scholarly journals Kinetics of water sorption of damaged bean grains: Thermodynamic properties

2017 ◽  
Vol 21 (8) ◽  
pp. 556-561 ◽  
Author(s):  
Paulo C. Corrêa ◽  
Fernanda M. Baptestini ◽  
Jaime D. B. Vanegas ◽  
Rafael Leite ◽  
Fernando M. Botelho ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Moisture Content ◽  
Adsorption Process ◽  
Initial Moisture Content ◽  
Mechanical Damage ◽  
Climatic Chamber ◽  
Desorption Process ◽  
Adsorption Sites ◽  
Differential Enthalpy ◽  
Kinetics Of

ABSTRACT This study aims to determine the thermodynamic properties of damaged beans. Grains with initial moisture content of 53.85% (d.b.) were used. A part of the grains was used to obtain the desorption isotherms, while another part was subjected to drying until a moisture content of 5.26% (d.b.) was achieved; therefore, it was subjected to the adsorption process. To induce damage, a Stein breakage tester was used. To obtain the equilibrium moisture content, grains were placed in a climatic chamber whose temperatures were 20, 30, 40, and 50 ± 1 °C combined with a relative humidity of 30, 40, 50, 70, and 90 ± 3%. Although in the desorption process, damaged grains had a lower differential enthalpy compared with the control, the reverse behavior was observed in the adsorption process. Mechanical damage caused the formation of a greater number of available adsorption sites, resulting in higher differential entropy values in adsorption and lower values in desorption compared with the control. The mechanical damage had no effect on the Gibbs free energy.

scholarly journals Water sorption kinetics of damaged beans: GAB model

2017 ◽  
Vol 21 (8) ◽  
pp. 550-555 ◽  
Author(s):  
Fernanda M. Baptestini ◽  
Paulo C. Corrêa ◽  
Jaime D. B. Vanegas ◽  
Rafael Leite ◽  
Fernando M. Botelho ◽  
...  
Keyword(s):  
Moisture Content ◽  
Water Sorption ◽  
Initial Moisture Content ◽  
Sorption Kinetics ◽  
Climatic Chamber ◽  
Gab Model ◽  
Monolayer Moisture ◽  
Increasing Temperature ◽  
And Control ◽  
Kinetics Of

ABSTRACT The objective of this study was to model the water sorption kinetics of damaged beans. Grains with initial moisture content of 53.85%, dry basis (d.b.), were used. One portion of the grains was used to obtain desorption isotherms, while the other was subjected to drying until the moisture content of 5.26% (d.b.), so that it was subjected to the adsorption. For the induction of damage, a Stein Breakage Tester was used. To obtain the equilibrium moisture content, grains were placed in a climatic chamber at 20, 30, 40 and 50 ± 1 °C combined with relative humidity of 30, 40, 50, 70 and 90 ± 3%. The GAB model fitted well to the equilibrium moisture experimental data of damaged grains and control. With increasing temperature, the monolayer moisture contents decreased in adsorption and desorption processes, ranging from 9.84 to 5.10% d.b. The lower moisture content in the monolayer in damaged grains indicates that lower moisture content is necessary to ensure their conservation.

scholarly journals Thermodynamic properties of water desorption in lettuce seeds

2018 ◽  
Vol 39 (3) ◽  
pp. 921
Author(s):  
Juliana Soares Zeymer ◽  
Paulo Cesar Corrêa ◽  
Gabriel Henrique Horta de Oliveira ◽  
Fernanda Machado Baptestini
Keyword(s):  
Thermodynamic Properties ◽  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Initial Moisture Content ◽  
Gravimetric Method ◽  
Chemical Components ◽  
Water Molecules ◽  
Water Desorption ◽  
Desorption Process ◽  
Lettuce Seeds

