- Email: [email protected]
Valorization of solid wastes from essential oil industry
Journal of Food Engineering 104 (2011) 196–201
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Valorization of solid wastes from essential oil industry A. Navarrete a,⇑, M. Herrero b, A. Martín a, M.J. Cocero a, E. Ibáñez b a High Pressure Processes Group, Department of Chemical Engineering and Environmental Technology, University of Valladolid, Facultad de Ciencias, Prado de la Magdalena s/n, 47011 Valladolid, Spain b Institute of Food Science Research (CIAL-CSIC), Nicolás Cabrera 9, Campus UAM Cantoblanco, 28049 Madrid, Spain
a r t i c l e
i n f o
Article history: Received 30 April 2010 Received in revised form 5 October 2010 Accepted 7 October 2010 Available online 13 December 2010 Keywords: Antioxidants Carnosic acid Carnosol Rosmarinic acid Caffeic acid Chlorogenic acid Solvent extraction Valorization of residues Rosemary
a b s t r a c t Natural antioxidants have attracted attention owing to their potential good effects in health. On the other hand, valorization of residues is an opportunity to obtain profit in a sustainable way. In this work antioxidants were obtained from residues of rosemary after extraction of essential oil using steam distillation, hydrodistillation and Solvent Free Microwave Extraction (SFME). A solvent extraction with ethanol was used to obtain the antioxidants. Then a comparison of the results is made in order to know which process delivers a residue with higher concentration of antioxidants. Mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils. Higher yields and rates of extract from leaves after SFME have been observed. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Deterioration of fats and oils contained in food products is responsible of rancidity and reduced nutritional content in foodstuffs. The main cause of this process is lipid oxidation reaction (German, 2002). This reaction uses (mainly) the oxygen present in the air and can be catalyzed by light or certain metals and follows a free-radical chain reaction kinetics (Pokorny´, 1991). There have also been evidences pointing towards toxicity and other detrimental effects in human health related with this kind of reactions. To prevent this oxidation, antioxidants are used in the food industry, cosmetic products and some pharmaceutical products. They react with free radicals and, thus, interrupt the propagation step of these reactions. Some products including antioxidants in their formulations are fried foods, margarines containing animal fats, flakes, anti-ageing and photoprotection products. Recently, natural antioxidants have also attracted great attention owing to their potential health benefits reported, as well as due to the perception of possible hazardous effects related with synthetic antioxidants (Podsedek, 2007; Shahidi, 2000). Rosemary is a highly established medicinal plant and one of the main natural sources of antioxidants (see Table 1). The chemical structures of some of ⇑ Corresponding author. Tel.: +34 983 423 166. E-mail address: [email protected] (A. Navarrete). 0260-8774/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2010.10.033
the most important antioxidants found in rosemary are shown in Fig. 1. Growing interest is pointing towards natural antioxidants obtained using ‘‘green’’ processes. Natural antioxidants represented 38% of the market of antioxidants in 2004 (assuming a yearly growth of 6–7%) (Meyer et al., 2002). Thus, these products have a promising business perspective. Market tendency will probably be towards functional foods where antioxidants can play a major benefit for health (Pokorny´ and Korczak, 2001). Moreover, there is a new conscience about the limited resources available and the need to use, as efficiently as possible, raw materials and energy (European Commission, 2008; García-Serna et al., 2007; Jenck et al., 2004). The extraction of antioxidants from agricultural waste is thus an opportunity to obtain profit in a sustainable way from low-cost raw material. Works related to the antioxidants recovery from residues remaining after extraction have found positive results regarding their potential use in terms of content, market and suitability (Balasundram et al., 2006; Moure et al., 2001). Recently, there has been an increased research related to new technologies to extract natural compounds (Albu et al., 2004; Dai, 1999; Lucchesi et al., 2007; Pereira and Meireles, 2007; Riera et al., 2004; Starmans and Nijhuis, 1996; Wang and Weller, 2006). Particularly, the application of microwave energy has received attention owing to the reduction of time and energy required to obtain phytochemicals. Nevertheless, to our knowledge, at present there is not
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
197
Nomenclature Ci mextract msolution mplant
concentration of antioxidant i in the dried ethanolic extract (mg/mg extract) mass of dried ethanolic extract measured in the sample (mg) mass of solution sample (g) mass of dried plant fed to the system (g)
any published work focused on the use of residues from microwave extraction of essential oils. Therefore, the aim of this work was to evaluate the influence of a previous extraction of essential oil on the evolution of the extraction of antioxidants from rosemary, in order to study the possibility of obtaining antioxidants from rosemary essential oil residues. Three essential oil extraction techniques were used: steam distillation, hydrodistillation and Solvent Free Microwave Extraction (SFME). UPLC–ESI-MS/MS analysis of the extracts was carried out to obtain the concentrations of antioxidants in time. 2. Experimental 2.1. Plants and chemicals Rosemary used for essential oil extraction experiments was collected in September 2009, in Peñafiel (Valladolid, Spain). Plants were stored at 4 °C until needed for the extractions. For every experiment only the leaves and flowers were used, which were re-
Table 1 Antioxidants found in rosemary. Antioxidant
Techniques
mg/g dry plant References
Carnosol
SSE, SFE, PLE
0.15–41.7
Carnosic acid
EE, SSE SFE, PLE 2.0–20.4
Rosmarinic acid EE, SFE, PLE
3.3–4.0
Caffeic acid Chlorogenic acid Gallic acid
PLE PLE
0.14 0.04
Bicchi et al. (2000) and Herrero et al. (2010) Bicchi et al. (2000); Carvalho et al. (2005) and Herrero et al. (2010) Carvalho et al. (2005) and Herrero et al. (2010) Herrero et al. (2010) Herrero et al. (2010)
PLE
0.006
Herrero et al. (2010)
Ethanol Extraction (EE), Pressurized Liquid Extraction (PLE), Sonicated Solvent Extraction (SSE), Supercritical Fluid Extraction (SFE).
