Effect of temperature and speed of air dryer on drying kinetic and phenolic compounds of stevia leaf

Author
leila Nateghi
Department of Food Science and Technology, Faculty of Agriculture, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran
10.52547/fsct.18.115.21
Abstract
Stevia is a seasonal herb that contains high levels of phenolic and sugar compounds called stevioside rhabadiosid. Due to the seasonality of this plant, the most suitable method for making it available is using drying methods. Choosing the proper method of plant drying is one of the most important issues in post-harvest operation. Using inappropriate methods can result in the loss of plant organs or the loss of all the effective substances in it. The main objective of this study was to evaluate the effect of temperature and velocity of dryer on drying process, total phenolic compounds and kinetic modeling of stevia leaf drying. For this purpose, air temperature was measured at three levels (45 °C, 55 °C, 70 °C) and air velocity at three levels (0.05 m/s, 1 m/s and 1.5 m/s) for drying Stevia leaves were used. In this research, five models of Pelge math, Weibull, Logarithmic, Page and Khazaei models were used to model the results of stevia leaf drying process.The results showed that the proposed experimental models had a desirable performance in the modeling of the stevia moisture reduction process (R2 ≥ 0.945). By comparing the output values ​​of R2 and RMSE for the models presented, the Page model had better modeling performance than the other four models. In addition, the results showed that in the drying process, the most important factor in controlling the stevia leaf drying rate was the air temperature. Also, the drying time of stevia leaves decreased with increasing temperature and speed of air drying. Dryer temperature has a significant effect on the content of total phenolic compounds. As the air temperature rises from 45 °C to 70 °C, the amount of phenolic compounds of the stevia leaf decreases.
Keywords
Drying Stevia
mathematical modeling
phenol content

Subjects

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Journal of food science and technology(Iran)
Volume 18, Issue 115 - Serial Number 115
September 2021
Pages 259-271