Monolayer moisture, free energy change and fractionation of bound water of red chillies

Kaleemullah, S.; Kailappan, R.

doi:10.1016/j.jspr.2005.12.001

Cited by 45 publications

(34 citation statements)

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“…Gibbs free energy decreased with increase in temperature and equilibrium moisture content, and in the latter case, it tends to a constant value. This behavior was also observed in previous studies by Sousa et al (2015), Oliveira et al (2014), and Kaleemullah & Kailappan (2007).…”

Section: Resultssupporting

confidence: 90%

“…From Figure 4, it can be observed that the Gibbs free energy in the desorption process was higher compared to the adsorption process at temperatures of 20, 30, and 40 °C, similar to results obtained by Kaleemullah & Kailappan (2007). For a temperature of 50 ºC, the results obtained for the control beans were similar as shown in Figures 4C and 4D indicates that damage effect plays a higher role in terms of energy than temperature for sorption processes below 50 ºC.…”

Section: Resultssupporting

confidence: 81%

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Kinetics of water sorption of damaged bean grains: Thermodynamic properties

Corrêa

Baptestini

Bustos-Vanegas

et al. 2017

Rev. bras. eng. agríc. ambient.

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A B S T R A C TThis 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.Cinética de sorção de água de grãos de feijão danificado: Propriedades termodinâmicas R E S U M OObjetivou-se determinar as propriedades termodinâmicas de grãos de feijão danificados. Foram utilizados grãos com teor de água inicial de 53,85% (b.s.); parte dos grãos foi utilizada para se obter as isotermas de dessorção, enquanto que a outra foi submetida a secagem até o teor de água de 5,26% (b.s.), para que a mesma fosse submetida ao processo de adsorção. Para a indução da danificação foi utilizado um Stein Breakage Tester. Para obter o teor de água de equilíbrio, os grãos foram colocados em câmara climática cujas temperaturas foram de 20, 30, 40 e 50 ± 1 ºC combinadas com umidades relativas de 30, 40, 50, 70 e 90 ± 3%. Na dessorção, os grãos danificados apresentaram menor entalpia diferencial quando comparados com a testemunha enquanto o inverso foi observado na adsorção. A danificação mecânica provocou a formação de um número maior de sítios disponíveis de sorção, resultando em maiores valores de entropia diferencial na adsorção e menores valores na dessorção quando comparados com a testemunha. A danificação mecânica não teve efeito sobre a energia livre de Gibbs.

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 81%

Kinetics of water sorption of damaged bean grains: Thermodynamic properties

Corrêa

Baptestini

Bustos-Vanegas

et al. 2017

Rev. bras. eng. agríc. ambient.

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“…Changes of the Gibbs free energy during water sorption between the product and the environment can be defined as required energy to transfer water molecules from the vapor state to a solid surface, or vice versa. This is the amount of work generated by the system during the adsorption or desorption process (Kaleemullah & Kailappan, 2007).…”

Section: Acta Scientiarum Agronomymentioning

confidence: 99%

<b>Kinetic modeling of water sorption by roasted and ground coffee

et al. 2017

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ABSTRACT. The objective of this study was to model the kinetics of water sorption in roasted and ground coffee. Crude Arabica coffee beans with an initial moisture content of 0.1234 kg w kg dm -1 were used. These beans were roasted to a medium roast level (SCCA # 55) and ground at three particle sizes: coarse (1.19 mm), medium (0.84 mm) and fine (0.59 mm). To obtain the water sorption isotherms and the isosteric heat, different conditions of temperature and relative humidity were analyzed using the dynamic method at 25ºC (0.50, 0.60, 0.70, and 0.80 of RH) and 30°C (0.30, 0.40, 0.50, 0.60, 0.70, and 0.80 of RH) and using the static method at 25ºC (0.332 and 0.438 of RH). The GAB model best represented the hygroscopic equilibrium of roasted coffee at every particle size. Isosteric heat of sorption for the fine particle size increased with increments of equilibrium moisture content, indicating a strong bond energy between water molecules and the product components. The Gibbs free energy decreased with the increase in equilibrium moisture content and with temperature.Keywords: particle size, specific surface, isosteric heat.Modelagem da cinética de sorção de água de café torrado e moído RESUMO. Objetivou-se com este trabalho modelar a cinética de sorção de água pelo café torrado e moído. Foram utilizados grãos de café arábica com teor de água inicial de 0,1234 kg a kg ms -1 , torrados no ponto de torra médio (SCCA # 55), tendo sido estabelecido três níveis granulométricos: grossa (1,19 mm), média (0,84 mm) e fina (0,59 mm). Para a obtenção das isotermas de sorção da água e do calor isostérico, foram analisadas diferentes condições de temperatura e umidade relativa: usando o método dinâmico, 25ºC (0,50; 0,60; 0,70 e 0,80 de UR) e 30°C (0,30; 0,40; 0,50; 0,60; 0,70 e 0,80 de UR); e o método estático, 25ºC (0,332 e 0,438 de UR). Os dados de teor de água no equilíbrio foram correlacionados com modelos matemáticos. O modelo de GAB foi o que melhor representou o equilíbrio higroscópico para a sorção do café torrado nos diferentes níveis granulométricos. O calor isostérico de sorção na granulometria fina aumentou com a elevação do teor de água de equilíbrio indicando forte grau de ligação entre as moléculas de água e o produto. A energia livre de Gibbs diminuiu com o aumento do teor de água de equilíbrio e com a temperatura.Palavras-chave: granulometria, superfície específica, calor isostérico.