Fig. 1. Molecular structure of some antioxidants found in rosemary.
40 C qethanol
V
YExtract Yi
density of ethanol 96% at 40 °C (0.7840 g/ml) volume of the solution of ethanol used for the extraction (200 ml) yield of dried extract (mg/g_dried_plant) yield of antioxidant i (mg/g_dried_plant)
moved from the stems. Maximum storage time before use was 1 month. Ethanol (96%), which is regarded as a GRAS (generally recognized as safe) solvent to be used in the food industry, was used for the extraction of antioxidants (Panreac).
2.2. Steam distillation (SD) Fresh plant (100 g) was placed in a flask which was connected to a boiler. The steam was produced in the boiler by electrical heating (380 W) of distilled water. As the water started to boil, the vapor from the boiler went through the fresh plant. Then the vapor and the essential oil extracted from the plant passed through the cooler, where both the oil and water were condensed and collected (Fig. 2). The operation lasted 2 h.
2.3. Hydrodistillation (HD) Fresh plant (50 g) was placed in a flask containing 500 ml of distilled water and connected to a Clevenger distillation apparatus. Then electrical heating (380 W) was used. As the water started to boil, the vapor and the essential oil extracted from the plant passed through the cooler, where both the oil and water were condensed and collected as in steam distillation. The operation lasted 3 h.
2.4. Solvent Free Microwave Extraction (SFME) The extraction of essential oils using microwave energy was carried out in a modified microwave oven (Panasonic NN-GD 566 M). The oven was adapted to transport the steam out of the cavity. Hundred grams of fresh rosemary were introduced in the microwave oven and subjected to microwave heating at 1000 W. During the microwave heating, the sample rotates inside the cavity and, thanks to a rotary fitting; the steam can be removed continuously (Fig. 3). This setup allowed the samples to move through the uneven electromagnetic field pattern formed inside the oven, allowing for more uniform energy absorption. The operation was stopped after 5 min.
Fig. 2. Set up used in steam distillation extraction of essential oils.
198
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
2.5. Antioxidants extraction After each of the previous essential oil extraction methods (Sections 2.2–2.4) 50 g of the rosemary plants residues used for this extraction were weighted and preheated to 40 °C in a temperature controlled bath. Two hundred milliliters of ethanol were also measured and preheated to 40 °C. Then, rosemary and ethanol (96%) were put into contact in a 500 ml flask attached to a Rotavapor (Buchi, Switzerland, Flawil) and stirred in the bath at 40 °C at 5.5 rpm for 4 h. To follow the evolution of the extraction, samples of around 2 ml were taken at intervals along the 4 h. To do it, 0.2 lm-pore filters of nylon were used (Millex-GN). The resultant samples were then weighted and oven dried at 50 °C during 12 h and then new weight was registered. Single extractions were made from the plant residues. Therefore in order to estimate the overall error involved when extracting antioxidants after extraction of essential oils an independent study was made. Steam distillation which is the standard method to extract essential oils, was used as reference. For this study, three independent extractions of antioxidants were done as exposed above and the content of antioxidants followed each time. 2.6. UPLC–ESI-MS/MS analysis of the extracts Ultra Performance Liquid Chromatography tandem Electro Spray Ionization tandem Mass Spectrography (UPLC–ESI-MS/MS) analyses were carried out using an Accela (Thermo Scientific, San Jose, CA) liquid chromatograph equipped with a diode array detector (DAD) and an autosampler. The chromatograph was coupled to a TSQ Quantum (Thermo Scientific) triple quadrupole analyzer via an electrospray interface. The analytical conditions employed consisted of the use of a Hypersil Gold column (50 mm 2.1 mm, d.p. 1.9 lm) (Thermo Scientific) using as mobile phases acetonitrile (ACN) (0.1% formic acid, A) and water (0.1% formic acid, B) eluted according to the following gradient: 0 min, 95% B; 3.5 min, 50% B; 6.2 min, 5% B; 6.5 min; 5% B; 7 min, 95% B; 9 min, 95% B. The optimum flow rate was 0.4 mL/min while the injection volume was 5 lL. The diode array detector recorded the spectra from 200 to 450 nm. To quantify the antioxidants, the mass spectrometer was operated in the negative ESI multiple reaction monitoring (MRM) with a Q1 and Q3 resolution of 0.7 Da FWHM using scan width 0.010 Da and scan time of 0.040 s. The values corresponding to the tube lens voltage and collision energy were optimized for each quantified compound as indicated in Table 2. Preliminary LC–DAD–MS analyses were performed in order to identify the antioxidant compounds present in the extracts. The same Accela instrument and mobile phases were employed. An
Table 2 Optimized parameters of the MS detection of the phenolic compounds. Compound
Parent ion [MH]
Product ion [MH]
Collision energy (V)
Tube lens offset (V)
Carnosic acid Carnosol Rosmarinic acid p-Coumaric acid Caffeic acid Chlorogenic acid Gallic acid
331.3 329.3 359.2 163.1 179.1 353.2 169.1
287.197 285.078 161.026 119.193 135.166 191.047 125.204
28 20 20 19 17 21 18
88 73 78 75 66 78 66
analytical C18 column (150 4.6 mm, 3 lm d.p.) from Thermo was used, eluted at 400 ll/min according to the following stepwise gradient: 0 min, 95% B; 35 min, 60% B; 55 min; 5% B; 60 min, 5% B; 65 min, 95% B. 2.7. Moisture determination To use the yield on dry basis, moisture of the leaves should be known. Moisture content was calculated using the gravimetric method. A sample of approximately 100 g was weighted before and after 24 h oven-drying at 105 °C. The moisture reported was the water lost relative to the initial mass. 3. Results and discussion 3.1. Antioxidants quantification The calibration curve equations, concentration range used for each compound as well as the data regarding the performance of the quantification method (LODs and LOQs) are presented in Table 3. The concentration ranges used were selected according to the relative amounts of each compound found in the extracts. The linearity of these curves was always good, with R2 values higher than 0.99 for all the studied compounds. LOQs as low as 3.9 ng/ mL were reached. The reproducibility of the UPLC method was also good with RSD for the retention times lower than 3.2%. 3.2. Antioxidants extraction The yield of extract obtained with ethanol was calculated from the values measured in the samples extracted using Eq. (1) (Section 2.5). The density of the solution is assumed to be the same as the density of ethanol (96%) at 40 °C.
