scholarly journals The Thermodynamics of Tobacco-Water Interactions

1999 ◽  
Vol 18 (5) ◽  
pp. 189-204
Author(s):  
JL Banyasz
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Binding Sites ◽  
Water Sorption ◽  
Water System ◽  
Free Water ◽  
Water Binding ◽  
Sorption Data ◽  
General Role ◽  
Water Sorption Isotherm

AbstractAn equation to describe the water sorption isotherm of tobacco is developed based on a model of the tobacco-water system as a mixture or solid solution comprised of water and water binding sites of many different kinds. It is assumed that free water has an activity coefficient of one. The result is an equation that predicts moisture content as a function of relative humidity given the numbers of each of the different kinds of sites and the associated water binding equilibrium constants. It is shown that this multi-site equation reduces to a one site equation if the different kinds of water binding sites are symmetrically distributed with regard to their affinity for water. The result is a two parameter, average site equation that fits water sorption data for tobacco over the range of 10-80% relative humidity. The average site equation is identical to the equation derived by BRUNAUER, EMMETT and TELLER for binding to surface sites (1). The two models start from very different points of view but come to the same conclusion because they are ultimately based on thermodynamics which is indifferent as to the physical nature of the sites. Inferences as to the microscopic nature of water binding sites cannot be made from thermodynamic isotherm equations. In order to describe the effects of water on the physical properties of tobacco the solution analogy is extended further. If tobacco is a mixture or solution of unhydrated sites, hydrated sites and free water, then the value of a physical property should be a function of the concentrations of those species and the associated partial molar values of the property. As the total moisture content changes the distribution of species will change and, in turn, change the properties. Applications of this rationale are presented for heat capacity, thermal diffusivity and the kinetics of the Browning reaction. The results demonstrate that the parameters derived from water sorption data play a more general role in the thermodynamics of the tobacco-water system.

scholarly journals Determination of Moisture Sorption Isotherm of Crosslinked Millet Flour and Oxirane Using GAB and BET

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
M. S. Alamri ◽  
A. A. Mohamed ◽  
S. Hussain ◽  
M. A. Ibraheem ◽  
Akram A. Abdo Qasem
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Sorption Isotherm ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Water Binding ◽  
Moisture Sorption Isotherm ◽  
Water Sorption Isotherm ◽  
Moisture Sorption Isotherms ◽  
Different Temperatures

Epoxy resin was prepared by crosslinking epoxidized oil and millet flour. The reaction was carried out at three different temperatures (25, 40, and 55°C) and zinc chloride levels (1, 2, and 3%). Moisture sorption isotherms were determined at 0.1 to 0.9 water activity (aw) using a gravimetric sorption analyzer (Q 2000). The sigmoidal shape (type II) of the resin isotherms exhibited lower equilibrium moisture content (EMC) at higher temperature. The experimental data were modeled using GAB (Guggenheim–Anderson–de Boer) and BET (Brunauer–Emmett–Teller). The EMC of the resin was significantly lower than that of the flour, which could be attributed to the decrease in the number of water-binding sites due to the creation of dense areas during crosslinking. The low root-mean-square error (RMSE) indicates that GAB and BET were suitable for predicting the water sorption isotherm for millet flour resin. The heat of sorption of the resin was large at low moisture content and increased at higher relative humidity. It is recommended that millet flour resin be used at relative humidity below 60%.

scholarly journals Drying kinetics and determination of water sorption isotherms of corn

2017 ◽  
Vol 15 (2) ◽  
Author(s):  
J Roy ◽  
MA Alim ◽  
MN Islam
Keyword(s):  
Moisture Content ◽  
Sorption Isotherm ◽  
Water Sorption ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Drying Kinetics ◽  
Drying Time ◽  
Moisture Sorption Isotherm ◽  
Water Sorption Isotherm ◽  
Monolayer Moisture

