Equilibrium Moisture Characteristics of Raw and Parboiled Paddy, Brown Rice, and Bran

Equilibrium moisture content (EMC) of raw and parboiled paddy, brown rice, and bran were obtained by equilibrating them at 20-80% equilibrium relative humidity (ERH) at 13, 30, and 40°C above saturated inorganic salt solutions. Four EMC-ERH models namely modified Henderson, modified Chung-Pfost, modified Halsey, and GAB were fitted to the observed data and were evaluated using mean relative percent error, standard error of estimate and residual plots. At a constant relative humidity, equilibrium moisture content decreased with increasing temperature. The GAB model described the EMC data the best, modified Henderson and modified Chung-Pfost equations gave good fit while the modified Halsey model gave a poor fit. The heat of vaporization (h_fg) of raw and parboiled paddy at different grain moisture contents and temperatures was estimated from EMC data and using the Clausius-Clapeyron equation.     

Sorption Isotherms of Vaccum-Fried Carrot Chips

The moisture sorption isotherms for carrot chips after vacuum frying were determined using a gravimetric technique at 10, 25, and 40°C and fitted with BET, GAB, Smith, Halsey, Henderson, and Peleg models. A nonlinear least-squares regression program was used to determine the models constants. The Peleg, Halsey, and GAB models were found to best represent the experimental data throughout the entire water activity range.     

ADSORPTION ISOTHERMS OF RAW AND ROASTED HAZELNUTS

Adsorption isotherms of raw and roasted (at 100°C, 120°C, 140°C and 160°C) hazelnuts of Tombul variety were determined at 25°C, and over relative humidities ranging from 11 to 90% using the gravimetric static method. Eleven sorption models (GAB, BET, Modified BET, Halsey, Iglesias-Chirife, Oswin, Chung-Pfost, Smith, Kuhn, Harkins-Jura and Caurie) were evaluated by using the linear regression method. GAB (Guggenheim-Anderson-de Boer) model satisfactorily described adsorption characteristics of the samples over the experimental range of study. Monolayer values at 25°C were estimated from the GAB model as 0.0155 kg water/kg dry solid for raw and 0.0100-0.0163 kg water/kg dry solid for roasted hazelnuts. Caurie security moisture content for raw hazelnuts was also determined from Caurie model as 0.048 kg water/kg dry solid.     

DESORPTION ISOTHERMS OF WATER IN TRIFOLIATE YAM )Dioscorea dumetorum Pax.(

Desorption isotherms of water in trifoliate yam (Dioscorea dumetorum Pax) were determined using a dynamic gravimetric method at temperatures of 20°, 34°, 46° and 62°C, in the relative humidity range from 11 to 86% A nonlinear least squares regression program was used to fit the measured data to the Modified Henderson, the Modified Halsey, the Chung-Pfost, and the GAB sorption models. The GAB model gave the best fit. The net isosteric heat of sorption, estimated using the Clasius-Clapeyron equation, ranged from 1412 kJ/kg at a moisture content of 0.05 kg/kg, dry basis, to 325 kJ/kg at 0.20 kg/kg. Results obtained in this study should be important in controlling the water content of yam during processing, handling, packaging and storage.     

Modeling of Sorption Isotherms of Various Kinds of Wood at Different Temperature Conditions

Adsorption and desorption isotherms of pine, spruce, birch, and willow Salix viminalis v. Orm (2-year stem) under three temperature conditions (20, 50, 75°C) in the range of water activity 0.0-0.9 were studied. In order to describe our experimental data, five models were implemented (GAB, Peleg, Chung-Pfost, Oswin, Halsey) and compared. It was found that GAB and Peleg models provide the best fit to the experimental data. On the basis of GAB modeling, the monolayer moisture content for each kind of wood was calculated. Moreover, the hysteresis phenomenon was investigated. The influence of temperature and wood variety on sorption isotherms was also tested.     