Y Extract ¼
Fig. 3. SFME setup used with rosemary leaves.
mextract 40 C V q msolution ethanol mplant
ð1Þ
As previously described, experimental error was estimated by repeating antioxidant extraction and analyses three times. The average standard deviation in the amount of extract measured in the control samples was 32.0 mg/g_dried_plant. Fig. 4a shows that higher extract yields were obtained for leaves processed using SFME, which produced twice as much extract than fresh plant. Thus, fresh plant would need much longer time to obtain the same amount of extract as in SFME. Changes in the structure of plants exposed to microwaves could explain this behavior (Al-Harahsheh and Kingman, 2004; Chemat et al., 2005; Lucchesi et al., 2007). After 3 h of boiling in hydrodistillation, it was possible to obtain extract from rosemary (187 mg/g_dried_plant), yielding around half of the extract obtained after SFME (343 mg/g_dried_plant). The yield after steam distillation was higher than those of fresh plants but lower than the yield obtained after SFME. Fig. 4b shows that all the final amounts of extract were achieved around 200 min
199
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
Table 3 Calibration curves and concentration ranges employed for the quantification. Limits of detection (LOD, S/N = 3) and limits of quantification (LOQ, S/N⁄ = 10) reached using the optimized UPLC–MS/MS method.
⁄
Compound
Tr (min) ± RSD (%)
Concentration range (lg/mL)
Calibration curve
R2
LOD (ng/mL)
LOQ (ng/mL)
Carnosic acid Carnosol Rosmarinic acid p-Coumaric acid Caffeic acid Chlorogenic acid Gallic acid
5.66 ± 0.2 5.16 ± 0.2 2.62 ± 0.8 2.17 ± 1.4 1.76 ± 2.4 1.53 ± 3.2 0.43 ± 2.0
0.098–25 0.098–100 0.098–25 0.098–6.25 0.098–25 0.098–25 0.098–6.25
y = 52915190x + 352,84,663 y = 6447799x + 196,79,405 y = 2380990x + 13,10,191 y = 1218043x + 314,172 y = 2841727x + 118,327 y = 2116742x + 275,272 y = 1664859x + 103,320
0.9959 0.9919 0.9959 0.9977 0.9998 0.9996 0.9999
1.18 5.99 5.12 123.20 21.41 13.96 33.84
3.93 19.97 17.07 410.66 71.37 46.53 112.79
S/N: Signal-to-Noise ratio.
Fig. 4. Evolution of dried extract. (a) Yield of dried extract. (b) Fraction of the total amount obtained. Solvent Free Microwave Extraction (SFME), steam distillation (SD), hydrodistillation (HD) and fresh plant (Fresh).
except for fresh plant. Thus, fresh plant would have more extract to deliver but it would require more time of extraction.
3.3. Evolution of antioxidants extraction The yield of antioxidants obtained was calculated by Eq. (2)
Y i ¼ Y Extract C i
ð2Þ
The maximum errors measured in the detection of the antioxidants are reported in Table 4. Carnosic acid, carnosol, rosmarinic acid, caffeic acid and chlorogenic acid, were detected in all the samples obtained during extraction. p-Coumaric acid was detected only in leaves subjected to SFME and during the first 90 min extraction in leaves subjected to steam distillation with accumulated yields of 5.5 103 and 4.3 104 mg/g_dried_plant, respectively (Table 5). Gallic acid was below its limit of quantification in extracts from all treatments. The amount of rosmarinic acid was below the range of values found in literature (Tables 1 and 5). Yield of carnosic acid obtained after SFME was in the range of values re-
Table 4 Maximum values of absolute and relative errors involved in the measurement of main antioxidants. Compound
Absolute error (mg/g dried plant)
Relative error (%)
Carnosic acid Carnosol Rosmarinic acid Caffeic acid Chlorogenic acid
1.7 104 8.3 102 1.2 102 9.2 104 3.7 104
5.03 1.25 1.50 0.94 0.95
ported but the other treatments delivered values much lower. The yields of the rest of antioxidants detected moved around the reported values. Antioxidants are known to be thermolabile substances; therefore it was expected to have negligible amounts after hydrodistillation. Nevertheless, steam distillation, hydrodistillation and SFME showed higher rates and yields of extraction (Fig. 5). Carnosol yield after SFME (30.57 mg/g_dried_plant) doubled those obtained after SD and HD. Yield of carnosic acid was around six times higher after SFME when compared with that of SD. Extraction of rosmarinic acid was faster in residues from SD and SFME. Similar results were observed for caffeic acid. To explain this behavior we should consider that, on the one hand thermal stresses during steam distillation and hydrodistillation can deform the microstructure of the leaves, but hydrophobic protective substances such as waxes would impede the loss of phenolic substances. On the other hand microwaves can break and even burst the internal structures in leaves, taking out just the essential oil. Thus, mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils owed to the physical changes produced in the plant structure (Cerpa et al., 2008; Chemat et al., 2006, 2005; Il et al., 2006; Spiro and Sau Soon, 1994). Furthermore, SFME lasts much less than the other extraction processes (ca. 5 min) thus the antioxidants present are preserved in higher extent. Chlorogenic acid yields were higher in rosemary after steam distillation, in addition, this compound showed high variability during the extraction. Another curious behavior was observed in carnosic acid extraction, its yield diminished with time after steam distillation and hydrodistillation. These findings should be studied in further works.