The study was carried out for the purpose of determining the drying kinetics as well as moisture sorption isotherm of hybrid-81 corn. Corn at about 31% moisture content (wb) was dried in a forced convective hot air cabinet dryer at different drying conditions, such as variable air dry bulb temperature (40°C, 50°C and 60°C) and loading density (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2) as well as in shining sun at different layers (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2). The water sorption isotherm of the dried corn was developed using vacuum desiccators, which contained saturated salt solutions in the range of 11-93% RHs. The mono-layer moisture content calculated by the Brunauer–Emmett–Teller (BET) model (6.76 g/100 g solid) was lesser than that calculated by the Guggenheim–Anderson–De Boer (GAB) model (10.53 g/100 g solid). The energy constants were 10.45 and 4.64 as per BET and GAB equation, respectively. Both models gave suitable fits for corn. The activation energy (Ea) for diffusion of water was found to be 11.09 kcal/gm-mole for corn. Furthermore, it was noticed that, with the increase of corn layer, the drying rate decreased in case of both sun and mechanical drying. However, higher loading density resulted in efficient drying, at least up to 10.7 kg/m2. It was shown that the drying time to obtain stability was the lowest for moisture content (12.08 %) corresponding to aw of 0.65 in case of BET or GAB monolayer moisture content. This finding could be helpful in predicting the storage life of corn.J. Bangladesh Agril. Univ. 15(2): 309-317, December 2017

Water sorption in wood and modified wood at high values of relative humidity. Part I: Results for untreated, acetylated, and furfurylated Norway spruce

Holzforschung ◽  
2010 ◽  
Vol 64 (3) ◽  
Author(s):  
Lisbeth G. Thygesen ◽  
Emil Tang Engelund ◽  
Preben Hoffmeyer
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Norway Spruce ◽  
Water Sorption ◽  
Capillary Condensation ◽  
Theoretical Contribution ◽  
Low Field ◽  
Condensed Water ◽  
Relaxation Curves ◽  
Curve Form

Abstract Desorption isotherms at 20°C for untreated, acetylated, and furfurylated Norway spruce [Picea abies (L.) Karst.] sapwood were established in the 91.9–99.9% relative humidity (RH) range. Three methods were employed to secure various constant RH levels: saturated salt solutions, climate chambers, and the pressure plate technique. The curve form for the untreated samples did not show an upward bend, except perhaps above 99.5% RH, indicating that – contrary to what has hitherto been assumed – capillary condensation does not play a significant role for water sorption in wood below fiber saturation. Three additional results corroborate this conclusion: (1) calculation of the theoretical contribution of capillary condensation to the moisture content (MC) in wood based on idealized microstructural geometries by means of the Kelvin and Laplace equations resulted in very small contributions to the equilibrium moisture content (EMC), i.e., below 0.35% moisture at 99.9% RH. (2) The ratio between the EMC of acetylated and untreated samples did not show an increasing trend for increasing RH, as would have been the case if capillary condensation had taken place in both untreated and acetylated wood. (3) Low field time domain nuclear magnetic resonance results showed that only the relaxation curves from the furfurylated samples were affected systematically by freezing, indicating that neither untreated nor acetylated wood contained significant amounts of capillary condensed water.

scholarly journals Study on water sorption isotherm of summer onion

2015 ◽  
Vol 40 (1) ◽  
pp. 35-51 ◽  
Author(s):  
Md Masud Alam ◽  
Md Nazrul Islam
Keyword(s):  
Moisture Content ◽  
Sorption Isotherm ◽  
Water Sorption ◽  
Moisture Sorption ◽  
Moisture Sorption Isotherm ◽  
Water Sorption Isotherm ◽  
Monolayer Moisture Content ◽  
Using Data ◽  
Monolayer Moisture ◽  
Added Salt

The water sorption characteristics of dehydrated onion and onion solutes composite by vacuum drying (VD) and air drying (AD) were developed at room temperature using vacuum desiccators containing saturated salt solutions at various relative humidity levels (11-93%). From moisture sorption isotherm data, the monolayer moisture content was estimated by Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) equation using data up to a water activity of 0.52 and 0.93 respectively. Results showed that in case of non treated samples the monolayer moisture content values (Wo) of BET gave slightly higher values than GAB (9.7 vs 8.2) for VD, while GAB gave higher value than BET (11.0 vs 9.8) for AD. It is also seen that the treated and non treated onion slice and onion powder absorbed approximately the same amount of water at water activities below about 0.44 and above 0.44 the treated samples begin to absorb more water than the non treated samples. It was observed that 10-20% added of sugar gave no change in water sorption capacity while the amount of sorbed water increases with increasing amount added salt for mix onion product.Bangladesh J. Agril. Res. 40(1): 35-51, March 2015

Influence of roasting on the water sorption isotherms of nuts / Influencia del tueste sobre las isotermas de sorción de agua de diferentes frutos secos

