Applicability of the generalised D’Arcy and Watt model to description of water sorption on pineapple and other foodstuffs (original) (raw)
Related papers
Analysis of a Model for Water Sorption Phenomena in Foods
Journal of Food Science, 1982
The validity of the physical model on which the Hailwood and Horrobin (Trans. Far. Sot. 42B: 84; 1946) isotherm equation was developed was investigated. The results indicate that although the equation may tit sorption data for almost any type of food, it satisfies thermodynamic requirements (i.e. prediction of the temperature dependence) only for proteins and starchy foods. The results also show that plotting enthalpic changes against entropic changes for water sorption satisfies the enthalpy/entropy compensation phenomenon.
A Model for Describing the Water Sorption Behavior of Foods
Journal of Food Science, 1976
A multilayer adsorption equation, originally developed for physical adsorption on nonuniform surfaces, is used to describe the water sorption behavior of a great variety of foods and food components. Characteristic parameters of the sorption equation, for each of the products tested, were computed. A comparison was made between Halsey's equation and Henderson's classical one. Literature data for 220 food isotherms, comprising 69 different materials, were utilized to compare both equations. It was found that in most cases Halsey's equation has a better fit than Henderson's.
Water desorption thermodynamic properties of pineapple
Journal of Food Engineering, 2007
The water desorption isotherms of pineapple were determined at 5, 15, 25, 35 and 45°C by using a gravimetric technique within the water activity range of 0.1-0.9. The effect of the temperature showed a cross-over of the desorption isotherms at water activity of 0.75. The experimental data was fitted to the GAB model taking into account the effect of the temperature. The obtained simulation could be considered satisfactory (mean relative error <5.0% and percentage of explained variance >99.8%). The net isosteric heat of sorption (Q st n) and the differential entropy (S d) were estimated as functions of the moisture content, the enthalpy-entropy compensation theory was applied to sorption isotherms and plots of Q st vs. S d provided the isokinetic temperature, suggesting an enthalpy controlled sorption process.
Food Research International, 2009
Water sorption on foodstuffs is very important in different areas of food science engineering. However, usually measured range of relative humidity covers only two of three stages of water sorption mechanism i.e. polymolecular sorption and capillary condensation. Since in this range different water sorption models can fit the experimental data well it is hard to decide which model is the most correct. In this study the results of water sorption isotherms measured from low humidity levels on marjoram, dill, granulated garlic, semolina, skim milk powder and ground coffee are reported. They are fitted by the most popular models applied in food science (i.e. proposed by: Halsey, Lewicki, Henderson, Chung and Pfost, Ferro Fontan et al. and Guggenheim, Anderson and de Boer (GAB)). We also extend the study to the newest models successfully applied in food engineering, i.e. the generalized D'Arcy and Watt model (GDW) and the approach of the cooperative multimolecular sorption (CMMS). Finally, we discuss the limits of the models at low humidity levels, the possibility of reduction to Henry's law and we show the advantages and disadvantages of all approaches. It is concluded that among studied models the GDW equation seems to be the best for description of data in the whole range of relative humidity.
Sorption isotherms and heat of sorption of pineapple
Journal of Food Engineering, 2001
Sorption isotherms of pineapple were determined at 20°C, 30°C, 40°C and 50°C temperatures by using dynamic method. Six twoparameter and one three-parameter isotherm models were selected to ®t the observed data, and the modi®ed BET model was found to be the best-®tted model for pineapple. The heat of sorption of pineapple decreased with an increase in moisture content and the heat of sorption was found to be a power function of moisture content. Ó
Adsorption isotherm and heat of sorption of osmotically pretreated and air-dried pineapple slices
European Food Research and Technology, 2004
Slabs (1 1.5 5 cm) of pineapple were immersed in sucrose solutions of 52B, 60B and 68B (w/w) at 25 C for 12 h. Osmosed pineapple slices were subsequently air-dried at 60 C for 72 h. Adsorption isotherms of osmo-dried pineapple slices were determined at 20 C and 40 C, using the gravimetric-static method. Isotherms were modeled using Brunnauer, Emmet and Teller (BET) and Guggenheim Anderson de Boer (GAB) models. Heat of moisture adsorptions were calculated from adsorption data using the Clausius-Clapeyron equation. Adsorption isotherms of osmo-oven-dried pineapple followed the characteristic type III (J-shape) isotherms. Equilibrium moisture contents at constant water activity decreased with increasing temperature, but crossing of the isotherms occurred at a w~0 .86. GAB and BET monolayer moisture decreased with increased temperature. The net isosteric heat increased with decreased moisture content, and decreased with increased sucrose pretreatment concentration of pineapple slices.
A New Model for Predicting Sorption Isotherm of Water in Foods
A new model for predicting sorption isotherms of type II and III based on the Polanyi theory is proposed. This model allows the prediction of the sorption isotherms at different temperatures from one experimental isotherm. The theoretical predictions of isotherms and isosteric heat were validated successfully using data from literature for twenty one foods. This method allows total experimental time and operation costs to be reduced.
Equations for fitting water sorption isotherms of foods: Part 1 - a review
International Journal of Food Science & Technology, 2007
The purpose of the present work is to present a review of literature on equations for fitting water sorption isotherms of foods and food products. Twenty-three equations, which have been proposed in the literature for correlating equilibrium moisture content in food systems, have been compiled and analysed. Their origin, range of applicability (both to type of food and water activity) and use are discussed. It is hoped that this critical compilation may be a useful guide for those researchers interested in the mathematical description of the water sorption isotherms of foods.
Prediction of the effect of temperature on water sorption isotherms of food material
International Journal of Food Science & Technology, 1976
An empirically modified two-parameter multilayer adsorption equation is shown to take into account the effect of temperature on the water sorption isotherms of some food materials. Characteristic parameters of the sorption equation for each food tested are presented. The equation should be of value in predicting the shelf life behaviour of food products at different storage temperatures.