Microwave accelerated steam distillation of essential oil from lavender: A rapid, clean and environmentally friendly approach

Analytica Chimica Acta 555 (2006) 157–160

Microwave accelerated steam distillation of essential oil from lavender: A rapid, clean and environmentally friendly approach F. Chemat a,∗ , M.E. Lucchesi a , J. Smadja a , L. Favretto b , G. Colnaghi b , F. Visinoni b a

Laboratoire de Chimie des Substances Naturelles et des Sciences des Aliments, Facult´e des Sciences et Technologies, Universit´e de La R´eunion, B.P. 7151, 15 Avenue Rene Cassin, F-97715 Saint Denis Messag Cedex 9, La R´eunion, France b MILESTONE srl, Via Fratebenefratelli, 1/5, I-24010 Sorisole, Bergamo, Italy Received 8 April 2005; received in revised form 12 July 2005; accepted 22 August 2005 Available online 19 October 2005

Abstract A new process design and operation for microwave accelerated steam distillation (MASD) of essential oils was developed. A packed bed of lavender flowers (Lavandula angustifolia Mill., Lamiaceae) sits above the steam source generated by microwave heating. Only steam passes through it without the boiling water mixing with vegetable raw material, as is the case in hydro-distillation. MASD has been compared with a conventional technique, steam distillation (SD), for the extraction of essential oil from lavender flowers. Extraction of essential oils from lavender with MASD was better than SD in terms of energy saving, rapidity (10 min versus 90 min), product yield, cleanliness and product quality. © 2005 Elsevier B.V. All rights reserved. Keywords: Microwave; Steam distillation; Essential oil; Lavender flowers

1. Introduction Lavender is one of the most useful medicinal plants. Commercially, the lavender provides several important essential oils to the fragrance industry, including soaps, colognes, perfumes, skin lotions and other cosmetics. In food manufacturing, lavender essential oil is employed in flavouring beverages, ice cream, candy, baked goods and chewing gum. The essential oils of Lavandula species are obtained by steam distillation of the fresh flowering spikes. Oil quality is assessed by oil chemical composition and by the organoleptic opinion of the flavourists [1,2]. In general, an analytical procedure for essential oils or aromas from plants or spices comprises two steps: extraction (steam distillation, hydro-distillation, simultaneous distillation– extraction, . . .) and analysis (gas chromatography (GC), gas chromatography coupled to mass spectrometry (GC–MS)). Whereas the last step is finished after only 15–30 min, extraction takes at least several hours. It is frequently done by a prolonged heating and stirring in boiling water. Much more attention has been given to the application of microwave dielectric heating

∗

Corresponding author. Tel.: +262 262 938182; fax: +262 262 938183. E-mail address: [email protected] (F. Chemat).

0003-2670/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2005.08.071

in analytical chemistry because of the reducing analysis time, simplified manipulation and work-up, and higher purity of final product [3–5]. Up to now, however, there are only a few reports in the literature that mentioned the acceleration of essential oil extraction by microwave irradiation [6–10]. The aim of this work was to develop a new method, “microwave accelerated steam distillation”, for the extraction of essential oils, and compare the results with those obtained by conventional techniques, in order to introduce this advantageous alternative in the analytical or production of essential oils in food, cosmetic and pharmaceutical industry. To investigate the potential of MASD, comparisons have been made with conventional steam distillation for the extraction of essential oils from Lavandula angustifolia flowers. We intend to make appropriate comparison in term of extraction time, yield and aromatic composition. 2. Experimental 2.1. Plant material Lavender flowers (L. angustifolia Mill., Lamiaceae) were collected in June 2003 in Bergamo province (Northern Italy) and let dry on a bench in the shade.

