Drying kinetics and thermodynamic properties of bitter melon (Momordica charantia L.) leaves

Abstract

Bitter melon (Momordica charantia L.) is a versatile plant that can be consumed as a food and has therapeutic applications. Studying its drying process is important to maintain their leaf quality during storage. The objective of this study was to evaluate the drying kinetics of bitter melon leaves and determine their thermodynamic properties. The leaves were placed in polyethylene trays and subjected to drying in an oven at temperatures of 20, 30, 40, and 50 °C until reaching hygroscopic equilibrium. The experimental data were fitted to several non-linear regression models to characterize the drying process. The Arrhenius model was used to obtain the coefficients of diffusion and the activation energy, which were used to calculate the enthalpy, entropy, and the Gibbs free energy. Midilli and Page were the best models to represent the drying kinetics of bitter melon leaves at temperatures of 20, 30, 40, and 50 °C. Increases in the drying air temperature increased the Gibbs free energy and water diffusivity in the interior of the leaves. Enthalpy and entropy decreased as the temperature was increased.

Drying kinetics and thermodynamic properties of Uzun pistachios dried by convective drying

“…The higher temperature resulted in a decline in the Δ S values for the two samples studied. This was expected, since decreases in temperature caused in less water molecule excitation, hence increasing the order of the pistachios (Silva et al, 2020). The presence of chemical adsorption or structural modifications to the adsorbent is ascribed to the negative values of the Δ S (Alves et al, 2021; Moreira et al, 2008).…”

“…Δ G increased as the temperature increased and the Δ G values were positive, which means the drying of pistachio samples was not spontaneous under the conditions of this study (Silva et al, 2019). Additionally, this is an endothermic reaction, requiring an additional energy source to raise the energy level and convert the reagents to the vapor state (Ong et al, 2013; Silva et al, 2020). With increasing the temperature, the decrease in Δ H and Δ S and increase in Δ G have been observed in various agricultural products such as jabuticaba peel (Costa et al, 2016), boldo leaves (Silva et al, 2019), bacaba pulp (Morais et al, 2019), bitter lemon (Silva et al, 2020), trapia residues (Moura et al, 2021), and baru almond flours (Alves et al, 2021).…”

Thermal Degradation of Carotenoids from Jambu Leaves (Acmella oleracea) during Convective Drying

“…The results for the coefficient of determination (R 2 ), mean relative error ( P ), mean estimated error (SE), and chi square test (χ 2 ) demonstrate that only the Page [ 15 ] model presents a proper fit to describe the drying process. In a study carried out with Momordica charantia L. leaves, the Page model was also the one that best represented the drying kinetics [ 25 ]. The drying coefficient k increases with increasing temperature, indicating that the Page model is related to the effective diffusivity.…”

Thermodynamic properties and bioactive compounds of mandacaru dried waste

“…Entropy measures the degree of disorder of the molecules in the system, and so the negative values were an indication that during drying the water content decreased and therefore the movement of the water molecules reduced due to the smaller number of sites available and structural alterations to the adsorbent (Corrêa et al, 2011; Silva et al, 2020; Yildirim, 2018).…”

“…The enthalpy (ΔH) showed positive values indicating an endothermic system, typical of drying processes, where energy is transferred from the air to the product in the form of heat. There was a reduction in ΔH as the temperature rose, due, according to Entropy measures the degree of disorder of the molecules in the system, and so the negative values were an indication that during drying the water content decreased and therefore the movement of the water molecules reduced due to the smaller number of sites available and structural alterations to the adsorbent (Corrêa et al, 2011;Silva et al, 2020;Yildirim, 2018).…”