200
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
Table 5 Maximum yields of antioxidants, mg/g dried plant.
Fresh plant SD HD SFME
Rosmarinic acid
Carnosic acid
Carnosol
Caffeic acid
Chlorogenic acid
p-Coumaric acid
0.37 1.5 0.63 1.9
0.39 0.004 0.70 6.7
6.7 15 12 31
0.029 0.11 0.023 0.11
0.006 0.028 0.012 0.015
N.D N.D N.D 0.005
30 25 20 15 10 5 0
Rosmarinic acid mg/g dried plant
8 Carnosic acid mg/g dried plant
Carnosol mg/g dried plant
35
7 6 5 4 3 2 1 0
0
50
100
150 200 Time (min)
250
50
100
Chlorogenic acid mg/g dried plant
Caffeic acid mg/g dried plant
0.12 0.1 0.08 0.06 0.04 0.02 0 50
100
1.4 1.2 1 0.8 0.6 0.4 0.2
150
200
250
0
300
50
Time (min)
0.14
0
1.6
0 0
300
2 1.8
150 200 Time (min)
250
300
100
150 200 Time (min)
250
300
0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 0
50
100
150 200 Time (min)
250
300
Fig. 5. Evolution of the extraction of antioxidants of rosemary. Solvent Free Microwave Extraction (SFME), steam distillation (SD), hydrodistillation (HD) and fresh plant (Fresh).
4. Conclusions
References
In this work it has been shown that it is possible to extract antioxidants using a simple process (solvent extraction) from residual rosemary plants obtained after essential oil production. The content of antioxidants in residues of rosemary after extraction of essential oil with steam distillation, hydrodistillation and SFME was measured. The yields of antioxidants obtained after SFME are similar to those reported in literature. Mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils, indicating that the modification of the plant structure during these treatments effectively favours the antioxidants mass transfer. Higher yields and rates of extraction were obtained after SFME. Fresh plants and those extracted after HD yielded around half of the extract obtained after SFME. It was also confirmed the possibility of obtaining antioxidants after SD. Carnosol and carnosic acids increased noticeably their extraction rate and yield after the SFME process. Carnosol yield doubled those obtained after SD and HD; and was around six times higher for yields of carnosic acid.
Albu, S., Joyce, E., Paniwnyk, L., Lorimer, J.P., Mason, T.J., 2004. Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry. Ultrasonics Sonochemistry 11 (3–4), 261–265. Al-Harahsheh, M., Kingman, S.W., 2004. Microwave-assisted leaching – a review. Hydrometallurgy 73 (3–4), 189–203. Balasundram, N., Sundram, K., Samman, S., 2006. Phenolic compounds in plants and agri-industrial by-products: antioxidant activity, occurrence, and potential uses. Food Chemistry 99 (1), 191–203. Bicchi, C., Binello, A., Rubiolo, P., 2000. Determination of phenolic diterpene antioxidants in rosemary (Rosmarinus officinalis L.) with different methods of extraction and analysis. Phytochemical Analysis 11 (4), 236–242. Carvalho Jr., R.N., Moura, L.S., Rosa, P.T.V., Meireles, M.A.A., 2005. Supercritical fluid extraction from rosemary (Rosmarinus officinalis): Kinetic data, extract’s global yield, composition, and antioxidant activity. Journal of Supercritical Fluids 35 (3), 197–204. Cerpa, M.G., Mato, R.B., Cocero, M.J., 2008. Modeling steam distillation of essential oils: application to lavandin super oil. AIChE Journal 54 (4). Chemat, S., Aït-Amar, H., Lagha, A., Esveld, D.C., 2005. Microwave-assisted extraction kinetics of terpenes from caraway seeds. Chemical Engineering and Processing 44 (12), 1320–1326. Chemat, F., Lucchesi, M.E., Smadja, J., Favretto, L., Colnaghi, G., Visinoni, F., 2006. Microwave accelerated steam distillation of essential oil from lavender: a rapid, clean and environmentally friendly approach. Analytica Chimica Acta 555 (1), 157–160. Dai, J., 1999. Microwave-Assisted Extraction (M.A.E) of Neem and the Development of a Colorimetric Method for the Determination of Azadirachtin Related Limonoids. Mc. Gill University. European Commission, 2008. Novel Materials and Sustainable Chemistry – A Decade of EU-Funded Research. García-Serna, J., Pérez-Barrigón, L., Cocero, M.J., 2007. New trends for design towards sustainability in chemical engineering: green engineering. Chemical Engineering Journal 133 (1–3), 7–30.
Acknowledgements Funding provided by Junta Castilla y León (Spain), project GREX-11-2008 is gratefully acknowledged.
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201 German, J.B., 2002. Antioxidants. In: Branen, A.L., Davidson, P.M., Salminen, S., Thorngate, J.H. (Eds.), Food Additives, 2nd ed. Marcel Dekker, New York, pp. 523– 541. Herrero, M., Plaza, M., Cifuentes, A., Ibáñez, E., 2010. Green processes for the extraction of bioactives from Rosemary: Chemical and functional characterization via ultraperformance liquid chromatography-tandem mass spectrometry and in-vitro assays. Journal of Chromatography A 1217 (16), 2512–2520. Il, C., Seung Jun, C., Jae Keun, C., Tae Wha, M., 2006. Extraction yield of soluble protein and microstructure of soybean affected by microwave heating. Journal of Food Processing and Preservation 30 (4), 407–419. Jenck, J.F., Agterberg, F., Droescher, M.J., 2004. Products and processes for a sustainable chemical industry: a review of achievements and prospects. Green Chemistry 6 (11), 544–556. Lucchesi, M.E., Smadja, J., Bradshaw, S., Louw, W., Chemat, F., 2007. Solvent free microwave extraction of Elletaria cardamomum L.: a multivariate study of a new technique for the extraction of essential oil. Journal of Food Engineering 79 (3), 1079–1086. Meyer, A.S., Suhr, K.I., Nielsen, P., Lyngby, Holm, F., 2002. Natural food preservatives. In: Ohlsson, T., Bengtsson, N. (Eds.), Minimal Processing Technologies in the Food Industry. CRC Press, Boca Raton, pp. 124–174. Moure, A., Cruz, J.M., Franco, D., Domínguez, J.M., Sineiro, J., Domínguez, H., José Núñez, M., Parajó, J.C., 2001. Natural antioxidants from residual sources. Food Chemistry 72 (2), 145–171.
201
Pereira, C.G., Meireles, M.A.A., 2007. Economic analysis of rosemary, fennel and anise essential oils obtained by supercritical fluid extraction. Flavour and Fragrance Journal 22 (5), 407–413. Podsedek, A., 2007. Natural antioxidants and antioxidant capacity of Brassica vegetables: a review. LWT – Food Science and Technology 40 (1), 1–11. Pokorny´, J., 1991. Natural antioxidants for food use. Trends in Food Science and Technology 2, 223–227. Pokorny´, J., Korczak, J., 2001. Preparation of natural antioxidants. In: Pokorny´, J., Yanishlieva, N., Gordon, M. (Eds.), Antioxidants in Food: Practical Applications. CRC. Riera, E., Golás, Y., Blanco, A., Gallego, J.A., Blasco, M., Mulet, A., 2004. Mass transfer enhancement in supercritical fluids extraction by means of power ultrasound. Ultrasonics Sonochemistry 11 (3–4), 241–244. Shahidi, F., 2000. Antioxidants in food and food antioxidants. Nahrung/Food 44 (3), 158–163. Spiro, M., Sau Soon, C., 1994. Kinetics of solvent extraction of essential oil from rosemary leaves. Flavour and Fragrance Journal 9 (4), 187–200. Starmans, D.A.J., Nijhuis, H.H., 1996. Extraction of secondary metabolites from plant material: a review. Trends in Food Science and Technology 7 (6), 191– 197. Wang, L.J., Weller, C.L., 2006. Recent advances in extraction of nutraceuticals from plants. Trends in Food Science and Technology 17 (6), 300–312.
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Valorization of solid wastes from essential oil industry A. Navarrete a,⇑, M. Herrero b, A. Martín a, M.J. Cocero a, E. Ibáñez b a High Pressure Processes Group, Department of Chemical Engineering and Environmental Technology, University of Valladolid, Facultad de Ciencias, Prado de la Magdalena s/n, 47011 Valladolid, Spain b Institute of Food Science Research (CIAL-CSIC), Nicolás Cabrera 9, Campus UAM Cantoblanco, 28049 Madrid, Spain
a r t i c l e
i n f o
Article history: Received 30 April 2010 Received in revised form 5 October 2010 Accepted 7 October 2010 Available online 13 December 2010 Keywords: Antioxidants Carnosic acid Carnosol Rosmarinic acid Caffeic acid Chlorogenic acid Solvent extraction Valorization of residues Rosemary
a b s t r a c t Natural antioxidants have attracted attention owing to their potential good effects in health. On the other hand, valorization of residues is an opportunity to obtain profit in a sustainable way. In this work antioxidants were obtained from residues of rosemary after extraction of essential oil using steam distillation, hydrodistillation and Solvent Free Microwave Extraction (SFME). A solvent extraction with ethanol was used to obtain the antioxidants. Then a comparison of the results is made in order to know which process delivers a residue with higher concentration of antioxidants. Mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils. Higher yields and rates of extract from leaves after SFME have been observed. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Deterioration of fats and oils contained in food products is responsible of rancidity and reduced nutritional content in foodstuffs. The main cause of this process is lipid oxidation reaction (German, 2002). This reaction uses (mainly) the oxygen present in the air and can be catalyzed by light or certain metals and follows a free-radical chain reaction kinetics (Pokorny´, 1991). There have also been evidences pointing towards toxicity and other detrimental effects in human health related with this kind of reactions. To prevent this oxidation, antioxidants are used in the food industry, cosmetic products and some pharmaceutical products. They react with free radicals and, thus, interrupt the propagation step of these reactions. Some products including antioxidants in their formulations are fried foods, margarines containing animal fats, flakes, anti-ageing and photoprotection products. Recently, natural antioxidants have also attracted great attention owing to their potential health benefits reported, as well as due to the perception of possible hazardous effects related with synthetic antioxidants (Podsedek, 2007; Shahidi, 2000). Rosemary is a highly established medicinal plant and one of the main natural sources of antioxidants (see Table 1). The chemical structures of some of ⇑ Corresponding author. Tel.: +34 983 423 166. E-mail address: [email protected] (A. Navarrete). 0260-8774/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2010.10.033
