Microwave dry distillation as an useful tool for extraction of edible essential oils

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1 The International Journal of Aromatherapy (2006) 16, The International Journal of Aromatherapy intl.elsevierhealth.com/journals/ijar Microwave dry distillation as an useful tool for extraction of edible essential oils N. Tigrine-Kordjani a, B.Y. Meklati b, *, F. Chemat c, * a Laboratoire d Analyse Organique Fonctionnelle, Faculté de Chimie, Université des Sciences et de la Technologie Houari Boumediene El Alia, BP 32, Bab Ezzouar, Alger, Algeria b Centre de Recherche Scientifique et Technique en Analyses Physico-Chimiques CRAPC, BP 248 Alger RP 16004, Alger, Algeria c UMR A 408 INRA Université d Avignon Sécurité et Qualité des Produits d Origine Végétale, 33, rue Louis Pasteur, Avignon cedex 1, France KEYWORDS Essential oil; Microwave; Extraction; Hydrodistillation; Food; Aromatherapy Summary Microwave Dry Distillation or microwave accelerated distillation (MAD) is proposed as a method for green extraction of edible essential oils extensively used in the fragrance, flavour, and pharmaceutical industries and also in aromatherapy. It is a combination of microwave heating and dry distillation, performed at atmospheric pressure without adding any solvent or water. Isolation and concentration of volatile compounds is performed by a single stage. Rosemary was extracted with MAD at atmospheric pressure and 100 C for 30 min. The extracted compounds were removed from the aqueous extract by simple decantation, determined by gas chromatography-flame ionisation (GC-FID) and identified by gas chromatography mass spectrometry (GC/MS). Hydrodistillation of rosemary was performed with 2 L of water for 3 h for comparison of the results with those provided by the proposed method: extraction time, yields, chemical composition and quality of the essential oil, efficiency and costs of the process. Extraction of essential oils from rosemary with MAD was better in terms of energy saving, extraction time (30 min versus 3 h), oxygenated fraction (59% versus 46%), exact product yield (0.6% versus 0.6%) and product quality. MAD is a green technology and appears as a good alternative for the extraction of edible essential oils from aromatic plants used in aromatherapy and the food industry. c 2006 Elsevier Ltd. All rights reserved. Introduction * Corresponding authors. Fax: (B.Y. Meklati). address: bmeklati@wissal.dz (B.Y. Meklati). The development of new separation techniques for the food industries has received a lot of attention lately due to the environmental restrictions, reducing waste water, and the need for minimizing the /$ - see front matter c 2006 Elsevier Ltd. All rights reserved. doi: /j.ijat

2 142 N. Tigrine-Kordjani et al. energy costs. There is also a constant demand to improve the quality of essential oils because consumers demand this quality in their food, pharmaceutical or perfumery products. Essential oils are complex mixtures of volatile substances generally present at low concentrations. Various different methods can be used for their extraction, e.g. hydrodistillation, steam distillation and cold pressing. The conventional methods for the extraction of the essential oils have some disadvantages. Losses of some volatile compounds, low extraction efficiency, degradation of unsaturated or ester compounds through thermal or hydrolytic effects and toxic solvent residue in the extract may be encountered using these extraction methods. For steam distillation and hydrodistillation, the elevated temperatures for long extraction periods can cause chemical modification of the oil components and often a loss of the most volatile molecules. When using solvent extraction, it is impossible to obtain a solvent-free product and this process usually results also in the loss of the highly volatile components. These shortcomings have led to the consideration of the use of new green techniques in essential oil extraction, which typically use less energy and avoid solvents, such as supercritical fluids (Reverchon, 1997). Microwave Dry Distillation or microwave accelerated distillation (MAD) is an original combination of microwave heating and dry distillation at atmospheric pressure. MAD was conceived for laboratory scale or industrial process applications in the extraction of essential oils from different kind of aromatic plants. Based on a relatively simple principle, this method involves placing fresh plant material in a microwave reactor, without any added solvent or water. The internal heating of the in situ water within the fresh plant material distends the plant cells and leads to rupture of the glands and oleiferous receptacles. This process thus frees essential oil, which is evaporated by the in situ water of the plant material. A cooling system outside the microwave oven condenses the distillate continuously. The excess of water is refluxed to the extraction vessel in order to restore the in situ water to the plant material. The MAD is neither a modified microwave assisted extraction (MAE) (Pare and Belanger, 1997), which uses organic solvents, nor a modified hydrodistillation (HD), which uses a large quantity of water. The aim of this research was to develop a method for the MAD extraction of rosemary essential oil, and compare the results with those obtained by hydrodistillation in terms of extraction time, yields, chemical composition and quality of the essential oil, and the environmentally friendly approach of the process. Rosemary (Rosmarinus officinalis L.) is an important herb on the world food and aromatherapy market. Natural antioxidants such as those present in rosemary essential oil may be an alternative source for compounds capable of protecting lipids in foods. Rosemary essential oil is also used as an antibacterial and antifungal agent. Experimental Plants material Rosemary (Rosmarinus officinalis L.) was collected in the north of Algeria. It was gathered from the same experimental plantation INA (Institut National Agronomique, Algiers, Algeria). Only fresh plant material was employed in all extractions. MAD apparatus and procedure MAD has been performed using the DryDist microwave oven illustrated in Fig. 1 (Chemat et al., 2004; Dry Dist, 2004). In a typical MAD procedure performed at atmospheric pressure, 200 g of fresh rosemary were heated using a fixed power of 200 W for 30 min without added any solvent or water. The extraction was continued at 100 C until no more essential oil was obtained. The essential oil was collected, dried under anhydrous sodium sulphate and stored at 4 C until used. The extractions were performed at least three times, and the mean values were reported. Hydrodistillation apparatus and procedure Two hundred grams of fresh rosemary were submitted to hydrodistillation with a Clevenger-type apparatus (Clevenger, 1928) according to the European Pharmacopoeia and extracted with 2 L of water for 3 h (until no more essential oil was obtained). The essential oil was collected, dried under anhydrous sodium sulphate and stored at 4 C until used. The extractions were performed at least three times, and the mean values were reported. Gas chromatography A Hewlett-Packard 6890 GC-FID system was used for gas chromatography analysis, fitted with a fused-silica-capillary column with an apolar stationary phase HP5MSä (30 m 0.25 mm 0.25 lm film thickness). The column temperature programme was 60 C for 8 min increased at 2 C/min

