Comportamento higroscópico de partes aéreas de pimenta-de-macaco (Piper aduncum L.)

Silva, Carolina de Lourdes Oliveira Cruz e; Faria, Lênio José Guerreiro de; Costa, Cristiane Maria Leal

doi:10.1590/1807-1929/agriambi.v19n4p376-381

Cited by 8 publications

(5 citation statements)

References 17 publications

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“…Since the first condition was found here, the water sorption mechanism of rice in the husk is enthalpy controlled. This result is in agreement with those found by several researchers (Goneli et al, 2013;Martinez-Monteagudo & Salais-Fierro, 2014;Nicoleti et al, 2015;Silva et al, 2015;Oliveira et al, 2017).…”

Section: Resultssupporting

confidence: 94%

Thermodynamic Properties of Sorption of Rice in the Husk

et al. 2018

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This study aimed to determine the thermodynamic properties of sorption processes (desorption and adsorption) of rice in the husk, cv. Urucuia. A static-gravimetric method was used to reach equilibrium moisture content at different temperatures (10, 20, 30, 40, and 50 °C ± 1°C) and relative humidity levels (10, 30, 50, 70, and 90 % ± 2%). A decrease in moisture content led to an increment of the integral isosteric heat of sorption, indicating a higher demand for energy to remove moisture from the product. Differential entropy of sorption decreased along with a moisture content increment, with higher values for desorption. This indicates a higher mobility of water molecules during desorption if compared to adsorption. Gibbs free energy decreased with increasing temperature in both processes, with positive values for desorption (endothermic process), and negative for adsorption (exothermic process). The enthalpy-entropy compensation theory is valid for both sorption phenomena (desorption and adsorption) of rice in the husk, being both processes enthalpy controlled.

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Section: Resultssupporting

confidence: 94%

Thermodynamic Properties of Sorption of Rice in the Husk

et al. 2018

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“…Applying the compensation theory implies that only one reaction mechanism is followed by all members of the reactive series, and the existence of a single mechanism suggests that the food microstructure is stable and does not undergo any change during moisture sorption (McMINN et al, 2005). These results are in agreement with several researchers who have applied the isokinetic theory to sorption in several products, concluding that the sorption phenomenon is controlled by enthalpy (CLADERA-OLIVEIRA et al, 2008;GONELI et al, 2013GONELI et al, , 2016MARTINEZ-MONTEAGUDO;SALAIS-FIERRO, 2014;MOREIRA et al, 2008;NICOLETI et al, 2015;SILVA et al, 2015;VEGA-GÁLVEZ et al, 2014;TUNÇ;DUMAN, 2007).…”

Section: Resultssupporting

confidence: 83%

Thermodynamic properties of water desorption in lettuce seeds

Zeymer

Corrêa

Oliveira

et al. 2018

SCA

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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. Key words: Differential enthalpy. Differential entropy. Enthalpy-entropy compensation theory. Equilibrium moisture content. Gibbs free energy. Isosteric heat. ResumoO conhecimento da movimentação das moléculas de água dentro do material é importante para o correto estudo das interações entre a água e os componentes químicos dos produtos agrícolas. O cálculo das propriedades termodinâmicas relata essa necessidade, sendo fonte de informação para projetar equipamentos de secagem, calcular a energia requerida nesse processo e avaliar os fenômenos físicos que ocorrem na superfície dos alimentos. Diante da importância do assunto, o objetivo do presente trabalho foi determinar as propriedades termodinâmicas do processo de dessorção de água em sementes de alface. As sementes de alface possuíam teor de água inicial de 9,3% (b.s. equilíbrio das sementes foi determinado pelo método estático-gravimétrico para diferentes valores de temperatura (10, 20, 30, 40 e 50 ± 1 °C) e atividade de água (entre 11 e 96%), em três repetições. De acordo com os resultados encontrados, observou-se que com o aumento do teor de água de equilíbrio, ocorre redução da energia necessária para a evaporação da água nas sementes de alface, sendo que os valores do calor isostérico integral de dessorção, na faixa de teor de água de 2,1 a 21,2% (b.s.), variaram de 4164,89 a 2477,43 kJ kg -1 ...

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“…The isokinetic temperature for water desorption was 520.91 K, ranging from 563.58 to 478.25 K. The calculated harmonic mean was 297.73 K, which was different from the described isokinetic temperatures, confirming enthalpyentropy compensation and showing that enthalpy controls the process. These results are in line with those of other studies by several researchers, who used the isokinetic theory for different agricultural products (Oliveira et al, 2014;Sousa et al, 2015;Silva et al, 2015;Resende et al, 2017;Corrêa et al, 2017).…”

Section: Resultssupporting

confidence: 92%

Fittings of Adsorption Isotherm Models and Thermodynamic Properties of Urunday Seeds

et al. 2020

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This study aimed to obtain and evaluate thermodynamic properties and hygroscopic equilibrium isotherms of urunday seeds as a function of air relative humidity and temperature, as well as identify the best-fitted mathematical models for adsorption phenomenon. A static-gravimetric method was used to obtain hygroscopic equilibrium moisture content. Seeds were placed in airtight containers with different saturated saline solutions for relative humidity control. These were then kept in BOD incubator chambers at 10, 20, 30, and 40 ºC. Hygroscopic equilibrium moisture content decreased as temperature increased, for the same water activity. The Sigma-Copace model best-fitted seed adsorption data for equilibrium water activity intervals between 0.1129 and 0.8232 (dry basis). Both vaporization latent-heat and differential sorption entropy increased with decreasing hygroscopic equilibrium moisture content. Adsorption process in urunday seeds was controlled by enthalpy.

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Comportamento higroscópico de partes aéreas de pimenta-de-macaco (Piper aduncum L.)

Cited by 8 publications

References 17 publications

Thermodynamic Properties of Sorption of Rice in the Husk

Thermodynamic Properties of Sorption of Rice in the Husk

Thermodynamic properties of water desorption in lettuce seeds

Fittings of Adsorption Isotherm Models and Thermodynamic Properties of Urunday Seeds

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