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2.2. MASD apparatus and procedure Microwave accelerated steam distillation MASD has been performed in a Milestone ETHOS 1600 batch reactor [11]. It is a multimode microwave reactor operating at 2.45 GHz with a maximum delivered power of 1000 W variable in 10 W increments. The dimensions of the PTFE coated cavity are 35 cm × 35 cm × 35 cm. During experiments, time, temperature, pressure and power were controlled with the “easy-WAVE” software package. Temperature was monitored by a shielded thermocouple (ATC-300) inserted directly into the sample container and by an external infrared (IR) sensor. Temperature was controlled by a feedback to the microwave power regulator. A fix incident power of 500 W has been applied to the extraction medium. A wattmeter (W) has been added at the generator entrance, in order to measure the power consumption. A schematic diagram of the MASD apparatus used for essential oil extraction is shown in Fig. 1 The apparatus has a cylindrical Pyrex body (12 cm inside diameter and 12 cm long) with a Teflon grid at its lower end. A batch of 50 g of dry lavender flowers was packed in the MASD with 200 mL of water. The raw material forms the packed bed. At the bottom, steam is produced by heating water with microwave irradiation. Steam produced in the lower part of the apparatus passes through the lavender bed, evaporating and carrying the desired lavender essential oil, and is then directed towards the condenser, located on the top of the main apparatus body. Following condensation, the mixture

is decanted to separate oil and water. The excess of water was refluxed and recycled to the extraction vessel by cohobation in order to restore the water used for steam production. The essential oil is collected, dried with anhydrous sodium sulphate and stored at 4 ◦ C until used. Extractions were performed at least three times, and the mean values were reported. 2.3. Steam distillation apparatus and procedure For a rigorous comparison, the same glassware and same operating conditions have been used for conventional steam distillation. At the bottom of the steam producing section there is an electrical resistance heater whose power is controlled with a rheostat and used to heat and boil water. The essential oil is collected, dried with anhydrous sodium sulphate and stored at 4 ◦ C until used. A wattmeter (W) has been added at the generator entrance, in order to measure the power consumption. Extractions were performed at least three times, and the mean values were reported. 2.4. Gas chromatography–mass spectrometry identification The essential oils were analyzed by gas chromatography coupled to mass spectrometry (GC–MS) (HewlettPackard computerized system comprising a 5890 gas chromatograph coupled to a 5971A mass spectrometer) using a fused-silica-capillary column with an apolar stationary phase SBP5TM (60 m × 0.32 mm × 1 ␮m film thickness). GC–MS were obtained using the following conditions: carrier gas He; flow rate 0.7 mL min−1 ; split 1:20; injection volume 0.1 ␮L; injection temperature 250 ◦ C; oven temperature progress from 60 to 130 ◦ C at 1 ◦ C min−1 , from 130 to 200 ◦ C at 2 ◦ C min−1 , from 200 to 250 ◦ C at 4 ◦ C min−1 and holding at 250 ◦ C for 40 min; the ionisation mode used was electronic impact at 70 eV. Identification of the components was achieved from their relative retention indices on SBP5TM column, determined with reference to an homologous series of C8 –C22 n-alkanes, and by a comparison of their mass spectral fragmentation patterns with those stored in the data bank (Wiley/NBS library) and the literature [12,13]. Analyses were performed at least three times, and the mean values were reported. 3. Results and discussion

Fig. 1. Microwave accelerated steam distillation.

Microwave accelerated steam distillation (MASD) is an original combination of microwaves and steam distillation (SD). The apparatus is relatively simple. The isolation and concentration of essential oils are performed in a single stage. This process thus frees essential oil from plant material which is evaporated by steam. Once the essential oils have been extracted they can be analyzed directly by GC–MS without any preliminary clean-up or solvent exchange steps. Table 1 lists the yields, extraction time, grouped compounds and chemical composition of the essential oil from L. angustifolia flowers extracted by MASD and SD.

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Table 1 Yields, extraction times, grouped compounds and chemical compositions of essential oils obtained by MASD and SD from lavender flowers No.

Compounds

R.R.I.a

1 2 3 4 5 6 7 8 9 10 11 12

Monoterpenes ␣-Thujene ␣-Pinene Camphene Sabinene ␤-Pinene ␤-Myrcene
3-Carene Limonene (Z)-␤-Ocimene (E)-␤-Ocimene ␥-Terpinene Terpinolene

13 14 15 16 17 18 19 20

MASDb (%)

SDc (%)

907 914 933 963 968 985 1008 1024 1031 1040 1050 1078

3.54 0.08 0.51 0.32 0.14 0.59 0.50 0.22 tr. 0.33 0.37 0.09 0.37

4.92 tr. 0.90 0.52 0.18 0.82 0.85 0.29 tr. 0.41 0.53 0.00 0.40

Oxygenated monoterpenes 1,8-Cineole Sabinene hydrate-cis Linalool Camphor Borneol Terpin-4-ol p-Cymen-8-ol ␣-Terpineol

