Hygroscopicity of ‘sucupira-branca’ (Pterodon emarginatus Vogel) fruits

Abstract

A B S T R A C T'Sucupira-branca' (Pterodon emarginatus Vogel) is a tree from 'Cerrado' and stands out mainly for its pharmacological properties; however, there are no technological information about its post-harvest operations. Thus, the aim of this study was to determine the sorption isotherms of 'sucupira-branca' fruits for different air conditions and obtain the values of desorption isosteric heat, depending on the equilibrium moisture content of the product. The equilibrium moisture content of 'sucupira-branca' fruits was determined by dynamic method for temperatures of 25, 30, 35 and 40 °C and water activities for each temperature between 0.270 and 0.775. The models Chung-Pfost, Copace, Modified Halsey, Oswin Modified and Sigma Copace obtained high coefficient of determination (R 2 ) and low chisquare (χ 2 ), relative mean error (P) and estimated mean error (SE), and the Copace model was selected to represent the desorption isotherms. The isosteric heat increases with the reduction of equilibrium moisture content and required more energy to remove water from the 'sucupira-branca' fruit.Higroscopicidade dos frutos de sucupira-branca (Pterodon emarginatus Vogel) R E S U M OA sucupira-branca (Pterodon emarginatus Vogel) é uma árvore do Cerrado e se destaca principalmente por suas propriedades farmacológicas; entretanto, inexistem informações tecnológicas sobre as operações de pós-colheita. Desta forma, objetivou-se, com este trabalho, determinar as isotermas de dessorção dos frutos de sucupira-branca para diferentes condições do ar, bem como obter os valores do calor isostérico de dessorção em função do teor de água de equilíbrio do produto. O teor de água de equilíbrio dos frutos de sucupira-branca foi determinado pelo método dinâmico para temperaturas de 25, 30, 35 e 40 °C e atividades de água para cada temperatura, entre 0,270 a 0,775. Os modelos Chung-Pfost, Copace, Halsey Modificado, Oswin Modificado e Sigma Copace obtiveram elevado coeficiente de determinação (R 2 ) e baixo Qui-quadrado (χ 2 ), erro médio relativo (P) e estimado (SE), sendo o modelo de Copace selecionado para representar as isotermas de dessorção. O calor isostérico aumenta com a redução do teor de água de equilíbrio, sendo relevante maior quantidade de energia para retirar a água dos frutos de sucupira-branca.

Adsorption isotherms and thermodynamic properties of Carthamus tinctorius L. seeds

“…It can be observed that the harmonic mean had values lower than the range of isokinetic temperature, showing that the process is controlled by enthalpy. These results are consistent with those found by several researchers who have successfully applied the isokinetic theory to the sorption of the most diverse products (Hassini et al, 2015;Goneli et al, 2016;Oliveira et al, 2017;Resende et al, 2017;Silva et al, 2018;Campos et al, 2019).…”

“…This occurs because the adsorption heat is a measure of the energy released in the sorption of water in the product (Rizvi, 1995), being considered an indication of the intermolecular forces of attraction between the sorption sites and the water vapor (Wang & Brennan, 1991), so the higher the moisture content of the product, the lower the adsorption heat due to the lower number of bonds between the sorption sites. Oliveira et al (2017), studying the isosteric heat of sucupira-branca (Pterodon emarginatus Vogel) fruits, observed similar behavior for the integral isosteric heat, which ranged from 3,477.54 to 15,375.89 kJ kg -1 within the moisture content range from 10.4 to 4.7% (d.b. ), respectively.…”

Desorption isotherms and isosteric heat of protein hydrolysate from tilapia slaughtering by-product

“…Desorption isotherms are unique for each product (Galdeano et al, 2018) and very important, since, once the breakeven point is known, it can estimate the time needed to reach it, avoiding unnecessary energy expenditure during the drying operations, and provide information about the safe moisture contents (Botelho et al, 2019). In turn, isosteric heat is considered an essential parameter in energy demanded on drying processes because it is related to the amount of energy to remove the free water (Oliveira et al, 2017).…”