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“…According to Dannenberg & Kessler (1988), a substance, in this case water, can have only negative entropy if the degrees of freedom of the movement of translation or rotation are lost. Gibbs free energy is an amount that can be considered as a measurement of work performed by the system in the process of adsorption or desorption (Kaleemullah & Kailappan, 2007). This energy provides a better view on which thermodynamic driving forces influence the reactions.…”

Section: Modelsmentioning

confidence: 99%

Mathematical modeling and determination of thermodynamic properties of jabuticaba peel during the drying process

Costa

Corrêa

Bustos-Vanegas

et al. 2016

Rev. bras. eng. agríc. ambient.

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A B S T R A C TJabuticaba is a fruit native of Brazil and, besides containing many nutritional qualities, it also has a good field for use in products such as flour for cakes and biscuits, juice, liqueur, jelly and others. This study aimed to model the drying kinetics and determine the thermodynamic properties of jabuticaba peel at different drying air temperatures. Ripe fruits of jabuticaba (Myrciaria jaboticaba) were collected and pulped manually. Drying was carried out in a forced-air circulation oven with a flow of 5.6 m s -1 at temperatures of 40, 50, 60 and 70 °C. Six mathematical models commonly used to represent the drying process of agricultural products were fitted to the experimental data. The Arrhenius model was used to represent the drying constant as a function of temperature. The Midilli model showed the best fit to the experimental data of drying. The drying constant increased with the increment in drying temperature and promoted an activation energy of 37.29 kJ mol -1 . Enthalpy and Gibbs free energy decreased with the increase in drying temperature, while entropy decreased and was negative.Modelagem matemática e propriedades termodinâmicas da casca da jabuticaba durante o processo de secagem R E S U M OA jabuticaba é um fruto nativo do Brasil e além de conter muitas qualidades nutricionais também possui bom campo para a utilização em subprodutos como farinhas para bolos e biscoitos, suco, licor, geleia e outros. Objetivou-se modelar a cinética de secagem e determinar as propriedades termodinâmicas de casca de jabuticaba em diferentes temperaturas do ar de secagem. Foram utilizadas jabuticabas maduras, colhidas e separadas da polpa manualmente, da espécie Myrciaria jaboticaba. A secagem foi realizada em estufa de circulação forçada de ar com velocidade de 5,6 m s -1 nas temperaturas de 40; 50; 60 e 70 °C. Seis modelos matemáticos usualmente utilizados para a representação do processo de secagem de produtos agrícolas foram ajustados aos dados experimentais. A relação do tipo Arrhenius foi utilizada para representar a constante de secagem em função da temperatura. O modelo de Midilli foi o que melhor se ajustou aos dados experimentais da secagem. A constante de secagem aumentou com o incremento da temperatura de secagem e proporcionou energia de ativação de 37,29 kJ mol -1 . A entalpia e a energia livre de Gibbs diminuíram com o aumento da temperatura de secagem; já a entropia diminuiu e foi negativa.

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Monolayer moisture, free energy change and fractionation of bound water of red chillies

Cited by 45 publications

References 4 publications

Kinetics of water sorption of damaged bean grains: Thermodynamic properties

Kinetics of water sorption of damaged bean grains: Thermodynamic properties

<b>Kinetic modeling of water sorption by roasted and ground coffee

Mathematical modeling and determination of thermodynamic properties of jabuticaba peel during the drying process

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