scholarly journals The effect of temperature on the okra drying process: kinetic study and physical properties of powders

2021 ◽  
pp. 649-660
Author(s):  
Francislaine Suelia dos Santos ◽  
Rossana Maria Feitosa de Figueirêdo ◽  
Alexandre José de Melo Queiroz ◽  
Ana Raquel Carmo de Lima ◽  
Thalis Leandro Bezerra de Lima
Keyword(s):  
Free Energy ◽  
Physical Properties ◽  
Gibbs Free Energy ◽  
Effective Diffusion ◽  
Effective Diffusivity ◽  
Effect Of Temperature ◽  
Drying Temperature ◽  
Drying Kinetic ◽  
Drying Models ◽  
The One

This study aimed to evaluate the effect of drying temperature (50, 60, 70 and 80 °C) on okra dehydration by comparing its powder’s physical properties obtained from a sample produced by a lyophilization process. Ten drying models were adjusted to the experimental data of the drying kinetics. As a result, effective diffusivity and activation energy were determined in addition to thermodynamic parameters: entropy, enthalpy and Gibbs free energy. A physical characterization, as well as the pigments and colorimetry analyses of the aforementioned powders were made, by comparing them with samples produced by lyophilization. The powders were characterized for hygroscopicity, solubility, wettability, apparent and compacted density, fluidity and cohesiveness, pigments, colorimetric, morphological analysis (SEM) and X-ray diffraction. Midilli model was the one that best adjusted to the drying kinetic curves. There was a booster in the effective diffusion coefficient with the increase of temperature. Enthalpy and entropy were reduced with the increase of both drying temperature and Gibbs free energy. The powders presented high luminosity, and the lyophilized powder had higher pigments retention and greater solubility. All powders presented poor fluidity and intermediate cohesiveness, with amorphous, irregular and asymmetric particles. Thus, from the present study it was possible to evaluate the best drying method, the one that should be applied for the drying of okra, considering the costs involved, its quality and the final application of the product, meeting the specific needs of each consumer

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

Design and Thermodynamic Analysis on One-Step Amination of Benzene to Aniline Systems

2012 ◽  
Vol 550-553 ◽  
pp. 2607-2611
Author(s):  
Chun Hua Yang ◽  
Gang Chen ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Driving Force ◽  
Theoretical Basis ◽  
Free Energies ◽  
One Step ◽  
The One ◽  
Further Development

Seven systems of one-step synthesis of aniline were designed, and it was determined which one could occur spontaneously through the calculation of Gibbs free energy of it. Among the seven systems, the Gibbs free energy of the one with ammonia as the aminating agent and hydrogen peroxide as the oxidant was the lowest, thus its process driving force was the largest, that is, .For this system just mentioned above, the standard Gibbs free energies, the equilibrium constant and the equilibrium conversions of benzene under different conditions were discussed ,which was expected to provide a theoretical basis for further development and application of the system.

Thermodynamics of the Dimensional Changes in the Wheat Kernel during Cooking for Bulgur Production

2004 ◽  
Vol 10 (4) ◽  
pp. 243-253 ◽  
Author(s):  
M. Bayram ◽  
M. D. öner ◽  
S. Eren
Keyword(s):  
Free Energy ◽  
Physical Properties ◽  
Gibbs Free Energy ◽  
Rate Constant ◽  
Rate Of Change ◽  
Lower Amount ◽  
Dimensional Changes ◽  
Wheat Kernel ◽  
Cooking Temperature ◽  
Positive Rate

Thermodynamics and physical properties of the dimensional changes in the wheat kernel during cooking was carried out for bulgur production at 87, 92 and 97°C for 140min. There were determined changes of the length ( x-dimension), two widths ( y- and z-dimensions), weight, volume and density of the wheat kernel. The length of the wheat kernel during cooking decreased, although crease-side width ( y-dimension) and secondary width ( z-dimension) significantly increased ( p 0.05) at each cooking temperature between 6.95-68.05% and 9.95-69.00%, respectively. The volume of the kernel during cooking also significantly ( p 0.05) increased (27.35-185.20%), and had a greater percentage change value than the weight (19.25-160.70%) due to swelling of the wheat kernel. Therefore, density decreased negatively. Activation energy, enthalpy, entropy and Gibbs free energy were used to describe the changes of physical attributes of the wheat kernel during cooking. Rate constant values for the length and density of the wheat kernel were negative in contrast to positive rate constant values of the widths, weight and volume of the wheat kernel. The influence of cooking temperature on the physical properties of the wheat kernel revealed that the rate of change in the secondary width ( z-dimension), weight and density of the wheat kernel were more sensitive to temperature due to their greater activation energies, 5.95 107, 5.26 107 and 6.11 107 J, respectively. In contrast, the y-dimension of width of the wheat kernel required a lower amount of energy due to crease side. All of the changes in physical properties agreed with the positive values of Gibbs free energy.

