Water desorption isotherms and net isosteric heat of desorption on lignite

<p>Water desorption isotherms of fermented cocoa beans from Ivory Coast were determined using the gravimetric static method of saturated salts solutions at 30 °C, 40 °C and 60 °C, and isosteric heats of desorption were calculated from Clausius-Clapeyron equation. The experimental data were fitted to several isotherm equations. The best fittings were obtained for the BET equation for aw<0.50 (with an average mean relative deviation (MRD) value of 1.56%) and for the Harkins-Jura equation for aw?0.50 (with an average value MRD equation of 4.17%). The isotherms obtained at 30 °C and 40 °C are practically coincident and overlapped for aw below 0.40. Fermented cocoa beans presented a monolayer moisture content of 0.083 dry basis (d.b.) at 30 °C and this value decreases with increasing temperature. The net isostheric heats of desorption for fermented cocoa beans for the temperature range studied (30-60 °C) were estimated as a function of moisture content. The maximum net isosteric heat of desorption for fermented cocoa beans was estimated at around 13.51 kJ/mol corresponding to a moisture content value of 2.85%. The energy requirement for maintaining the moisture content low of 8.7% (d.b.) or 8% wet basis (w.b.) for safe storage of this product or for reducing the moisture content during drying was estimated at around 9.58 kJ/mol.</p>

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Hygroscopicity of baru (Dipteryx alata Vogel) fruit

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v21n4p279-284 ◽

2017 ◽

Vol 21 (4) ◽

pp. 279-284 ◽

Cited By ~ 2

Author(s):

Daniel E. C. de Oliveira ◽

Osvaldo Resende ◽

Lílian M. Costa ◽

Weder N. Ferreira Júnior ◽

Silva Igor O. F.

Keyword(s):

Moisture Content ◽

Water Content ◽

Equilibrium Moisture Content ◽

Gravimetric Method ◽

Isosteric Heat ◽

Water Desorption ◽

Safe Storage ◽

Moisture Contents ◽

Desorption Isotherms ◽

Dipteryx Alata

ABSTRACT With the knowledge on the hygroscopic equilibrium of the baru (Dipteryx alata Vogel) fruit, the product can be adequately handled to maintain the moisture content at the levels recommended for safe storage. Thus, this paper aimed to determine the water desorption isotherms of baru fruits at temperatures of 20, 25, 30 and 35 °C, and water activity between 0.14 and 0.80, and obtain the values of isosteric heat of desorption as a function of the equilibrium moisture content of the product. The equilibrium moisture content was obtained using the static-gravimetric method. Modified Halsey was the best model recommended to represent the hygroscopicity of baru fruits. The recommended moisture contents for safe storage of baru fruits are not more than 19.9, 19.3, 18.6 and 18.0 (%, d.b.) for the respective temperatures of 20, 25, 30 and 35 °C. The integral isosteric heat of desorption increases as the water content decreases, leading to an increment in the energy required to remove water from the product.

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Thermodynamic properties and water desorption isotherms of Golden Delicious apples

Heat and Mass Transfer ◽

10.1007/s00231-018-2527-8 ◽

2018 ◽

Vol 55 (5) ◽

pp. 1405-1418 ◽

Cited By ~ 5

Author(s):

Rym Mbarek ◽

Daoued Mihoubi

Keyword(s):

Thermodynamic Properties ◽

Water Desorption ◽

Golden Delicious ◽

Desorption Isotherms

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Drying Kinetics, Desorption Isotherms and Apparent Diffusivity of Sage Leaves

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.406.173 ◽

2021 ◽

Vol 406 ◽

pp. 173-181

Author(s):

Bensebia Ouahida

Keyword(s):

Effective Diffusivity ◽

Isosteric Heat ◽

Moisture Diffusivity ◽

Storage Conditions ◽

Drying Kinetics ◽

Effect Of Temperature ◽

Medicinal And Aromatic Plants ◽

Oven Drying ◽

Kinetics Modelling ◽

Desorption Isotherms

The use of fresh herb is limited in the food and pharmaceutical industry thats why the dry form of the herb is the one commonly used. To save the quality of medicinal and aromatic plants it is very important to provide optimum drying and storage conditions. The aim of this study is to determine and model the drying kinetics of sage leaves. Initially the desorption isotherms are determined for different temperatures (30, 45 and 60°C). The drying experiments were carried out in a convection oven at the same temperature range. For the desorption isotherms and the drying kinetics various models reported in the literature were used and from the statistical view, the Yanniotis and Blahovec and the Fick models fit well the results of desorption isotherms and the oven drying, respectively. The net isosteric heat of desorption of the sage leaves ranged from 6.86 to 63.45 kJ/mol. The total time of oven drying reduced substantially with an increase of the drying temperature. Effective moisture diffusivity values ranged from 1.1x10-12 to 3.7x10-12 m2/s and significantly affected by temperature. An Arrhenius relation with an activation energy value of 66.87 kJ/mol expressed effect of temperature on the diffusivity. Keywords: Desorption isotherms, Drying kinetics, Modelling, Effective diffusivity, Sage leaves

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Isotherms and isostatic heat of foam-mat dried yellow mombin pulp

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v22n6p436-441 ◽

2018 ◽

Vol 22 (6) ◽

pp. 436-441

Author(s):

Maisa D. Cavalcante ◽

Geovana R. Plácido ◽

Daniel E. C. de Oliveira ◽

Bheatriz S. M. de Freitas ◽

Caroline Cagnin ◽

...

Keyword(s):

Water Content ◽

Water Activity ◽

Nutritional Value ◽

Isosteric Heat ◽

Agricultural Products ◽

Equilibrium Water Content ◽

Desorption Isotherms ◽

Forced Air ◽

Semi Solid ◽

Content Range

ABSTRACT Yellow mombin has high nutritional value but is very perishable. Foam mat drying is a method that has been widely used to preserve liquid and semi-solid powdered foods. In this context, the aim of this study was to determine desorption isotherms and isosteric heat of yellow mombin (Spondias mombin L.) foam for different conditions of temperature and water activity. Powdered yellow mombin pulp was obtained by drying in forced-air oven regulated to 60 ° C. The indirect static method was used to determine the isotherms and isosteric heat, whereas water activity (aw) was determined using the Hygropalm-HP23AW-A analyzer. A B.O.D. incubator, set at 10, 20, 30 and 40 °C, was used to control the temperature, and the water activity for each temperature was between 0.220 and 0.832. The experimental data were fitted to mathematical models frequently used to represent the hygroscopicity of agricultural products, and the best model was the Modified Halsey. Integral isosteric heat of desorption of yellow mombin powder, within the water content range of 17.22 to 57.58 (% d.b.), ranged from 3198.56 to 2598.38 kJ kg-1. It was concluded that the equilibrium water content of yellow mombin pulp powder increased with the increment in water activity; desorption isotherms obtained for yellow mombin pulp powder showed sigmoid form and, with the reduction of water content, the isosteric heat increases.

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