Prediction of the effect of temperature on water sorption isotherms of food material (original) (raw)
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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.
New BET Type Multilayer Sorption Isotherms. Part II: Modelling Water Sorption in Foods
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The aim of the present work is to solve the dilemma about the dierences between the values of the monolayer and the energy parameters obtained by the regression of water sorption data by foods and foodstus using the Brunauer, Emmett and Teller (BET) two-parameter isotherm or the Guggenheim, Anderson and de Boer (GAB) three-parameter isotherm. It is shown that the GAB values are more general and have more physical meaning, and that the two BET parameters can be calculated in terms of the three GAB-parameters. Furthermore, the marked dependency of the BET constants on the regression range as well as the typical upswing at higher water activities observed in the so-called BET plots are explained. It is also shown that the rough agreement early reported by L. Pauling, J. Am. Chem. Soc. 67 (1945) 555±557 between monolayer values and number of polar groups in the aminoacid side chain in several proteins is enhanced if the former are evaluated by means of the GAB sorption equation. Ó
Sorption Isotherms for Food Products: Study of Models Agreement
Boletim do Centro de Pesquisa de Processamento de Alimentos, 2011
The knowledge of sorption isotherms is important for establishing conditions of storage and of processes like drying. There are several models for fitting sorption isotherms. This work presents a study about the agreement of 40 mathematical models of sorption isotherms to experimental data of 53 food products. The quadratic residual sum and the standard error were the criteria of evaluation. For the major part of the products, the best agreement was obtained with equation of Jaafar and Michalowski, if temperature or saturation pressure were not considered as a variable. For cases where temperature or saturation pressure were considered, the equation of Strohman and Yoerger was the one with the best agreement for most of the products. Ross equation, based on thermodynamics aspects, was also tested for some products, but the agreement was just satisfactory.
Physica A: Statistical Mechanics and its Applications, 2015
Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.
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.
Adsorption isotherms of pear at several temperatures
Thermal Science, 2014
The moisture adsorption isotherms of pear were determined at 15°C, 30°C, and 45i°C using the standard static gravimetric method over a range of water activity from 0.112 to 0.920. The experimental data were fitted with isotherm equations recommended in ASAE Standard D245.5. In order to find which equation gives the best results, large number of numerical experiments were performed. After that, several statistical criteria proposed in scientific literature for estimation and selection of the best sorption isotherm equations were used. For each equation and experimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D'Agostino-Pearson test of normality, single-sample run test and significance and precision of the model parameters). The performed statistical analysis shows that the Guggenheim-Anderson-de Boer equation has the highest value of average performance index, but higher correlation between pair of parameters leads to lower precision of estimated parameters.
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.
ADSORPTION ISOTHERMS OF PEAR AT SEVERAL TEMPERATURES by
2016
The moisture adsorption isotherms of pear were determined at 15 °C, 30 °C, and 45i°C using the standard static gravimetric method over a range of water activity from 0.112 to 0.920. The experimental data were fitted with isotherm equations recommended in ASAE Standard D245.5. In order to find which equation gives the best results, large number of numerical experiments were performed. After that, several statistical criteria proposed in scientific literature for estimation and selec-tion of the best sorption isotherm equations were used. For each equation and ex-perimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D'Agostino-Pearson test of normality, single-sample run test and significance and precision of the model parameters). The performed statistical analysis shows that the Guggenheim-Anderson-de Boer equation has the highest value of average per-formance index, but...