DRYING CHARACTERISTICS OF ONION PROCESSING WASTE

2021 ◽  
Vol 14(63) (1) ◽  
pp. 193-200
Author(s):  
Tsvetko PROKOPOV ◽  
Maryia GEORGIEVA ◽  
Milena NIKOLOVA ◽  
Dimitar ATANASOV ◽  
Donka TANEVA
Keyword(s):  
Effective Diffusivity ◽  
Total Flavonoid ◽  
Total Phenolic ◽  
Total Flavonoid Content ◽  
Processing Waste ◽  
Flavonoid Content ◽  
Drying Characteristics ◽  
Drying Temperature ◽  
Drying Kinetic ◽  
Drying Curves

Onion processing waste (OPW) was dried in a convective hot-air laboratory scale dryer at 50, 60, 70 and 80ºC. The effect of drying temperature on the drying characteristics and on the total phenolic and total flavonoid content of dried samples was determined. Three mostly used models were applied for fitting the experimental drying curves. The results indicated that the constant rate-drying period was not observed and that the logarithmic model was the most suitable for fitting the experimental drying kinetic data. The drying temperature significantly affected the total phenolic and total flavonoid content of dried OPW. The values of effective diffusivity were calculated and the determined value of activation energy was 28.05 kJ/mol.

scholarly journals LFER and the Effect of Temperature on Oxyanion Adsorption by Goethite

2019 ◽  
Vol 98 ◽  
pp. 10001 ◽  
Author(s):  
Anna Dabizha ◽  
Nataliya Vlasova ◽  
Michael Kersten
Keyword(s):  
Free Energy ◽  
Linear Relationship ◽  
Gibbs Free Energy ◽  
Surface Complexation ◽  
Equilibrium Adsorption ◽  
Effect Of Temperature ◽  
Complexation Reaction ◽  
Temperature Dependent ◽  
Deprotonation Reaction ◽  
Oxyanion Adsorption

A linear relationship between the Gibbs free energy, ΔGr,H+, of the aqueous complex deprotonation reaction, and the Gibbs free energy, ΔGr,ads, of bidentate surface complexation reaction of oxyanions was derived from modelling of temperature dependent batch equilibrium adsorption experiments. As exemplified in this study, this relationship may be exploited to predict temperature-dependent adsorption behavior of oxyanions not yet known such as pertechnetate.

scholarly journals Thermodynamic properties and drying kinetics of Bauhinia forficata Link leaves

2017 ◽  
Vol 21 (1) ◽  
pp. 61-67 ◽  
Author(s):  
Fernanda P. da Silva ◽  
Valdiney C. Siqueira ◽  
Elton A. S. Martins ◽  
Fábio M. N. Miranda ◽  
Rogerio M. Melo
Keyword(s):  
Free Energy ◽  
Diffusion Coefficient ◽  
Thermodynamic Properties ◽  
Mathematical Models ◽  
Gibbs Free Energy ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Drying Kinetics ◽  
Drying Process ◽  
Bauhinia Forficata

ABSTRACT The aim of this study was to determine the effective diffusion coefficient and the thermodynamic properties of Bauhinia forficata Link leaves, considering two forms of thickness measurements and to describe the process by fitting mathematical models. The leaves were collected, taken to the laboratory and prepared to start the drying process in which four temperatures (40, 50, 60 and 70 °C) were applied. After the drying process, the effective diffusion coefficient was determined through the theory of diffusion in liquid, allowing to obtain the values of the activation energy, enthalpy, entropy and Gibbs free energy. The description of the drying process was performed by setting the thirteen mathematical models used to represent constant drying of agricultural products. The Valcam model was selected to represent the drying kinetics B. forficata Link. Increased temperature promotes: decreasing enthalpy and entropy; increasing Gibbs free energy and effective diffusion coefficient. The effective diffusion coefficient is higher when the rib thickness is considered; thus, it is recommended to standardize and/or specify the points of measurement of leaf thickness.

scholarly journals Effects of Temperature and Steeping Time on the Proximate Compositions and Selected Physical Properties of Soybean Flour

2020 ◽  
Vol 17 (1) ◽  
pp. 40-46
Author(s):  
E.G. Ikrang ◽  
J.U. Okoko ◽  
M.M. Akwa
Keyword(s):  
Particle Size ◽  
Physical Properties ◽  
Bulk Density ◽  
Three Dimensional ◽  
Computer Software ◽  
Angle Of Repose ◽  
Effect Of Temperature ◽  
Soybean Flour ◽  
Crude Fibre ◽  
Drying Temperature

