  Thermal behaviour of carbohydrates studied by heat flow calorimetry , 1983 .

[12]  J. G. Brennan,et al.  Moisture sorption isotherm characteristics of potatoes at four temperatures , 1991 .

[13]  R. B. Duckworth,et al.  The water-vapour sorption isotherms of microcrystalline cellulose (MCC) and of purified potato starch. Results of a collaborative study , 1984 .

[14]  S. Simal,et al.  Calorimetric Techniques Applied to the Determination of Isosteric Heat of Desorption for Potato , 1997 .