HEAT CONDUCTION

Abstract

Equilibrium moisture content (EMC) of raw and parboiled paddy, brown rice, and bran were obtained by equilibrating them at 20–80% equilibrium relative humidity (ERH) at 13, 30, and 40°C above saturated inorganic salt solutions. Four EMC-ERH models namely modified Henderson, modified Chung-Pfost, modified Halsey, and GAB were fitted to the observed data and were evaluated using mean relative percent error, standard error of estimate and residual plots. At a constant relative humidity, equilibrium moisture content decreased with increasing temperature. The GAB model described the EMC data the best, modified Henderson and modified Chung-Pfost equations gave good fit while the modified Halsey model gave a poor fit. The heat of vaporization (h _fg) of raw and parboiled paddy at different grain moisture contents and temperatures was estimated from EMC data and using the Clausius–Clapeyron equation.     

MODELING WATER SORPTION IN OKARA SOY MILK

Moisture sorption isotherms of okara soy milk were determined using the gravimetric method in the range 20 - 50 °C. The sorption isotherms exhibited hysteresis along all the water activity range (0·1 - 0·9). The amount of sorbed water increased as the temperature was decreased. The GAB and Halsey models gave a good fit for okara isotherms over the range of water activity 0·1 - 0·9. As temperature increased, GAB k-values increased towards unity where the GAB equation reduces to the BET equation. The influence of temperature on the constants of GAB and Halsey models was evaluated through Arrhenius-type equations. The Clausius Clapeyron equation was used to estimate the isosteric heats of sorption.     

MODELLING ADSORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF ROUGH RICE

Equilibrium Moisture Content (EMC) data for medium rough rice grain, Lido variety were obtained by equilibrating rice samples at different Equilibrium Relative Humidities (ERH) and Temperatures. The employed models to fit the data were GAB, modified Chung-Pfost, modified Halsey, Modified Henderson, and modified Oswin. The data were evaluated using the standard error of moisture content, mean relative standard error (%P) of the model and the correlation coefficient r². The GAB model by indirect regression described the EMC the best, however its parameters lacked of physical meaning. The modified Chung-Pfost and modified Henderson equations presented a similar fit of the EMCERH relationships. The modified Chung-Pfost equation had lower residual values than the modified Henderson equation and was considered the best model to explain the EMC-ERH relationships.     

MODELING OF DESORPTION ISOTHERM OF BLACK TEA

In this paper the relationship between the moisture content of black tea and the relative humidity at different temperature conditions is interrogated. The equivalent moisture contents was measured using the static gravimetric method under the relative humidity range of 10% to 90% and under the temperature range of 25°C to 80°C. The obtained data was analysed using statistical data processing techniques and the results fitted to the different sorption isotherm equations like GAB, Oswin, Henderson, and Halsey at various temperatures. The G.A.B. and Oswin equations show good agreements with the obtained results. The results indicate that the desorption isotherms of black tea are sensitive to the temperature. At constant water activity, an increase in temperature decreases the equivalent moisture content of black tea.     

Sorption Isotherms of Vaccum-Fried Carrot Chips

Abstract

The moisture sorption isotherms for carrot chips after vacuum frying were determined using a gravimetric technique at 10, 25, and 40°C and fitted with BET, GAB, Smith, Halsey, Henderson, and Peleg models. A nonlinear least-squares regression program was used to determine the models constants. The Peleg, Halsey, and GAB models were found to best represent the experimental data throughout the entire water activity range.     

WATER SORPTION ISOTHERMS OF FREEZE DRIED FISH SARDINES

Water sorption isotherms of freeze dried fish sardines were determined at 25, 40 and 50°C using an isopiestic method. Water sorption modeling was carried out using the five parameter Guggenheim-Anderson-deBoer (GAB) equation. The GAB equation was able to predict equilibrium moisture content (EMC) with a mean relative error of 7.4%. The correlation coefficient (R²) of the relationship between the actual and predicted values of EMC was 0.986. Modeling with GAB equation predicted monolayer moisture content (X_m) of 4.94% (d.b.). Net isosteric heat of sorption, determined using Clausius-Clapeyron equation, varied from 12.07 to 0.86 kJ/mol asmois ture content changed from 2.76 to 37.5% dry basis (d.b). Chemical composition analysis showed that fish sardine contained 71% (d.b.) crude protein, 10% (d.b.) fat and 15% (d.b.) ash.     

