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

Abstract

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.

Avaliação Dos Parâmetros Termodinâmicos E Cinéticos De Cenouras Submetidas a Secagem Convectiva

“…Observando os valores de entalpia notou-se que ela diminui com o aumento da temperatura, indicando que é necessária uma menor quantidade de energia para a secagem ocorrer em temperaturas mais altas, indicando também que o processo é endotérmico. Costa et al (2016) …”

Drying of macaw palm fruits and its influence on oil quality

“…Heat and mass transfers must be well understood to reach a maximum efficiency, both economically and technically (COSTA et al, 2016). Therefore, the simulation and theoretical information related to the physiological, chemical, and physical variations of agricultural products are of paramount importance in the development, evaluation, and optimization of dryers.…”

“…These models may be empirical or phenomenological. Empirical models are generally simple and easy to apply since they are based on experimental data, dimensional and statistical analyses (COSTA et al, 2016). The phenomenological ones, however, are based on most complex theories and laws.…”

Thin layer modeling and determination of thermodynamic properties of tomato slices during hot air drying

“…In order to analyze the drying behaviour of an agricultural product during drying process, the study of its kinetics in thin layers is essential [5,6,7,8]. Mathematical modeling involves predicting and simulating drying behaviour of certain parameters and processes in a unified manner regardless of the control mechanism, through empirical and phenomenological models [9,10]. Several mathematical models such as the Midilli et al model, Page model, Newton model, Fick's-diffusion model, Logarithmic model, Henderson and Pabis model etc.…”

“…These models which describe the characteristics of a particular product being dried are used to estimate the drying time of several products and also to generalize drying curves needed for dryer design and process optimization. The study of thermodynamic properties in the drying process of agricultural products aims to proffer solutions to problems related to stability and optimization of process conditions [10,11]. It is necessary for optimal designing and dimensioning of crop dryers and other devices in various processes of preservation of product quality as well as in the proper understanding and provision of information on energy exchanges between one state of equilibrium to the other [10,12].…”