A study to investigate the effect of temperature (80, 85, 90, 95, and 100oC) and steeping time (12, 15, 18, 21, and 24 hours) on the proximate composition (ash, crude fibre, fat , protein, and carbohydrate) values (%) and physical properties (bulk density, packed density (g/ml), angle of repose (degrees), and particle size (μm)) on soybean flour was conducted. Response surface Methodology (RSM) was used for the work. Central Composite Design in Design Expert (version 6.0, 2002, Minneapolis, United States) computer software package was used to design the experiment. Analysis was also done and all results were presented with a three dimensional plot. The results showed that the moisture content of the soybeans flour ranged from 3.26 – 7.35, 3.40 – 4.50 for ash, 3.15 – 4.82 for crude fibre, 31.32 – 35.21 for protein, 19.37 – 22.65 for fat, and 29.66 – 35.19% for carbohydrate. Angle of repose for soybeans flour samples ranged from 33.15 – 38.16o, bulk density varied between 0.30-0.36, packed density varied between 0.52 – 0.57g/ml and particle size distribution varied between 0.44 – .98μm for the different samples. It was observed that longer steeping time and drying temperature resulted to an increase in the protein content and decrease in crude fibre content. Conversely shorter steeping time and lower drying temperature resulted in an increase in the fat content. A nine-point hedonic scale on sensory and acceptability tests showed that sample soaked for 24 hours and dried at 90oC was most preferred in taste and overall acceptability. Keywords: Soybean flour; packed density; angle of repose; steeping time, temperature.

scholarly journals Isotherms and thermodynamic properties of water adsorption in ‘Cumari-do-Pará’ pepper seeds

2020 ◽  
Vol 24 (4) ◽  
pp. 280-285 ◽  
Author(s):  
Karen C. Rodrigues ◽  
Hellismar W. da Silva ◽  
Isneider L. Silva ◽  
Samuel G. F. dos Santos ◽  
Daniel P. da Silva ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Latent Heat ◽  
Adsorption Isotherms ◽  
Water Adsorption ◽  
Gravimetric Method ◽  
Design And Optimization ◽  
Differential Enthalpy ◽  
The One ◽  
Estimated Error

ABSTRACT Studies related to water sorption in seeds are essential for the design and optimization of storage systems. The objective of this research was to determine and model the adsorption isotherms and calculate the latent heat of water vaporization, differential enthalpy and entropy, the isokinetic theory and Gibbs free energy for ‘Cumari-do-Pará’ pepper seeds. The equilibrium moisture contents were obtained by the static gravimetric method at temperatures of 30, 35 and 40 °C and water activities between 0.290 and 0.900 (decimal). The Chen-Clayton model is the one that best represents the water adsorption isotherms in ‘Cumari-do-Pará’ pepper seeds under the studied conditions, with 9.94% mean relative error, 0.40 mean estimated error and random distribution of residuals. The latent heat of vaporization ranged from 2,555.669 to 3,162.180 kJ kg-1. The enthalpy, entropy and Gibbs free energy increase with the reduction in the equilibrium moisture content of the seeds. The isokinetic theory is valid for the adsorption process.

scholarly journals Mathematical Modeling of Thin-Layer Drying Kinetics of Piper aduncum L. Leaves

2019 ◽  
Vol 11 (8) ◽  
pp. 225
Author(s):  
Wellytton Darci Quequeto ◽  
Valdiney Cambuy Siqueira ◽  
Geraldo Acácio Mabasso ◽  
Eder Pedroza Isquierdo ◽  
Rafael Araujo Leite ◽  
...  
Keyword(s):  
Activation Energy ◽  
Free Energy ◽  
Diffusion Coefficient ◽  
Gibbs Free Energy ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Drying Kinetics ◽  
Thin Layer Drying ◽  
Piper Aduncum ◽  
Kinetics Of

As well as most agricultural products, some medicinal plants need to go through a drying process to ensure quality maintenance, however each product behaves differently. Therefore, the present study aimed to evaluate the drying kinetics of spiked pepper (Piper aduncum L.) leaves and determine their thermodynamic properties at different drying temperatures in laboratory scale. Leaves with initial moisture content of 78% w.b. (wet basis) were subjected to drying at temperatures of 40, 50, 60 and 70 ºC and air speed of 0.85 m s-1 in an experimental fixed bed dryer. The drying kinetics of the leaves was described by statistical fitting of mathematical models and determination of effective diffusion coefficient and activation energy. Enthalpy, entropy and Gibbs free energy were also evaluated for all drying conditions. It was concluded that, among the models evaluated, only Midilli and Valcam can be used to represent the drying of Piper aduncum leaves; the first for the two highest temperatures (60 and 70 ºC) and the second for 40 and 50 ºC. The activation energy was approximately 55.64 kJ mol-1, and the effective diffusion coefficient increase with the elevation of temperature. The same occurs with the values of Gibbs free energy, whereas the specific enthalpy and entropy decrease.

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