the most important antioxidants found in rosemary are shown in Fig. 1. Growing interest is pointing towards natural antioxidants obtained using ‘‘green’’ processes. Natural antioxidants represented 38% of the market of antioxidants in 2004 (assuming a yearly growth of 6–7%) (Meyer et al., 2002). Thus, these products have a promising business perspective. Market tendency will probably be towards functional foods where antioxidants can play a major benefit for health (Pokorny´ and Korczak, 2001). Moreover, there is a new conscience about the limited resources available and the need to use, as efficiently as possible, raw materials and energy (European Commission, 2008; García-Serna et al., 2007; Jenck et al., 2004). The extraction of antioxidants from agricultural waste is thus an opportunity to obtain profit in a sustainable way from low-cost raw material. Works related to the antioxidants recovery from residues remaining after extraction have found positive results regarding their potential use in terms of content, market and suitability (Balasundram et al., 2006; Moure et al., 2001). Recently, there has been an increased research related to new technologies to extract natural compounds (Albu et al., 2004; Dai, 1999; Lucchesi et al., 2007; Pereira and Meireles, 2007; Riera et al., 2004; Starmans and Nijhuis, 1996; Wang and Weller, 2006). Particularly, the application of microwave energy has received attention owing to the reduction of time and energy required to obtain phytochemicals. Nevertheless, to our knowledge, at present there is not
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
197
Nomenclature Ci mextract msolution mplant
concentration of antioxidant i in the dried ethanolic extract (mg/mg extract) mass of dried ethanolic extract measured in the sample (mg) mass of solution sample (g) mass of dried plant fed to the system (g)
any published work focused on the use of residues from microwave extraction of essential oils. Therefore, the aim of this work was to evaluate the influence of a previous extraction of essential oil on the evolution of the extraction of antioxidants from rosemary, in order to study the possibility of obtaining antioxidants from rosemary essential oil residues. Three essential oil extraction techniques were used: steam distillation, hydrodistillation and Solvent Free Microwave Extraction (SFME). UPLC–ESI-MS/MS analysis of the extracts was carried out to obtain the concentrations of antioxidants in time. 2. Experimental 2.1. Plants and chemicals Rosemary used for essential oil extraction experiments was collected in September 2009, in Peñafiel (Valladolid, Spain). Plants were stored at 4 °C until needed for the extractions. For every experiment only the leaves and flowers were used, which were re-
Table 1 Antioxidants found in rosemary. Antioxidant
Techniques
mg/g dry plant References
Carnosol
SSE, SFE, PLE
0.15–41.7
Carnosic acid
EE, SSE SFE, PLE 2.0–20.4
Rosmarinic acid EE, SFE, PLE
3.3–4.0
Caffeic acid Chlorogenic acid Gallic acid
PLE PLE
0.14 0.04
Bicchi et al. (2000) and Herrero et al. (2010) Bicchi et al. (2000); Carvalho et al. (2005) and Herrero et al. (2010) Carvalho et al. (2005) and Herrero et al. (2010) Herrero et al. (2010) Herrero et al. (2010)
PLE
0.006
Herrero et al. (2010)
Ethanol Extraction (EE), Pressurized Liquid Extraction (PLE), Sonicated Solvent Extraction (SSE), Supercritical Fluid Extraction (SFE).
Fig. 1. Molecular structure of some antioxidants found in rosemary.
40 C qethanol
V
YExtract Yi
density of ethanol 96% at 40 °C (0.7840 g/ml) volume of the solution of ethanol used for the extraction (200 ml) yield of dried extract (mg/g_dried_plant) yield of antioxidant i (mg/g_dried_plant)
moved from the stems. Maximum storage time before use was 1 month. Ethanol (96%), which is regarded as a GRAS (generally recognized as safe) solvent to be used in the food industry, was used for the extraction of antioxidants (Panreac).
2.2. Steam distillation (SD) Fresh plant (100 g) was placed in a flask which was connected to a boiler. The steam was produced in the boiler by electrical heating (380 W) of distilled water. As the water started to boil, the vapor from the boiler went through the fresh plant. Then the vapor and the essential oil extracted from the plant passed through the cooler, where both the oil and water were condensed and collected (Fig. 2). The operation lasted 2 h.
2.3. Hydrodistillation (HD) Fresh plant (50 g) was placed in a flask containing 500 ml of distilled water and connected to a Clevenger distillation apparatus. Then electrical heating (380 W) was used. As the water started to boil, the vapor and the essential oil extracted from the plant passed through the cooler, where both the oil and water were condensed and collected as in steam distillation. The operation lasted 3 h.
2.4. Solvent Free Microwave Extraction (SFME) The extraction of essential oils using microwave energy was carried out in a modified microwave oven (Panasonic NN-GD 566 M). The oven was adapted to transport the steam out of the cavity. Hundred grams of fresh rosemary were introduced in the microwave oven and subjected to microwave heating at 1000 W. During the microwave heating, the sample rotates inside the cavity and, thanks to a rotary fitting; the steam can be removed continuously (Fig. 3). This setup allowed the samples to move through the uneven electromagnetic field pattern formed inside the oven, allowing for more uniform energy absorption. The operation was stopped after 5 min.
Fig. 2. Set up used in steam distillation extraction of essential oils.
