Evaluation of thermodynamic properties and antioxidant activities of Achachairu (Garcinia humilis) peels under drying process

Abstract

The aim of this study was to evaluate the effect of temperature on the drying kinetics of achachairu peels. Empirical and diffusive models were used to describe the drying kinetics and the thermodynamic properties of the process. Both fresh and dehydrated samples were characterized according to their bioactive compounds and antioxidant activity. The drying was carried out in an air circulation oven at a speed of 1.5 m s−1 at temperatures ranging from 40 to 80°C. Parameters of the effective diffusivity and activation energy were calculated considering the first six terms of Fick's model, and the thermodynamic properties are as follows: enthalpy, entropy and Gibbs free energy. Total phenolic compounds, antioxidant activity by ABTS•+ and DPPH•, and total tannins using aqueous and hydroalcoholic extracts were analysed for both fresh peels and the dehydrated. Page's model was considered to be the most appropriate for describing the drying process that occurred at a decreasing rate from the initial phases until the end of the process; Fick's model showed a higher diffusivity value at a temperature of 80°C. The activation energy of the process ranged from 27.773 to 27.569 kJ mol−1 depending on the number of terms used in Fick's model. The thermodynamic properties indicated that the process is endothermic and not spontaneous. The extraction process using solvents with different polarities (water and ethanol) enabled the extraction of phenolic compounds; however, the extraction by 'AE' revealed superior results for AA‐ABTS•+, TT and AA‐DPPH•, the latter not being capable of identifying differences in the fresh sample.

Effects of hydrothermal pretreatments on thermodynamic and technological properties of red bean starch

“…This translates into a linear increase in the mass transfer coefficient with respect to the increase in drying air temperature, as observed by Almeida, Santos, Alves, and André (2020) and Santos et al (2019). According to Goneli, Vieira, Vilhasanti, and Gonçalves (2014) when there is an increase in temperature, water viscosity, which measures the flow resistance, decreases.…”

“…obtained lower values for (h), 1.84 to 2.11 Â 10 À6 m min À1 for drying red rice starch when applying HP at a fixed temperature of 50 C. It is possible to see that for red bean starch, HP was more effective in reducing drying time due to the higher value of the mass transfer coefficient. This translates into a linear increase in the mass transfer coefficient with respect to the increase in drying air temperature, as observed byAlmeida, Santos, Alves, andAndré (2020) andSantos et al (2019). According toGoneli, Vieira, Vilhasanti, and Gonçalves (2014) when there is an increase in temperature, water viscosity, which measures the flow resistance, decreases.…”

Application of pulsed electric field and drying temperature response on the thermodynamic and thermal properties of red rice starch (Oryza Sativa L.)

“…Increasing the temperature of the material also increases the diffusivity value leading to a higher rate of moisture diffusion (Koua, Koffi, & Gbaha, 2019). It translates to the h increasing linearly with the temperature of the drying air as observed by Almeida, Santos, Alves, and André (2020) and D. D. C. Santos et al (2019). According to Goneli, Vieira, Vilhasanti, and Gonçalves (2014), when there is an increase in temperature, the viscosity of the water, which measures the flow resistance, decreases.…”

Heat Pump Drying of Kelp (Laminaria japonica): Drying Kinetics and Thermodynamic Properties

“…Hu et al [11] studied the heat pump drying kinetics characteristics of kelp knot and found that the Page model could effectively fit the changing rule of moisture content with time, but the drying of spreading kelp leaves and their kinetics and thermodynamic properties were unclear. Tunckal et al [14] fitted the moisture ratio of banana slices during heat pump drying with the Midilli and Kucuk model, and the effective moisture diffusivity values were calculated to be between 1.12 × 10 −10 and 1.64 × 10 −10 m 2 /s over a temperature range of 37-42 • C. Almeida et al [21] calculated the effective moisture diffusivity, activation energy, and the thermodynamic properties of Achachairu (Garcinia humilis) peels under the drying process. Their results provided important information about the moisture migration and the required energy during the process.…”