Modelagem e propriedades termodinâmicas na secagem de morangos

Oliveira, Gabriel Henrique Horta de; Aragão, Dayane Mayara Santos; Oliveira, Ana Paula Lelis Rodrigues de; Silva, Marley Garcia; Gusmão, Anne Caroline Araújo

doi:10.1590/1981-6723.5315

Cited by 26 publications

(26 citation statements)

References 23 publications

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“…The enthalpy changes provide a measure of the energy variation that occurs in the interaction of the water molecules with the constituents of the product during the sorption processes. Entropy is associated with the binding or repulsion of the water molecules of food components in the system and is associated with the spatial arrangement of the water product relationship (Oliveira et al, 2015). Therefore, entropy characterizes the degree of order or disorder.…”

Section: Introductionmentioning

confidence: 99%

Drying kinetics and thermodynamic properties of boldo (Plectranthus barbatus Andrews) leaves

Silva¹,

Santos²,

Silva³

et al. 2019

Científica

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Boldo leaves are used as medicinal plants by the Brazilian population. Among several factors that contribute to the proper storage of this product, we highlight the drying process, which is fundamental to reduce its moisture content, aiming to maintain phytotherapic characteristics. Different works involving the drying of leaves were carried out in the last years. However, there is not much information related to the drying process related to boldo leaves. This work evaluates drying kinetics at temperatures of 20, 40 and 60 °C, as well as determines thermodynamic properties: enthalpy, entropy and Gibbs free energy. Forced air circulation ovens were used for thin layer drying of leaves. The leaves, uniformly cut rectangular, were weighed periodically until hygroscopic equilibrium. Several mathematical models were fitted to the experimental data to characterize the drying processes, using the following statistical criteria: coefficient of determination (R²), mean standard error (SE), chi-square (χ²), and residue distribution. According to the criteria used, Modified Henderson and Pabis was the model that best represented the drying kinetics of boldo leaves. The activation energy for the drying of boldo leaves was 17.969 kJ mol-1. Both enthalpy and entropy decreased with increasing drying air temperature, while Gibbs free energy increased.

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Section: Introductionmentioning

confidence: 99%

Drying kinetics and thermodynamic properties of boldo (Plectranthus barbatus Andrews) leaves

Silva¹,

Santos²,

Silva³

et al. 2019

Científica

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“…According to Oliveira et al (2015), drying is one of the most well-known and used technologies in the world for ensuring the quality and stability of fresh products during shelf-life. Reduction in the moisture content of material by drying reduces biological activity and chemical or physical changes during the post-harvest procedures and until final consumption.…”

Section: Introductionmentioning

confidence: 99%

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 positive value is characteristic of adding energy during the drying process, relating the drying of garlic to an endergonic reaction . OLIVEIRA et al (2015), CORRÊA et al (2010) andMARTINS et al (2015) showed similar values for strawberry, coffee cherry and timbó leaf drying studies, respectively. According to OLIVEIRA et al (2015), a non-spontaneous reaction is related to the enthalpy and entropy values, described above, as these reactions occur only when changes in enthalpy are positive and changes in entropy are negative; the variations of these parameters have a positive effect, but the variations are larger for the enthalpy than for the entropy; the changes in the parameters themselves are negative, and the enthalpy change is smaller than the entropy.…”

Section: Thermodynamic Parametersmentioning

confidence: 55%

“…Associating this parameter to the other coefficients observed, it can be stated that for all the temperatures examined, the Midilli model will satisfactorily reflect drying performance, as shown in Table 3. The Midilli model, in general, is the second best fit to agricultural products described by SILVA et al (2015) in drying jenipapo leaves and MELO et al (2015) in drying peppers. However, RADÜNZ et al (2011) discuss that the adjustment of the mathematical model depends upon the plant species, necessitating individual studies at various temperatures and for confirmation.…”

Section: Discussionmentioning

confidence: 99%