198
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
2.5. Antioxidants extraction After each of the previous essential oil extraction methods (Sections 2.2–2.4) 50 g of the rosemary plants residues used for this extraction were weighted and preheated to 40 °C in a temperature controlled bath. Two hundred milliliters of ethanol were also measured and preheated to 40 °C. Then, rosemary and ethanol (96%) were put into contact in a 500 ml flask attached to a Rotavapor (Buchi, Switzerland, Flawil) and stirred in the bath at 40 °C at 5.5 rpm for 4 h. To follow the evolution of the extraction, samples of around 2 ml were taken at intervals along the 4 h. To do it, 0.2 lm-pore filters of nylon were used (Millex-GN). The resultant samples were then weighted and oven dried at 50 °C during 12 h and then new weight was registered. Single extractions were made from the plant residues. Therefore in order to estimate the overall error involved when extracting antioxidants after extraction of essential oils an independent study was made. Steam distillation which is the standard method to extract essential oils, was used as reference. For this study, three independent extractions of antioxidants were done as exposed above and the content of antioxidants followed each time. 2.6. UPLC–ESI-MS/MS analysis of the extracts Ultra Performance Liquid Chromatography tandem Electro Spray Ionization tandem Mass Spectrography (UPLC–ESI-MS/MS) analyses were carried out using an Accela (Thermo Scientific, San Jose, CA) liquid chromatograph equipped with a diode array detector (DAD) and an autosampler. The chromatograph was coupled to a TSQ Quantum (Thermo Scientific) triple quadrupole analyzer via an electrospray interface. The analytical conditions employed consisted of the use of a Hypersil Gold column (50 mm 2.1 mm, d.p. 1.9 lm) (Thermo Scientific) using as mobile phases acetonitrile (ACN) (0.1% formic acid, A) and water (0.1% formic acid, B) eluted according to the following gradient: 0 min, 95% B; 3.5 min, 50% B; 6.2 min, 5% B; 6.5 min; 5% B; 7 min, 95% B; 9 min, 95% B. The optimum flow rate was 0.4 mL/min while the injection volume was 5 lL. The diode array detector recorded the spectra from 200 to 450 nm. To quantify the antioxidants, the mass spectrometer was operated in the negative ESI multiple reaction monitoring (MRM) with a Q1 and Q3 resolution of 0.7 Da FWHM using scan width 0.010 Da and scan time of 0.040 s. The values corresponding to the tube lens voltage and collision energy were optimized for each quantified compound as indicated in Table 2. Preliminary LC–DAD–MS analyses were performed in order to identify the antioxidant compounds present in the extracts. The same Accela instrument and mobile phases were employed. An
Table 2 Optimized parameters of the MS detection of the phenolic compounds. Compound
Parent ion [MH]
Product ion [MH]
Collision energy (V)
Tube lens offset (V)
Carnosic acid Carnosol Rosmarinic acid p-Coumaric acid Caffeic acid Chlorogenic acid Gallic acid
331.3 329.3 359.2 163.1 179.1 353.2 169.1
287.197 285.078 161.026 119.193 135.166 191.047 125.204
28 20 20 19 17 21 18
88 73 78 75 66 78 66
analytical C18 column (150 4.6 mm, 3 lm d.p.) from Thermo was used, eluted at 400 ll/min according to the following stepwise gradient: 0 min, 95% B; 35 min, 60% B; 55 min; 5% B; 60 min, 5% B; 65 min, 95% B. 2.7. Moisture determination To use the yield on dry basis, moisture of the leaves should be known. Moisture content was calculated using the gravimetric method. A sample of approximately 100 g was weighted before and after 24 h oven-drying at 105 °C. The moisture reported was the water lost relative to the initial mass. 3. Results and discussion 3.1. Antioxidants quantification The calibration curve equations, concentration range used for each compound as well as the data regarding the performance of the quantification method (LODs and LOQs) are presented in Table 3. The concentration ranges used were selected according to the relative amounts of each compound found in the extracts. The linearity of these curves was always good, with R2 values higher than 0.99 for all the studied compounds. LOQs as low as 3.9 ng/ mL were reached. The reproducibility of the UPLC method was also good with RSD for the retention times lower than 3.2%. 3.2. Antioxidants extraction The yield of extract obtained with ethanol was calculated from the values measured in the samples extracted using Eq. (1) (Section 2.5). The density of the solution is assumed to be the same as the density of ethanol (96%) at 40 °C.
Y Extract ¼
Fig. 3. SFME setup used with rosemary leaves.
mextract 40 C V q msolution ethanol mplant
ð1Þ
As previously described, experimental error was estimated by repeating antioxidant extraction and analyses three times. The average standard deviation in the amount of extract measured in the control samples was 32.0 mg/g_dried_plant. Fig. 4a shows that higher extract yields were obtained for leaves processed using SFME, which produced twice as much extract than fresh plant. Thus, fresh plant would need much longer time to obtain the same amount of extract as in SFME. Changes in the structure of plants exposed to microwaves could explain this behavior (Al-Harahsheh and Kingman, 2004; Chemat et al., 2005; Lucchesi et al., 2007). After 3 h of boiling in hydrodistillation, it was possible to obtain extract from rosemary (187 mg/g_dried_plant), yielding around half of the extract obtained after SFME (343 mg/g_dried_plant). The yield after steam distillation was higher than those of fresh plants but lower than the yield obtained after SFME. Fig. 4b shows that all the final amounts of extract were achieved around 200 min
199
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
Table 3 Calibration curves and concentration ranges employed for the quantification. Limits of detection (LOD, S/N = 3) and limits of quantification (LOQ, S/N⁄ = 10) reached using the optimized UPLC–MS/MS method.
⁄
Compound
Tr (min) ± RSD (%)
Concentration range (lg/mL)
Calibration curve
R2
LOD (ng/mL)
LOQ (ng/mL)
Carnosic acid Carnosol Rosmarinic acid p-Coumaric acid Caffeic acid Chlorogenic acid Gallic acid
5.66 ± 0.2 5.16 ± 0.2 2.62 ± 0.8 2.17 ± 1.4 1.76 ± 2.4 1.53 ± 3.2 0.43 ± 2.0
0.098–25 0.098–100 0.098–25 0.098–6.25 0.098–25 0.098–25 0.098–6.25
y = 52915190x + 352,84,663 y = 6447799x + 196,79,405 y = 2380990x + 13,10,191 y = 1218043x + 314,172 y = 2841727x + 118,327 y = 2116742x + 275,272 y = 1664859x + 103,320
0.9959 0.9919 0.9959 0.9977 0.9998 0.9996 0.9999
1.18 5.99 5.12 123.20 21.41 13.96 33.84
3.93 19.97 17.07 410.66 71.37 46.53 112.79
S/N: Signal-to-Noise ratio.
