Effect of drying methods on drying kinetics, energy features, thermophysical and microstructural properties of Stevia rebaudiana leaves

Autor: Kong Ah-Hen, Liliana Zura-Bravo, Roberto Lemus-Mondaca, Karina Di Scala
Rok vydání: 2021
Předmět:
Zdroj: Journal of the Science of Food and Agriculture. 101:6484-6495
ISSN: 1097-0010
0022-5142
DOI: 10.1002/jsfa.11320
Popis: BACKGROUND Stevia leaves were subjected to convective hot-air, infrared and vacuum drying at 40, 60 and 80 °C, followed by an assessment of thermophysical properties and microstructure, along with drying kinetics modelling and evaluation of energy features for all drying operations. RESULTS Effective moisture diffusivity (Deff ) showed dependency on temperature with values ranging from 1.08 × 10-12 to 7.43 × 10-12 m2 s-1 for convective drying, from 0.71 × 10-12 to 6.60 × 10-12 m2 s-1 for infrared drying, and from 1.29 × 10-12 to 5.39 × 10-12 m2 s-1 for vacuum drying. The thermal properties of the dried Stevia leaves under different drying conditions showed values of density, specific heat, thermal diffusivity, thermal conductivity and thermal effusivity ranging from 95.6 to 116.2 kg m-3 , 3050 to 3900 J kg-1 K-1 , 4.28 × 10-7 to 5.60 × 10-7 m2 s-1 , 0.16 to 0.23 W m-1 K-1 and 244 to 305 W s0.5 m-2 K-1 , respectively. As for microstructure, convective hot-air drying showed better preserved leaf characteristics, compared to infrared- and vacuum-drying, whereby scanning electron microscopy (SEM) image analysis also revealed noticeable differences at higher temperatures. Statistical analysis showed that the Midilli-Kucuk model fitted best the experimental data of drying curves (0.961
Databáze: OpenAIRE
Externí odkaz: