Water sorption isotherms of starch powders. Part 2: Thermodynamic characteristics

Al-Muhtaseb, Ala’a H.; McMinn, W.A.M.; Magee, T.R.A.

doi:10.1016/s0260-8774(03)00202-4

Cited by 176 publications

(157 citation statements)

References 19 publications

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“…The entropy of sorption of preconditioned pressure parboiled brown rice as a function of moisture content is shown in Figure 4, from this figure it can be observed that entropy of sorption decreased with increasing moisture content, similar trends have been reported for differential entropy of starch powders [39], pepper [40], crushed chillies [8] but for rice stored under controlled humidity chamber reported that sorption entropy decreased with increasing moisture content in desorption process but in adsorption process increased up to certain moisture content later it decreased with increasing moisture content [10]. Differential entropy increased with increasing salt concentration ( Figure 4) from this we can reveal that number of sorption sites were more at higher salt concentration at a specific energy level.…”

Section: Net Isosteric Heat Of Sorption and Sorption Entropysupporting

confidence: 80%

Moisture Sorption Isotherm of Preconditioned Pressure Parboiled Brown Rice

M¹,

Sk²

2015

J Food Process Technol

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The pressure parboiling of paddy was carried out at 294.204 kPa for 7 min and preconditioning of brown rice was carried out in fluidized bed dryer at 60-80°C. The moisture sorption isotherms of pressure parboiled preconditioned brown rice at different salt concentrations (0, 2, 3, 3.5 and 4%) were obtained at 20 ± 1°C, 25 ± 1°C, and 30 ± 1°C. The experimental data of sorption isotherm were fitted with some of sorption models (GAB, MGAB, MCPE, MOSE, MHEE, and MHAE models). According to the statistical results, the MGAB model gave the best fit to the experimental sorption data and MHAE model was the least adequate. Sorption isotherm data were used to determine the some thermodynamic functions. The net isosteric heat of sorption was determined from the best fitting equation using the Claussius-Calpeyron equation. The net isosteric heat of sorption decreased with increasing moisture content and increased with increasing salt concentration same trend was observed in entropy of sorption. The spreading pressure increased with increasing water activity and salt concentration and decreased with increasing temperature. The net integral enthalpy decreased with increasing moisture content and increased with increasing salt concentration and reverse trend was observed in integral entropy.

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Section: Net Isosteric Heat Of Sorption and Sorption Entropysupporting

confidence: 80%

Moisture Sorption Isotherm of Preconditioned Pressure Parboiled Brown Rice

M¹,

Sk²

2015

J Food Process Technol

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“…The basic problem is the designation of the entropy of adsorption, which is usually overlooked in this type of work. These capabilities only exist when the use of the thermodynamic equilibrium constant is skipped, e.g., (Madamba et al 1996;Beristain et al 1996;Al-Muhtaseb et al 2004, 2007Pedro and Babas 2005;Ramesh et al 2005;Tang et al 2006;Palomino et al 2008;Musa et al 2010;Loto et al 2012) as these cases do not require comments, and for non-pressure processes, when P/P o < 1.…”

Section: Purpose and Scope Of Studiesmentioning

confidence: 99%

Enthalpy–entropy compensation for isosteric state adsorption at near ambient temperatures

Mianowski

Urbańczyk

2017

Adsorption

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List of symbols AbstractThe adsorption process at near ambient temperatures indicated that the EEC (enthalpy-entropy compensation) is affected by three basic thermodynamic values: ∆H, ∆S and T. The consequence is that it is possible to determine an isosteric straight (symbol H − S) without experimental studies based on the slope coefficient T iso , which is the constant arising from the expected temperature range (about 0-60 °C). Therefore, EEC curves can be obtained by appropriate modification of the temperature range. In the case of entropy of adsorption, the decisive influence is the entropy of gas. For visualization and characterization of this impact, we proposed resolute pointer µ (Eq. 25), through which it is observed that for small values of the equilibrium vapor pressure, as P → 0, there are significant deviations from the isosteric straight H − S. The case where P → P 0 followed a gradual grouping of experimental data in accordance with the relationship with H − S. We used the three-parameter equation for exothermic processes. For the extrapolated conditions, the so-called point of zero adsorption represented the enthalpy and entropy of adsorption, whose values are analogous to previous results in the literature, which can be considered an appropriate analytical method to determine these two thermodynamic values.