1996 ◽  
Vol 2 (6) ◽  
pp. 399-404 ◽  
Author(s):  
N. Martínez-Navarrete ◽  
A. Chiralt
Keyword(s):  
Moisture Content ◽  
Water Sorption ◽  
Sorption Isotherms ◽  
Fat Content ◽  
Water Binding ◽  
Mono Layer ◽  
Thermodynamic Driving Force ◽  
Water Affinity ◽  
Sorption Heat ◽  
Cellular Components

This work studies the influence of the roasting process on sorption isotherms of almond, hazelnut and peanut over the normal range of storage temperatures (5, 25 and 45 °C) The results obtained showed that water sorption properties of unroasted nuts are affected by fat content. The mono layer moisture content and water affinity (sorption heat, Qs) increased when the nut fat content decreased. After roasting, a more homogeneous water affinity was observed for the different products, although fat content still affected the monolayer capacity. Also, roasting reduced mono layer moisture content and Qs values in each sample and made the moisturizing process less spontaneous (decreasing the thermodynamic driving force). These results are consistent with an increase of the hydrophobicity of the cellular components of nuts due to the enhancement of lipid interactions. The water binding properties of active points in the roasted products were reduced and, hence, some water sorption active points disappeared.

Water sorption characteristics of seeds of four Western Australian species

2003 ◽  
Vol 51 (1) ◽  
pp. 85 ◽  
Author(s):  
D. J. Merritt ◽  
D. H. Touchell ◽  
T. Senaratna ◽  
K. W. Dixon ◽  
K. Sivasithamparam
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Water Sorption ◽  
Storage Temperature ◽  
Sorption Isotherms ◽  
Seed Storage ◽  
Water Binding ◽  
Western Australian ◽  
Seed Water Content ◽  
Sorption Characteristics

The relationship between storage temperature, relative humidity and seed water content was investigated for four species native to Western Australia: Acacia bivenosa DC., Anigozanthos manglesii D.Don., Banksia ashbyi E.G.Baker and Mesomelaena tetragona (R.Br.) Benth. Water sorption isotherms were constructed at 5, 23 and 50�C and the enthalpy of water sorption was calculated by van�t Hoff analysis. Seeds of three species, A. manglesii, B.�ashbyi and M. tetragona, showed a sigmoidal relationship between seed water content and relative humidity. Intact seeds of Acacia bivenosa maintained a constant water content at temperatures of 23�C or less due to the impermeable seed coat; however, isotherms of scarified seeds were similar in shape to those of the other species at all temperatures. The enthalpy of water sorption ranged from –19 kJ mol–1 for M. tetragona seeds to –29 kJ mol–1 for B. ashbyi seeds and was dependent on water content. However, all species had a maximum sorption strength at 2–6% water content and three regions of water-binding strength were evident. Each of these species has water sorption characteristics consistent with orthodox storage behaviour and the results of this study provide a framework for improving seed storage methods for the highly diverse Western Australian flora.

scholarly journals Water Sorption and Mechanical Properties of Starch/Chitosan Nanoparticle Films

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Siti H. Othman ◽  
Nurul R. A. Kechik ◽  
Ruzanna A. Shapi’i ◽  
Rosnita A. Talib ◽  
Intan S. M. A. Tawakkal
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Water Sorption ◽  
Food Packaging ◽  
High Water ◽  
Storage Conditions ◽  
Sorption Behavior ◽  
Sorption Data ◽  
Chitosan Nanoparticle ◽  
The Stability

The usage of biopolymer as food packaging material has been limited due to high water sorption and poor mechanical properties of the biopolymer. Thus, this study is aimed at improving the water sorption and mechanical properties of biopolymer particularly starch films by incorporation of a natural filler particularly chitosan nanoparticle (CNP) and investigating the properties of starch/CNP films at different storage conditions (relative humidity: 23, 50, and 75%; temperature: 4, 30, and 40°C). The water sorption behavior and isotherms of the films were investigated by fitting the water sorption data to the Peleg model and Guggenheim, Anderson, and de Boer model. Both the models were well fitted to the experimental data, thus proving the reliability of water sorption behavior prediction. It was found that different storage conditions of the films significantly affected the mechanical properties of the films due to the sensitivity of the films towards moisture. Water sorption and mechanical properties of the films were best improved at relative humidity of 23% and temperature of 30°C. The water sorption and mechanical properties of the films are worth to be investigated because the properties affected the stability, shelf life, and application of the films in the food packaging field.