1027 1058 1099 1137 1161 1174 1179 1186

78.29 7.23 0.66 47.82 11.82 4.15 5.94 tr. 0.68

75.14 7.29 0.00 46.85 10.23 4.07 5.54 tr. 1.16

21 22 23 24 25

Sesquiterpenes ␣-Bergamotene cis ␤-Caryophyllene ␣-Santalene (E)-␤-Farnesene Sesquiterpene 1

1400 1412 1414 1453 1474

2.77 0.10 1.28 0.15 0.63 0.61

2.87 0.00 1.72 0.00 0.65 0.506

26 27

Oxygenated sesquiterpenes Caryophyllene oxide ␣-Bisabolol

1573 1677

0.29 0.11 0.18

1.08 0.19 0.89

28 29 30 31 32 33 34 35

Other oxygenated compounds Octan-3-one Octan-3-ol Dihydromyrcenol n.i. n.i. n.i. Linalool acetate Geranyl acetate

977 990 1063 1141 1188 1232 1254 1377

15.01 0.78 0.26 0.34 0.37 2.00 0.43 10.74 0.08

15.75 0.73 0.37 0.00 0.00 1.95 0.53 11.90 0.26

8.86 10 5

8.75 90 30

5

60

Fig. 2. Essential oil yields as a function of time for the MASD (䊉) and SD () extraction of lavender flowers.

temperature and thus obtain the distillation of the first essential oil droplet, it is necessary to heat only 5 min with MASD against 30 min for SD. As is shown in Table 1 and Fig. 2, an extraction time of 10 min with MASD provides yields comparable to those obtained after 90 min by means of SD, which is the one of the reference methods in essential oil extraction. The ultimate yield of essential oil obtained from L. angustifolia flowers was 8.86% by MASD and 8.75% by SD. These results mean a substantial saving of time, energy and plant material. 3.2. Composition of essential oil The essential oils of L. angustifolia flowers isolated either by MASD or SD are rather similar in their composition. The same number of volatile secondary metabolites is found in the essential oil isolated by MASD or SD, with similar yields. Linalool is the main oxygenated component in the essential oil extracted from lavender with equivalent relative amounts for both extraction methods. In this application, microwave irradiation highly accelerated the extraction process, but without causing considerable changes in the volatile oil composition, phenomenon which was already described by Pare and Belanger [14]. 3.3. Cost, energy and environment ecology

Yield (%) Total extraction time (min) Heating time from 20 to 100 ◦ C (min) Real extraction time (min)

tr., trace; n.i., non-identified. a R.R.I., relative retention indices relative to C –C TM 8 22 n-alkanes on SBP5 capillary column. b MASD, microwave accelerated steam distillation. c SD, steam distillation.

3.1. Extraction yield and time One of the advantages of the MASD is rapidity. For SD or MASD, the extraction temperature is equal to water boiling temperature at atmospheric pressure (100 ◦ C). To reach this

The reduced cost of extraction is clearly advantageous for the proposed MASD method in terms of time and energy. Steam distillation required an extraction time of 30 min for heating 200 g of water and 50 g of plant material to the extraction temperature, followed by evaporation of water and essential oil for 60 min. The MASD method required heating for 5 min only and evaporation for 5 min of the water and essential oil of the plant material. The energy required to perform the two extraction methods are, respectively, 1.5 kWh for SD, and 0.13 kWh for MASD. The power consumption has been determined with a wattmeter at the microwave generator entrance and the electrical heater power supply. Regarding environmental impact, the calculated quantity of carbon dioxide rejected in the atmosphere is higher in the case

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of SD (275 g CO2 /g of essential oil) than for MASD (25 g CO2 /g of essential oil). These calculations have been made according to literature [15]. To obtain 1 kWh from coal or fuel, 800 g of CO2 will be rejected in the atmosphere during combustion of fossil fuel. 4. Conclusion This is the first time that microwave has been used as heating source in a steam distillation device with good results concerning both extraction time and efficiency. Both the re-design of the glassware and the application of microwaves afford a development of a method that serves as an example of its usefulness. The advantages of the steam distillation (namely, continuous contact of the plant material with clean extractant “steam” and not solvent extraction required) remain in the new device MASD, which, in addition, is quicker and allows substantial saving in energy and costs. Acknowledgement The authors gratefully acknowledge le Conseil R´egional de La R´eunion (France D.O.M.) for financial support.

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