MODELLING ADSORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF ROUGH RICE

Equilibrium Moisture Content (EMC) data for medium rough rice grain, Lido variety were obtained by equilibrating rice samples at different Equilibrium Relative Humidities (ERH) and Temperatures. The employed models to fit the data were GAB, modified Chung-Pfost, modified Halsey, Modified Henderson, and modified Oswin. The data were evaluated using the standard error of moisture content, mean relative standard error (%P) of the model and the correlation coefficient r². The GAB model by indirect regression described the EMC the best, however its parameters lacked of physical meaning. The modified Chung-Pfost and modified Henderson equations presented a similar fit of the EMCERH relationships. The modified Chung-Pfost equation had lower residual values than the modified Henderson equation and was considered the best model to explain the EMC-ERH relationships.     

EFFECT OF DRYING METHODS ON MOISTURE SORPTION ISOTHERMS OF FUFU AT THREE TEMPERATURES

Moisture sorption characteristics for dried fufu using three drying methods at 25°C, 32°C and 45°C were determined experimentally for water activity ranging from 0.11 to 0.96. At a given temperature and water activity, the rotary dried fufu had the highest equilibrium moisture content while the sun dried had the lowest.

Four linear and four nonlinear sorption models were used to analyze the data. The linear GAB model showed the best fit while the nonlinear Bradley model was the best over the whole range of water activity in their respective groups. Also estimates of the net isosteric heats of sorption and their dependence on moisture content were presented for each product.     

Moisture Adsorption Isotherms of Watermelon Seed and Kernels

The moisture adsorption isotherms of watermelon seeds and kernels from Citrullus lanatus Cv Mateera and Citrullus vulgaris Cv Sugar baby were obtained using standard static method with saturated salt solutions over a range of water activities from 0.113 to 0.92 at 20-60°C. The adsorption capacity of seeds decreased with the increase in temperature at constant water activity. Sorption models were used to explain the adsorption behavior involving water activity and moisture content (Type I) and also temperature (Type II). Oswin's models gave best fit among Type I with coefficient of determination of 0.953-0.995, standard error of 0.031-0.0571, mean relative error of 0.071-0.152, and scattered residual plots. Modified Oswin was the best fit model among Type II for the seeds and kernels of both the cultivars with coefficient of determination of 0.997-0.999, standard error of 0.151-0.255, mean relative error of 0.018-0.244, and scattered residual plots. The net isoelectric heat of adsorption, estimated from Clausius-Clapeyron decreased from about 27.0 to 0.5 kJ/mol in kernels and 18.0 to 0.5 kJ/mol in seeds of both the cultivars as the moisture content increased from 5 to 25% (dry basis).     

Determination of EMC isotherms and appropriate mathematical models for canola

Canola seed needs to be dried to minimize damage during subsequent unit operations. In order to optimize the drying and storage processes of seeds it is necessary to know the equilibrium moisture content at different air equilibrium relative humidities and temperatures. In the present work adsorption equilibrium moisture content isotherms were determined for a specific local canola variety at 25, 40 and 55 °C and seven air relative humidifies within the range of 11-90%. Experimental data were used to model the adsorption isotherm process using non-linear regression analysis. Thirteen available mathematical and semi empirical models were employed to find the best fit isotherm curve model. The Halsey model showed the best results at 25 and 40 °C and the values of coefficient of determination (R²), chi-square (χ²) and root of mean square error (RMSE) were 0.993, 0.122 and 0.295 at 25 °C and 0.994, 0.042 and 0.174 at 40 °C. Another best fit mode was the GAB model at 55 °C which resulted in the values of 0.997, 0.023 and 0.120 for R², χ² and RMSE respectively. The adsorption monolayer moisture content (m₀) was also evaluated using BET equation. The m₀ values at 25 °C, 40 °C and 55 °C were 0.017, 0.016 and 0.015 g H₂O/g solid and the corresponding constant values of the BET equation were found to be −4.733, −5.129 and −10.299 respectively.     