Knowledge of the movement of water molecules inside material is important for the study of interactions between water and chemical components of agricultural products. The thermodynamic properties calculation reports this need, being the source of information to design drying equipment, calculate the energy required in this process and evaluate the physical phenomena that occur on the food surface. Given the importance of the subject, the objective of this study was to determine the thermodynamic properties of the water desorption process in lettuce seeds. Lettuce seeds had an initial moisture content of 9.3% (d.b.). The equilibrium moisture content of seeds was determined by static gravimetric method at different temperatures (10, 20, 30, 40 and 50 ± 1 °C) and relative humidity values (between 11 and 96%). Experiments were conducted in triplicate. It was observed that, with increasing equilibrium moisture content, there was a reduction in the energy required for evaporation of water in lettuce seeds, with values of integral isosteric heat of desorption in the water content range 2.1 to 21.2% (d.b.) which varied from ‘4164.89 to 2477.43’ kJ kg-1. With increasing equilibrium moisture content there was a decrease in differential entropy, resulting in lower demand for mobility of water molecules. The Gibbs free energy also decreased with increasing equilibrium moisture content and was positive for all temperatures studied, showing non-spontaneity of water desorption in the seeds. The enthalpy-entropy compensation theory was has been satisfactorily applied to the sorption phenomenon and the water desorption process in lettuce seeds was controlled by enthalpy.

scholarly journals Thermodynamic properties of Anacardium humile St. Hil. (cajuzinho-do-cerrado) achenes

2018 ◽  
Vol 39 (6) ◽  
pp. 2351
Author(s):  
Karine Feliciano Barbosa ◽  
Juliana De Fátima Sales ◽  
Osvaldo Resende ◽  
Daniel Emanuel Cabral de Oliveira ◽  
Ana Lúcia Cabral ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Moisture Content ◽  
Native Species ◽  
Equilibrium Points ◽  
Isokinetic Temperature ◽  
Desorption Process ◽  
Moisture Contents ◽  
Differential Enthalpy ◽  
Enthalpy And Entropy ◽  
Latent Heat Of Vaporization

The cajuzinho-do-cerrado is a native species of the cerrado of great potential of use and is threatened of extinction. The aim of this study was to determine and evaluate the thermodynamic properties of Anacardium humile St. Hil. achenes from the different hygroscopic equilibrium points according to the moisture content. To obtain the isotherms, the indirect static method was used at temperatures of 10, 20, 30 and 40 °C and for moisture contents of 13.4, 11.1, 8.7 and 5.3% dry basis (db). The Copace model was used to describe the hygroscopic equilibrium of the achenes. The thermodynamic properties are influenced by the moisture content because the latent heat of vaporization of the water of the achenes increases with the decrease in the equilibrium moisture content, varying between 3,035.63 and 2,510.80 kJ kg-1 for moisture contents of 4.51 to 13.4% db, respectively. The differential enthalpy and entropy are closely related to the moisture content of the achenes. The isokinetic temperature of 304.67 K denotes the linear chemical compensation between the differential enthalpy and entropy of the Anacardium humile St. Hil. achenes, and the desorption process is controlled by enthalpy.

scholarly journals Moisture desorption isotherms of cucumber seeds: modeling and thermodynamic properties

2015 ◽  
Vol 37 (3) ◽  
pp. 218-225 ◽  
Author(s):  
Paulo Cesar Corrêa ◽  
Maycon Fagundes Teixeira Reis ◽  
Gabriel Henrique Horta de Oliveira ◽  
Ana Paula Lelis Rodrigues de Oliveira ◽  
Fernando Mendes Botelho
Keyword(s):  
Free Energy ◽  
Relative Humidity ◽  
Thermodynamic Properties ◽  
Moisture Content ◽  
Gibbs Free Energy ◽  
Content Increase ◽  
Statistical Parameters ◽  
Thermodynamic Relation ◽  
Differential Enthalpy ◽  
Desorption Isotherms

Hygroscopic equilibrium curves or sorption isotherms are important in order to define dehydration limits of the product, estimate moisture content alterations under environment conditions and to acquire moisture content values for safe storage. This work aimed to determine desorption isotherms of cucumber seeds stored at different temperature (10, 20, 30, 40 and 50 ºC) and relative humidity (0.11 to 0.96) and the thermodynamic properties of this process. Mathematical models were fitted to experimental data in order to represent the agricultural products hygroscopicity. Net isosteric heat of desorption was performed based on the Clausius-Clapeyron thermodynamic relation and Gibbs free energy through the Van't Hoff equation. Based on statistical parameters, Modified Henderson model was the one that best represented hygroscopicity of cucumber seeds. Equilibrium moisture content of cucumber seeds decreased with temperature increment at a constant value of relative humidity. Differential enthalpy values, representing the energy required to remove moisture from the cucumber seeds, ranged from 2923 to 2469 kJ. kg-1. Values of differential entropy and Gibbs free energy decreased with moisture content increase. Enthalpy-entropy compensation theory is valid for the sorption of cucumber seeds, in which the water sorption mechanism in cucumber seeds can be considered to be enthalpy controlled.