3 Microwave dry distillation as an useful tool for extraction of edible essential oils 143 Figure 1 Microwave Dry distillation system. to 250 C and held at 250 C for 15 min. Injection was performed at 250 C in the split-less mode; 1 ll of sample was injected. A flow rate of 0.3 ml/min carrier gas (N 2 ) was used. Flame ionisation detection was performed at 320 C. Analyses were performed at least three times, and the mean values were reported. Gas chromatography mass spectrometry identification The essential oils were analyzed by gas chromatography coupled to mass spectrometry (GC MS) (Hewlett-Packard computerised system comprising a 6890 gas chromatograph coupled to a 5973A mass spectrometer) using two fused-silica-capillary columns with different stationary phases. The non-polar column was HP5MSä (30 m 0.25 mm 0.25 lm film thickness) and the polar one was a Stabilwaxä consisting of Carbowaxä-PEG (60 m 0.2 mm 0.25 mm film thickness). GC MS spectra were obtained using the following conditions: carrier gas He; flow rate 0.3 ml/min; splitless mode; injection volume 1 ll; injection temperature 250 C; the oven temperature programme was 60 C for 8 min increased at 2 C/min to 250 C and held at 250 C for 15 min ; the ionisation mode used was electronic impact at 70 ev. Analyses were performed at least three times, and the mean values were reported. Qualitative and quantitative analyses Most constituents were tentatively identified by comparison of their GC Kovats retention indices (R.I.), determined with reference to an

