ARTICLE pubs.acs.org/IECR
Short-Path-Distillation Process of Lemongrass Essential Oil: Physicochemical Characterization and Assessment Quality of the Distillate and the Residue Products Laura P. Tovar,*,†,§ Glaucia M. F. Pinto,† Maria R. Wolf-Maciel,† Cesar B. Batistella,† and Rubens Maciel-Filho‡ †
Laboratory of Separation Process Development and ‡Laboratory of Optimization, Project and Advanced Control, School of Chemical Engineering, State University of Campinas, 13083-852 Campinas, Brazil ABSTRACT: Short-path distillation (SPD), a special high-tech thermal separation technique operating at high vacuum, was used in order to increase the citral concentration in lemongrass essential oil, without adding any extra components to the system, causing minimal thermal impact and reaching high quality for the essential oil extracted at the distillate stream. Experiments were carried out using a centrifugal molecular distillation unit with an evaporator temperature (EVT) from 60 to 120 °C and a feed flow rate (Q) from 1.5 to 4.5 mL 3 min1. Experimental protocols for oil and fat analysis were used to characterize the materials extracted. Results (obtained using GCMS) showed that bSPD was successful in the separation and purification of essential oil. High-quality essential oil was confirmed because of citral concentration increases from 19.816 mgcitral 3 mL1 (initial sample) to 40.963 mgcitral 3 mL1 (at 120 °C and 4.5 mL 3 min1), reaching a concentration of the bioactive compound (citral) in the distillate stream of 2.1 times the concentration in the original sample. The density, dynamic viscosity, and free fatty acids were 0.901 g 3 cm3, 2.069 mPa 3 s1, and 1.26 wt % (oleic acid), respectively, satisfying the oil quality criterion and avoiding thermal degradation.
’ INTRODUCTION Cymbopogon citratus (DC.) Stapf. (Gramineae), the scientific name of a plant also known worldwide as lemongrass, is a plant cultivated in almost all tropical and subtropical countries as a source of essential oil.1Lemongrasses are a group of commercially important C4 tropical grasses.2 The species name relates to the prominent lemon fragrance of that plant, which is due to its high concentration of citral and refers to the mixture of the isomeric acyclic monoterpene aldehydes, geranial and neral.3 Lemongrass is consumed as an aromatic drink, and it is also employed in medicine. Studies on extracts from lemongrass leaves have demonstrated anti-inflammatory, hypotensive, vasorelaxant, and diuretic activities.4 Lemongrass essential oil, acquired from Ferquima Ind. e Com. Ltda. (Vargem Grande Paulista, S~ao Paulo, Brazil) and used as a raw material in this work, is extracted by steam distillation of the fresh and dried leaves of lemongrass; the essential oil is yellow in color with a citrus/grass/lemon fragrance and its requirements were described in a accompanying technical report (Table 1). The chemical industry aims to efficiently manufacture products of high quality where the processing operations may vary from time to time. According to Marriott et al.5in the best possible separation performance, the quality of essential oils and formulations containing vegetable oils is very important and it involves analytical methods for the quantification and identification of the compounds and physicochemical analysis of both raw materials and products. In this sense, several authors have alluded to a possible relation to the presence of central nervous system activity in the essential oil of lemongrass6 and anticancer potential due to the high citral content.7 On the other hand, some authors presented assessment parameters for an acceptable essential oil r 2011 American Chemical Society
and eventual toxic effects on humans.811 Thus, lemongrass essential oil must present a specific gravity of