scholarly journals Moisture Adsorption and Thermodynamic Properties of California Grown Almonds (Varieties: Nonpareil and Monterey)

2012 ◽  
Vol 1 (1) ◽  
Author(s):  
Li Zuo Taitano ◽  
R.P. Singh
Keyword(s):  
Diffusion Coefficient ◽  
Thermodynamic Properties ◽  
Moisture Content ◽  
Water Activity ◽  
Gravimetric Method ◽  
Isosteric Heat ◽  
Moisture Adsorption ◽  
Constant Weight ◽  
Differential Enthalpy ◽  
Monolayer Moisture

Moisture adsorption characteristics of California grown almonds (Nonpareil: pasteurized and unpasteurized almonds; Monterey: pasteurized, unpasteurized and blanched almonds) were obtained using the gravimetric method over a range of water activities from 0.11 to 0.98 at 7-50ºC. The weights of almonds were measured until samples reached a constant weight. The relationship between equilibrium moisture content and water activity was established using the Guggenheim-Anderson-de Boer model. The diffusion coefficient of water in almond kernels was calculated based on Ficks second law. The monolayer moisture value of almonds ranged from 0.020 to 0.035 kg H2O kg-1 solids. The diffusion coefficient increased with temperature at a constant water activity, and decreased with water activity at a constant temperature. The thermodynamic properties (net isosteric heat, differential enthalpy and entropy) were also determined. The net isosteric heat of adsorption decreased with the increasing moisture content, and the plot of differential enthalpy versus entropy satisfied the enthalpy-entropy compensation theory. The adsorption process of almond samples was enthalpy driven over the range of studied moisture contents.

scholarly journals Modelado matemático de secado solar de orégano (Plectranthus amboinicus) con tecnologías directas e indirectas

2020 ◽  
pp. 27-36
Author(s):  
Beatriz Castillo-Téllez ◽  
Margarita Castillo-Téllez ◽  
Erick César López-Vidaña ◽  
Gerardo Alberto Mejía-Pérez
Keyword(s):  
Moisture Content ◽  
Temperature Effects ◽  
Initial Moisture Content ◽  
Operating Conditions ◽  
Solar Drying ◽  
Drying Behavior ◽  
Medicinal Properties ◽  
Plectranthus Amboinicus ◽  
Time Required ◽  
Kinetics Of

Oregano is a plant with many nutritional and medicinal properties; there are also other applications in the chemical industry. In this work, the drying kinetics of oregano leaves are studied using a cabinet-type dryer with and without a forced convention, open sun drying, and indirect solar drying. The samples had an initial moisture content of 80 % and the final content of 9 %. The results indicate that indirect solar drying provides better control of operating conditions and greater protection against temperature effects, producing better quality in the dry product. The time required to reach the equilibrium moisture content in all experiments ranged from 375 to 600 min. The data were also adjusted to various mathematical models, resulting In Weibull, Logarithmic, and Page, which best represent the drying behavior of oregano leaves. The statistics used for indirect solar dryer are R2 of 0.9969, 0.9968, and 0.9945, X2 of 0.0363, 0.0363 and 0.0599 respectively.

Diffusion of Water in Chestnut Fruits during Drying and Rehydration Processes at Different Temperatures

2008 ◽  
Vol 273-276 ◽  
pp. 758-763
Author(s):  
Ramón Moreira ◽  
Francisco Chenlo ◽  
L. Chaguri ◽  
Christiana Fernandes
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Convective Drying ◽  
Transfer Processes ◽  
Hot Air ◽  
Mass Transfer Processes ◽  
Different Temperatures ◽  
Diffusional Model ◽  
Kinetics Of

Many food materials must be dried in order to decrease its water activity and to increase the shelf-life. Also, rehydration operation must be carried out as previous step before consumption. Both operations are commonly employed in some industrial chestnut processing. These processes can be carried out at different temperatures and in all cases the quality of the final product can be affected. In this work, convective drying with hot air is the employed method for water removal and rehydration is carried out by immersion of chestnut in water. In both cases, mass transfer processes are governed by water diffusion in the bulk of the solid. The aim of this work is to determine experimentally the drying and rehydration kinetics of chestnut samples at different conditions of temperature and moisture content. Obtained data are modeled with a diffusional model taking into account volume variations and the corresponding values of the coefficients of diffusion of water are obtained. Analysis of the results indicates that drying/rehydration rates increase with temperature and rehydration kinetics are also depending on the initial moisture content of chestnut. Finally, leaching flow during rehydration is only important at high temperature due to starch gelatinization processes.

