Thermodynamic properties of moisture sorption of potato

Abstract The moisture sorption isotherms of potato were determined using a gravimetric static method at 30, 45 and 60 °C, and over a range of relative humidities. The isotherms exhibited Type II behaviour, with the sorption capacity decreased with increasing temperature. The Guggenheim–Anderson–de Boer (GAB) and Halsey models were found to adequately describe the sorption characteristics. Calculation of the thermodynamic properties (differential enthalpy, integral enthalpy, differential entropy and integral entrophy) was further used to provide an understanding of the properties of water and energy requirements associated with the sorption behaviour. Isosteric heats (differential enthalpies) were calculated through direct use of moisture isotherms by applying the Clausisus–Clapeyron equation. The differential enthalpy and entropy decreased with increasing moisture content and were adequately characterised by a power law model. A plot of differential heat versus entropy satisfied the enthalpy–entropy compensation theory. The spreading pressures (adsorption and desorption) increased with increasing water activity, and decreased with increasing temperature. The net integral enthalpy increased with moisture content to a maximum value (around the monolayer moisture content) and then decreased. In a reverse manner, the net integral entropy decreased with moisture content to a minimum value and then increased.

[1]  N. Aviara,et al.  Thermodynamics of moisture sorption in melon seed and cassava , 2002 .

[2]  R. Tyler,et al.  THERMODYNAMICS OF MOISTURE SORPTION IN ALFALFA PELLETS , 1997 .

[3]  C. Suárez,et al.  Enthalpy‐Entropy Compensation in Sorption Phenomena: Application to the Prediction of the Effect of Temperature on Food Isotherms , 1986 .

[4]  D. Simatos,et al.  Properties of Water in Foods , 1985 .

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

[6]  N. Sanjuán,et al.  Equilibrium isotherms and isosteric heats of morel (Morchella esculenta) , 2002 .

[7]  W. G. Hunter,et al.  Enthalpy-entropy compensation. 1. Some fundamental statistical problems associated with the analysis of van't Hoff and Arrhenius data , 1976 .

[8]  R. V. Morey,et al.  Comparison of four EMC/ERH equations , 1989 .

[9]  R. Tyler,et al.  THERMODYNAMICS OF MOISTURE SORPTION IN WINGED BEAN SEED AND GARI , 1999 .

[10]  W. G. Hunter,et al.  Enthalpy-entropy compensation. 2. Separation of the chemical from the statistical effect , 1976 .

[11]  G. Halsey,et al.  Physical Adsorption on Non‐Uniform Surfaces , 1948 .

[12]  S. Rizvi,et al.  Thermodynamic properties of dehydrated foods , 1984 .

[13]  P. S. Madamba,et al.  Enthalpy-entropy compensation models for sorption and browning of garlic , 1996 .

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

[15]  C. V. D. Berg.  Development of B.E.T.-Like Models for Sorption of Water on Foods, Theory and Relevance , 1985 .

[16]  M. B. San Martín,et al.  MODELLING ADSORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF ROUGH RICE , 2001 .

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

[18]  M. Mondol,et al.  Sorption isotherms and heat of sorption of pineapple , 2001 .

[19]  G. Mazza,et al.  Water Sorption Properties of Yellow Globe Onion (Allium cepa L.) , 1978 .

[20]  S. Bruin,et al.  Water activity and its estimation in food systems: theoretical aspects , 1978 .

[21]  W. Horwitz.  Official Methods of Analysis , 1980 .

[22]  F. Kaymak-Ertekin,et al.  Moisture sorption isotherm characteristics of peppers , 2001 .

[23]  J. Chirife,et al.  Thermodynamics of water vapour sorption by sugar beet root , 1976 .