Modeling of Sorption Isotherms of Various Kinds of Wood at Different Temperature Conditions

Adsorption and desorption isotherms of pine, spruce, birch, and willow Salix viminalis v. Orm (2-year stem) under three temperature conditions (20, 50, 75°C) in the range of water activity 0.0–0.9 were studied. In order to describe our experimental data, five models were implemented (GAB, Peleg, Chung-Pfost, Oswin, Halsey) and compared. It was found that GAB and Peleg models provide the best fit to the experimental data. On the basis of GAB modeling, the monolayer moisture content for each kind of wood was calculated. Moreover, the hysteresis phenomenon was investigated. The influence of temperature and wood variety on sorption isotherms was also tested.     

Sorption Characteristics of Whole Pistachio Nuts (Pistacia Vera L.)

ABSTRACT

Moisture sorption characteristics of whole pistachio nuts were investigated at 10, 20, and 30°C using the static method. The sorption isotherms exhibited hysteresis over the range of 0.10-0.80 water activity which was succesfully interpreted using BET, GAB, Oswin, Smith, Henderson, Chung-Pfost and Halsey mathematical models and from which the BET, GAB and Oswin models were found to give the best fit. Monolayer moisture content of pistachio nuts was determined from BET and GAB equations and the isosteric heat of sorption data were derived using Clausius-Clapeyron equation and presented in graphical form. The information generated can be utilized to optimize the packaging parameters for long term storage of pistachio nuts.     

WATER SORPTION ISOTHERMS AND GLASS TRANSITION PROPERTIES OF GELATIN

The water sorption isotherms of gelatin of different molecular weights (317,700, 228,900, and 197,400) were determined at 50°C using an isopiestic method. The sorption isotherms were modeled using the Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-deBoer (GAB) equations. The BET and GAB equations were able to predict the equilibrium moisture content (EMC) with a mean relative error of 5.2 and 5.0%, respectively. The BET monolayer moisture content varied from 4.81 to 5.70% (d.b.) while modeling with the GAB equation predicted monolayer moisture content of 6.14-7.58% (d.b.) depending upon molecular weight. The monolayer moisture content increased with increasing molecular weight. Studies on the effect of moisture content on the “rheological glass transition temperature” (T_g) showed a smooth increase in the value of T_g as a function of increasing concentration of gelatin solids. This varied from 7 to 35°C at 75% and 97% solids, respectively for the protein sample with MW = 317,700. Pinpointing of the T_g was implemented with the technique of small deformation dynamic oscillation. It was proposed that the “rheological” T_g is the point between the glass transition region and the glassy state. It acquires physical significance by identifying the transition from free volume phenomena of the polymeric backbone in the glass transition region to an energetic barrier to motions in the glassy state involving stretching and bending of chemical bonds.     

ADSORPTION ISOTHERMS OF RAW AND ROASTED HAZELNUTS

Adsorption isotherms of raw and roasted (at 100°C, 120°C, 140°C and 160°C) hazelnuts of Tombul variety were determined at 25°C, and over relative humidities ranging from 11 to 90% using the gravimetric static method. Eleven sorption models (GAB, BET, Modified BET, Halsey, Iglesias-Chirife, Oswin, Chung-Pfost, Smith, Kuhn, Harkins-Jura and Caurie) were evaluated by using the linear regression method. GAB (Guggenheim-Anderson-de Boer) model satisfactorily described adsorption characteristics of the samples over the experimental range of study. Monolayer values at 25°C were estimated from the GAB model as 0.0155 kg water/kg dry solid for raw and 0.0100–0.0163 kg water/kg dry solid for roasted hazelnuts. Caurie security moisture content for raw hazelnuts was also determined from Caurie model as 0.048 kg water/kg dry solid.