Kinetics of forced convective air drying of potato and squash slabs / Cinética del secado de rodajas de patatas y calabacin con corriente de aire

1997 ◽  
Vol 3 (4) ◽  
pp. 251-261 ◽  
Author(s):  
C.O. Rovedo ◽  
C. Suárez ◽  
P.E. Viollaz
Keyword(s):  
Moisture Content ◽  
Surface Area ◽  
Initial Moisture Content ◽  
Three Dimensional ◽  
Sorp Tion ◽  
Air Drying ◽  
Solid Diffusion ◽  
Drying Behaviour ◽  
Drying Curves ◽  
Kinetics Of

Moisture content, temperature, and surface area variations of potato and squash slabs were measured during forced convective air drying; the effect of the initial moisture content on drying behaviour was also investigated. A mathematical model that numerically integrated the diffusion equation and the thermal balance for a three-dimensional shrinking slab was used to simulate the drying process. The parameters of the model (surface area, heat transfer coefficient and dry solid density) were experimentally determined. Fitting parameters (activation energy and pre- exponential coefficient in the Arrhenius equation) were found by comparing experimental and predicted drying curves. Good agreement was obtained down to a moisture level of 0.4 kg water/kg dry solid. Diffusion coefficients were independent of their moisture content within the range studied for both products. The activation energies for potato and squash were 2.09 x 104 kJ/kg mol and 3.76 x 10 4 kJ/kg mol, respectively. Changes in the rates of drying and heating curves for potato took place at moisture levels around 0.4 kg water/kg dry solid, but this was not the case for squash. The differences were mainly attributed to the different shapes of the sorp tion isotherms.

Isotherm Adsorption Behavior and Drying Kinetics of Black Pepper

2012 ◽  
Vol 622-623 ◽  
pp. 1580-1585
Author(s):  
A. Sae-Khow ◽  
S. Tirawanichakul ◽  
Y. Tirawanichakul
Keyword(s):  
Energy Consumption ◽  
Relative Humidity ◽  
Moisture Content ◽  
Specific Energy ◽  
Specific Energy Consumption ◽  
Initial Moisture Content ◽  
Black Pepper ◽  
Drying Kinetics ◽  
Drying Temperature ◽  
Kinetics Of

The objective of this research were to evaulate equilibrium moisture contents (EMC) of black pepper using the gravimetric-static method and to study the drying kinetics of pepper using 1-stage hot air (HA) drying, 1-stage infrared (IR) drying, 2-stages drying with microwave (MW) and IR and 2-stages drying with MW and HA including to the specific energy consumption determination. For the first objective, the five saturated salt solutions were used for providing equlibrate state between pepper and surrounding at temperature ranging of 40-65°C correlated to relative humidity ranging of 10-90%. The results showed that EMC value decreased with increasing temperature at constant relative humidity. To evaluate the EMC value, the experimental data was simulated by four conventional EMC models and the criteria of the best fiiting models were determined by the determination of coefficient (R2) and the root mean square error (RMSE) value. The results showed that the calculated value using the Modified Oswin model was the most suitable for describing the relationship among equilibrium moisture content, relative humidity and temperature. To study effect of drying condition on drying kinetics, the initial moisture content and final moisture content after drying of papper sample was in ranges of 300-400% dry-basis and 12-16% dry-basis, respectively. The experimetal data were simulsted using empirical drying models and the results showed that the drying temperature relatively affected to drying rate of pepper while the evolution of moisture transfer was in the drying falling ratefor all drying strategies. The 1-stage IR drying and 2-stages drying with MW and IR provided low specific energy consumption (SEC) (0.11-0.15 MJ/kg of water evaporated) compared to the other drying strategies (0.87-1.52 MJ/kg of water evaporated). Moreover, the SEC of pepper drying decreased with increasing of drying temperature.

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