4 144 N. Tigrine-Kordjani et al. Table 1 Qualitative and quantitative composition of rosemary essential oils obtained by MAD and HD Number Compound a R.I. b R.I. c MAD (%) d HD (%) d Method of identification Monoterpenes Bornylene GC-FID, GCMS 2 Tricyclene GC-FID, GCMS 3 Pinene ÆAlpha-æ GC-FID, GCMS 4 Camphene GC-FID, GCMS 5 Verbenene GC-FID, GCMS 6 sabinene GC-FID, GCMS 7 Pinene ÆBeta-æ GC-FID, GCMS 8 Myrcene ÆBeta-æ GC-FID, GCMS 9 I-phellandrene GC-FID, GCMS 10 Carene ÆDelta-3-æ GC-FID, GCMS 11 Terpinene ÆAlpha-æ GC-FID, GCMS 12 Cymene Æpara-æ GC-FID, GCMS 13 Limonene GC-FID, GCMS 14 Ocimene ÆBeta-æ GC-FID, GCMS 15 Ocimene Æcis-æ GC-FID, GCMS 16 Terpinene ÆGamma-æ GC-FID, GCMS 17 Terpinolene ÆAlpha-æ GC-FID, GCMS 18 Dehydro cymene Æpara-æ GC-FID, GCMS Oxygenated monoterpenes ,8-Cineole GC-FID, GCMS 20 Sabinene hydrate Æcis-æ GC-FID, GCMS 21 Linalool oxyde Æcis-æ GC-FID, GCMS 22 Camphenilone GC-FID, GCMS 23 Fenchone GC-FID, GCMS 24 Filifolone GC-FID, GCMS 25 Linalool GC-FID, GCMS 26 Hotrienol GC-FID, GCMS 27 Fenchyl alcohol GC-FID, GCMS 28 Chrysantenone GC-FID, GCMS 29 Campholenal ÆAlpha-æ GC-FID, GCMS 30 Camphor GC-FID, GCMS 31 Camphene hydrate GC-FID, GCMS 32 Pinocarvone GC-FID, GCMS 33 Borneol GC-FID, GCMS 34 Terpineol Æ4-æ GC-FID, GCMS 35 Campholenol ÆGamma-æ GC-FID, GCMS 36 Terpineol ÆAlpha-æ GC-FID, GCMS 37 Myrtenol GC-FID, GCMS 38 Verbenone GC-FID, GCMS 39 trans-carveol GC-FID, GCMS 40 Citronellol GC-FID, GCMS 41 Carvone GC-FID, GCMS 42 Carvotanacetone GC-FID, GCMS 43 Piperitone GC-FID, GCMS 44 Geraniol GC-FID, GCMS 45 3(10)-Carene-2-ol ÆE-æ GC-FID, GCMS 46 Isopiperitenone GC-FID, GCMS 47 Borneol acetate GC-FID, GCMS 48 Thymol GC-FID, GCMS 49 Carvacrol GC-FID, GCMS 50 Eucarvone GC-FID, GCMS 51 Verbanol acetate GC-FID, GCMS 52 Piperitenone GC-FID, GCMS 53 Eugenol GC-FID, GCMS 54 4-Methyl-2-(3-methyl-2-butenyl)-furane GC-FID, GCMS

5 Microwave dry distillation as an useful tool for extraction of edible essential oils 145 Table 1 (continued) Number Compound a R.I. b R.I. c MAD (%) d HD (%) d Method of identification 55 Methyl eugenol GC-FID, GCMS 56 Geranyl acetone GC-FID, GCMS Sesquiterpenes Caryophyllene Æiso-æ GC-FID, GCMS 58 Caryophyllene Ætrans-æ GC-FID, GCMS 59 Bergamotene ÆAlpha-trans-æ GC-FID, GCMS 60 Humulene ÆAlpha-æ GC-FID, GCMS 61 Farnesene ÆE-Beta-æ GC-FID, GCMS 62 Acoradiene ÆAlpha-æ GC-FID, GCMS 63 Curcumene ÆGamma-æ GC-FID, GCMS 64 Curcumene ÆAlpha-æ GC-FID, GCMS 65 Zingiberene GC-FID, GCMS 66 Bisabolene ÆAlpha-æ GC-FID, GCMS 67 Farnesene ÆAlpha-æ GC-FID, GCMS 68 Bisabolene ÆBeta-æ GC-FID, GCMS 69 Calamenene Æcis-æ GC-FID, GCMS 70 Sesquiphellandrene ÆBeta-æ GC-FID, GCMS 71 Bisabolene Ætrans-Gamma-æ GC-FID, GCMS Oxygenated sesquiterpenes Caryophyllene alcohol ÆAlpha-æ GC-FID, GCMS 73 Caryophyllene oxide GC-FID, GCMS 74 Humulene epoxide Æ1,2-æ GC-FID, GCMS 75 Bisabolene epoxide Æcis-Alpha-æ GC-FID, GCMS 76 Caryophylla-4(12),8(13) diene 5-ol ÆBeta-æ GC-FID, GCMS 77 Caryophylla-3(8)[13] diene 5-ol ÆBeta-æ GC-FID, GCMS 78 Sesquicyclogeraniol ÆBeta-æ GC-FID, GCMS 79 Bisabolol ÆAlpha-æ GC-FID, GCMS Diterpenes Isopimar-9(11)-15-diene GC-FID, GCMS 81 Dehydro abietan GC-FID, GCMS Other oxygenated compounds Octen-3 ol GC-FID, GCMS 83 3-Octanone GC-FID, GCMS 84 3,6-Octadienoic acid-3,7-dimethyl GC-FID, GCMS methyl ester 85 Undecanone GC-FID, GCMS 86 Damascenone ÆBeta-æ GC-FID, GCMS 87 Methyl-Jasmonate GC-FID, GCMS Extraction time (min) Yield (%) Total oxygenated compounds (%) Total non-oxygenated compounds (%) a Essential oil compounds sorted by chemical families. b Retention indices relative to C 5 C 28 n-alkanes calculated on non-polar HP5MSä capillary column. c Retention indices relative to C 5 C 28 n-alkanes calculated on polar Carbowaxä-PEG capillary column. d %: percentage calculated by GC-FID on non-polar HP5MSä capillary column. homologous series of C 5 C 28 n-alkanes and with those of authentic standards available in the authors laboratory. Identification was confirmed when possible by comparison of their mass spectral fragmentation patterns with those stored in the MS database (National Institute of Standards and Tech-