Moisture sorption isotherm of cross-linked wheat gluten and epoxydized oil using GAB and BET

2019 ◽  
Vol 27 (9) ◽  
pp. 536-545
Author(s):  
AA Mohamed ◽  
MS Alamri ◽  
S Hussain ◽  
MA Ibraheem ◽  
Akram A Abdo Qasem
Keyword(s):  
Moisture Content ◽  
Free Volume ◽  
Sorption Isotherm ◽  
Wheat Gluten ◽  
Moisture Sorption ◽  
Cross Linking ◽  
Water Binding ◽  
Clapeyron Equation ◽  
Moisture Sorption Isotherm ◽  
Water Sorption Isotherm

The moisture sorption isotherm of wheat gluten/epoxydized sesame or sunflower oil resin was determined at 25, 40, and 55°C. The resin was prepared by cross-linking epoxydized oil and wheat gluten using 1, 2, and 3% zinc chloride as the catalyst. The experiment was carried out over 0.1–0.9 water activity ( a w) range using gravimetric sorption analyzer (Q 2000, TA Instruments, New Castle, PA, USA). The resin isotherms were found to be type III shape where the equilibrium moisture content (EMC) was higher at lower temperatures. The EMC of gluten epoxy resin was dependent on the degree of cross-linking because more cross-linking decreased EMC. The Guggenheim Anderson-de Boer (GAB) parameters support the theory of the free volume as it relates to monolayer absorption. This could be attributed to the decrease in the number of water binding sites due to the development of dense areas during cross-linking and increase in the free volume. The GAB and Brunauer–Emmett–Teller were found to be suitable for predicting the water sorption isotherm for gluten protein resin because it provided low root mean square error. The heat of sorption based on the Clausius–Clapeyron equation (qst) increased with decrease in moisture content.

Correlation of modified water sorption properties with the decline of storage stability of osmotically-primed seeds of Vigna radiata (L.) Wilczek

1997 ◽  
Vol 7 (4) ◽  
pp. 391-398 ◽  
Author(s):  
Wendell Q. Sun ◽  
Dora C. Y. Koh ◽  
Choong-Moi Ong
Keyword(s):  
Binding Sites ◽  
Vigna Radiata ◽  
Water Sorption ◽  
Mung Bean ◽  
Storage Stability ◽  
Sorption Properties ◽  
Water Binding ◽  
Water Redistribution ◽  
Water Sorption Properties ◽  
Glycol Solution

AbstractOsmotic priming in a polyethylene glycol solution (300 g/kg water) for 48 h resulted in a partial loss of desiccation tolerance for seeds of Vigna radiata (L.) Wilczek (mung bean). The percentage of germination began to decrease after primed seeds were dried down to water contents less than 0.06 g/g DW. As compared with control seeds, primed mung bean seeds also had poorer storage stability. The decline of storage stability after osmotic priming was correlated with the modifications of seed water sorption properties. Priming significantly increased the amount of water associated with the weak water-binding sites, and reduced the amount of water associated with the strong binding sites and multi-molecular binding sites in seed tissues. The enhancement of molecular mobility in seeds, as a result of such water redistribution, probably accelerates seed deterioration and decreases storage stability.

CATFISH DRYING (Clarias Batraclus) USING ‘TEKO BERSAYAP’ SOLAR DRYER

2012 ◽  
Vol 2 (1) ◽  
pp. 14-20
Author(s):  
Yuwana Yuwana
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Ambient Temperature ◽  
Drying Rate ◽  
Drying Process ◽  
Drying Time ◽  
Ambient Relative Humidity ◽  
Solar Dryer

Experiment on catfish drying employing ‘Teko Bersayap’ solar dryer was conducted. The result of the experiment indicated that the dryer was able to increase ambient temperature up to 44% and decrease ambient relative humidity up to 103%. Fish drying process followed equations : KAu = 74,94 e-0,03t for unsplitted fish and KAb = 79,25 e-0,09t for splitted fish, where KAu = moisture content of unsplitted fish (%), KAb = moisture content of splitted fish (%), t = drying time. Drying of unsplitted fish finished in 43.995 hours while drying of split fish completed in 15.29 hours. Splitting the fish increased 2,877 times drying rate.

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