*Article* **Model for Thin Layer Drying of Lemongrass (***Cymbopogon citratus***) by Hot Air**

**Thi Van Linh Nguyen 1,2,\*, My Duyen Nguyen 1, Duy Chinh Nguyen 3, Long Giang Bach 3 and Tri Duc Lam 3**


Received: 7 December 2018; Accepted: 28 December 2018; Published: 4 January 2019

**Abstract:** Lemongrass is a plant that contains aromatic compounds (myrcene and limonene), powerful deodorants, and antimicrobial compounds (citral and geraniol). Identifying a suitable drying model for the material is crucial for establishing an initial step for the development of dried products. Convection drying is a commonly used drying method that could extend the shelf life of the product. In this study, a suitable kinetic model for the drying process was determined by fitting moisture data corresponding to four different temperature levels: 50, 55, 60 and 65 ◦C. In addition, the effect of drying temperature on the moisture removal rate, the effective diffusion coefficient and activation energy were also estimated. The results showed that time for moisture removal increases proportionally with the air-drying temperature, and that the Weibull model is the most suitable model for describing the drying process. The effective diffusion coefficient ranges from 7.64 × 10−<sup>11</sup> m2/s to 1.48 × 10−<sup>10</sup> m2/s and the activation energy was 38.34 kJ/mol. The activation energy for lemongrass evaporation is relatively high, suggesting that more energy is needed to separate moisture from the material by drying.

**Keywords:** lemongrass; *Cymbopogon citratus*; convection drying; mathematical modeling; moisture diffusivity; activation energy