6 146 N. Tigrine-Kordjani et al. nology and Wiley libraries) and with mass spectra literature data (Adams, 1995). Component relative concentrations were obtained directly from GC peak areas. Results and discussion Extraction yield and time One of the advantages of the MAD method is rapidity. The extraction temperature is equal to the boiling point of water at atmospheric pressure (100 C) for both the MAD and HD extraction methods. To reach the extraction temperature (100 C) and thus obtain the first essential oil droplet, it is necessary to heat for only 2.5 min. with MAD compared with 30 min. for HD. As shown in Table 1, an extraction time of 30 min with SFME provides yields (0.57%) comparable to those obtained after 3 h by means of HD, which is one of the reference method in essential oil extraction. Composition of essential oil Substantially higher amounts of oxygenated compounds (59% versus 46%) and lower amounts of monoterpene hydrocarbons (34% versus 52%) are present in the essential oil of rosemary extracted by MAD in comparison with HD. Monoterpenes hydrocarbons are less valuable than oxygenated compounds in terms of their contribution to the fragrance of the essential oil. Conversely, the oxygenated compounds are highly odoriferous and, hence, the most valuable. The greater proportion of oxygenated compounds in the MAD essential oils is probably due to the diminution of thermal and hydrolytic effects, compared with hydrodistillation that uses a large quantity of water and is time and energy consuming. Water is a polar solvent, which accelerates many reactions, especially reactions via carbocation as intermediates. a-pinene, camphene, limonene, camphor, and verbenone were the main components in the essential oil extracted from rosemary but the relative amounts differed for the two extraction methods. a-pinene was the most abundant component. Verbenone, an oxygenated monoterpene, was present at 17.5% and 14.5%, respectively, for MAD and HD. Camphene, a monoterpene hydrocarbon, was present at 4.5% and 7.4%, respectively, for MAD and HD. Relatively few new compounds were found as a result of MAD extraction but these were present in very small amounts. The loss of some compounds in MAD compared with HD is probably not due to lack of their extraction but rather that the reduction in extraction time and the amount of water in the MAD method reduces the degradation of compounds by hydrolysis, trans-esterification or oxidation, and hence there are fewer degradation products noted in the analysis. Cost, energy, and environment ecology The reduced cost of extraction is clearly advantageous for the proposed MAD method in terms of time and energy. Hydrodistillation required an extraction time of 30 min for heating 2 L of water and 200 g of rosemary to the extraction temperature, followed by evaporation of water and essential oil for 150 min. The MAD method required heating for 3 min only and evaporation for 27 min of the in situ water and essential oil of rosemary. The energy required to perform the two extraction methods are, respectively, 4.33 kwh for HD, and 0.25 kwh for MAD. The power consumption was determined with a Wattmeter at the microwave generator entrance and the electrical heater power supply. Regarding environmental impact, the calculated quantity of carbon dioxide ejected in the atmosphere is higher in the case of HD (3464 g CO 2 /g of essential oil) than for MAD (200 g CO 2 /g of essential oil). These calculations have been made according to literature: to obtain 1 kwh from coal or fuel, 800 g of CO 2 will be rejected in the atmosphere during combustion of fossil fuel (Bernard, 2001). MAD is a very clean method, which avoids residue generation and the use of a large quantity of water and voluminous extraction vessels. MAD generates fresh aromatic herb without essential oil which could be used as food for ruminants. MAD eliminates wastewater treatment because no water is needed for the distillation. Conclusion The Microwave Dry Distillation or Microwave Accelerated Distillation (MAD) method offers important advantages over traditional hydrodistillation. It is quicker, more effective and has an environmentally friendly approach. These reasons make MAD a promising tool for the extraction of essential oils from aromatic and medicinal plants, of great concern in the food industry and aromatherapy.

7 Microwave dry distillation as an useful tool for extraction of edible essential oils 147 References Adams RP. Identification of essential oil components by gas chromatography/ mass spectroscopy. Carol Stream: Allured Publishing Corporation; Bernard. Sciences et vie 2001;214:68. Chemat F, Smadja J, Lucchesi ME. United Stated Patent, US ; Clevenger JF. American Perfumer and Essential Oil Review 1928:467. Dry Dist, Milestone srl, Via Fratebenefratelli, 1/5, I Sorisole, Bergamo, Italy, Available from: < com>. Pare JRJ, Belanger JMR. Instrumental methods in food analysis. Amsterdam: Elsevier Science; Reverchon E. J Supercrit Fluid 1997;10:1.