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“…Na fase inicial de adsorção, na superfície do amido existem sítios de adsorção altamente polares nos quais as moléculas de água estão fortemente ligadas em forma de monocamada. Aqui, a energia de interação molécula de água/ amido é maior que a energia de interação entre moléculas de água pura (λ vap = 43,35 kJ/mol) (AL-MUHTASEB; MAGEE, 2004;ROMERO et al, 2005;FASINA;2006 menor quantidade de sítios de adsorção altamente polares na sua superfície e, portanto, disponibiliza menor energia para a interação com as moléculas de água, o que o torna um produto menos higroscópico que os amidos acima referidos.…”

Section: Entalpia E Entropia Diferenciais De Adsorçãounclassified

“…Tendências semelhantes foram observadas para amido de batata e amidos com elevados teores de amilose e de amilopectina (AL-MUHTASEB;MAGEE, 2004) A regressão correspondente ao amido de rizomas do lírio-do-brejo foi (Equação 17): 9,458 237 ,877. S R 0,997 0,277 …”

Section: Entalpia E Entropia Diferenciais De Adsorçãounclassified

Propriedades termodinâmicas de adsorção de água do amido de rizomas do lírio-do-brejo (Hedychium coronarium)

Ascheri¹,

Moura²,

Ascheri³

et al. 2009

Ciênc. Tecnol. Aliment.

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GROTH, 1991;MACEDO, 1997).No Brasil, o lírio-do-brejo é considerado uma planta exótica invasora e atualmente vêm se estudando o manejo e o controle desta praga, uma vez que a conseqüência negativa sobre as espécies nativas torna esta planta daninha nos locais onde prolifera (SANTOS; PEDRALLI; MEYER, 2005).Apresenta uma ampla utilização, principalmente farmacológica e ornamental (AGAREZ; PEREIRA; ATIDIO, 1994), no entanto, apesar do teor de amido nos rizomas do lírio-do-brejo, não há na literatura estudos sobre este amido natural, tornando-se necessárias pesquisas sobre suas propriedades termodinâmicas de adsorção de água aplicadas ao processo de secagem do amido.As propriedades termodinâmicas de adsorção de água são fundamentais para a análise de projetos de equipamentos em AbstractThermodynamic properties where determined (differential enthalpy, of differential entropy, integral enthalpy, and integral entropy) of the starch of rhizomes of swamp lily through water adsorption isotherms. The isotherms were determined in water activities in the range of 0.11 to 0.84, in temperatures ranging from 30 to 50 °C. The GAB equation which fits well to the experimental isotherms was used to estimate the properties of thermodynamic adsorption. The slight reversal of the isotherms indicates damaged starch. The enthalpy and entropy differential gap increased with the decrease in moisture and correlated to each other confirming the chemical linear compensation. An exponential model type Y = b.e (a/X e ) described adequately the dependence of these properties differential on the moisture content of balance. The integral enthalpy and entropy increased continuously with the moisture content of balance but presented negative values for the integral entropy. These thermodynamic properties of water adsorption showed that the starch extracted from the rhizomes of swamp lily has low hygroscopicity despite the occurrence of damaged starch granules.

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Water sorption isotherms of starch powders. Part 2: Thermodynamic characteristics

Cited by 176 publications

References 19 publications

Moisture Sorption Isotherm of Preconditioned Pressure Parboiled Brown Rice

Moisture Sorption Isotherm of Preconditioned Pressure Parboiled Brown Rice

Enthalpy–entropy compensation for isosteric state adsorption at near ambient temperatures

Propriedades termodinâmicas de adsorção de água do amido de rizomas do lírio-do-brejo (Hedychium coronarium)

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