Fig. 4. Evolution of dried extract. (a) Yield of dried extract. (b) Fraction of the total amount obtained. Solvent Free Microwave Extraction (SFME), steam distillation (SD), hydrodistillation (HD) and fresh plant (Fresh).
except for fresh plant. Thus, fresh plant would have more extract to deliver but it would require more time of extraction.
3.3. Evolution of antioxidants extraction The yield of antioxidants obtained was calculated by Eq. (2)
Y i ¼ Y Extract C i
ð2Þ
The maximum errors measured in the detection of the antioxidants are reported in Table 4. Carnosic acid, carnosol, rosmarinic acid, caffeic acid and chlorogenic acid, were detected in all the samples obtained during extraction. p-Coumaric acid was detected only in leaves subjected to SFME and during the first 90 min extraction in leaves subjected to steam distillation with accumulated yields of 5.5 103 and 4.3 104 mg/g_dried_plant, respectively (Table 5). Gallic acid was below its limit of quantification in extracts from all treatments. The amount of rosmarinic acid was below the range of values found in literature (Tables 1 and 5). Yield of carnosic acid obtained after SFME was in the range of values re-
Table 4 Maximum values of absolute and relative errors involved in the measurement of main antioxidants. Compound
Absolute error (mg/g dried plant)
Relative error (%)
Carnosic acid Carnosol Rosmarinic acid Caffeic acid Chlorogenic acid
1.7 104 8.3 102 1.2 102 9.2 104 3.7 104
5.03 1.25 1.50 0.94 0.95
ported but the other treatments delivered values much lower. The yields of the rest of antioxidants detected moved around the reported values. Antioxidants are known to be thermolabile substances; therefore it was expected to have negligible amounts after hydrodistillation. Nevertheless, steam distillation, hydrodistillation and SFME showed higher rates and yields of extraction (Fig. 5). Carnosol yield after SFME (30.57 mg/g_dried_plant) doubled those obtained after SD and HD. Yield of carnosic acid was around six times higher after SFME when compared with that of SD. Extraction of rosmarinic acid was faster in residues from SD and SFME. Similar results were observed for caffeic acid. To explain this behavior we should consider that, on the one hand thermal stresses during steam distillation and hydrodistillation can deform the microstructure of the leaves, but hydrophobic protective substances such as waxes would impede the loss of phenolic substances. On the other hand microwaves can break and even burst the internal structures in leaves, taking out just the essential oil. Thus, mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils owed to the physical changes produced in the plant structure (Cerpa et al., 2008; Chemat et al., 2006, 2005; Il et al., 2006; Spiro and Sau Soon, 1994). Furthermore, SFME lasts much less than the other extraction processes (ca. 5 min) thus the antioxidants present are preserved in higher extent. Chlorogenic acid yields were higher in rosemary after steam distillation, in addition, this compound showed high variability during the extraction. Another curious behavior was observed in carnosic acid extraction, its yield diminished with time after steam distillation and hydrodistillation. These findings should be studied in further works.
200
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201
Table 5 Maximum yields of antioxidants, mg/g dried plant.
Fresh plant SD HD SFME
Rosmarinic acid
Carnosic acid
Carnosol
Caffeic acid
Chlorogenic acid
p-Coumaric acid
0.37 1.5 0.63 1.9
0.39 0.004 0.70 6.7
6.7 15 12 31
0.029 0.11 0.023 0.11
0.006 0.028 0.012 0.015
N.D N.D N.D 0.005
30 25 20 15 10 5 0
Rosmarinic acid mg/g dried plant
8 Carnosic acid mg/g dried plant
Carnosol mg/g dried plant
35
7 6 5 4 3 2 1 0
0
50
100
150 200 Time (min)
250
50
100
Chlorogenic acid mg/g dried plant
Caffeic acid mg/g dried plant
0.12 0.1 0.08 0.06 0.04 0.02 0 50
100
1.4 1.2 1 0.8 0.6 0.4 0.2
150
200
250
0
300
50
Time (min)
0.14
0
1.6
0 0
300
2 1.8
150 200 Time (min)
250
300
100
150 200 Time (min)
250
300
0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 0
50
100
150 200 Time (min)
250
300
Fig. 5. Evolution of the extraction of antioxidants of rosemary. Solvent Free Microwave Extraction (SFME), steam distillation (SD), hydrodistillation (HD) and fresh plant (Fresh).
4. Conclusions
References
In this work it has been shown that it is possible to extract antioxidants using a simple process (solvent extraction) from residual rosemary plants obtained after essential oil production. The content of antioxidants in residues of rosemary after extraction of essential oil with steam distillation, hydrodistillation and SFME was measured. The yields of antioxidants obtained after SFME are similar to those reported in literature. Mass transfer rates of antioxidants from leaves are increased as a result of the previous extraction of essential oils, indicating that the modification of the plant structure during these treatments effectively favours the antioxidants mass transfer. Higher yields and rates of extraction were obtained after SFME. Fresh plants and those extracted after HD yielded around half of the extract obtained after SFME. It was also confirmed the possibility of obtaining antioxidants after SD. Carnosol and carnosic acids increased noticeably their extraction rate and yield after the SFME process. Carnosol yield doubled those obtained after SD and HD; and was around six times higher for yields of carnosic acid.
Albu, S., Joyce, E., Paniwnyk, L., Lorimer, J.P., Mason, T.J., 2004. Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry. Ultrasonics Sonochemistry 11 (3–4), 261–265. Al-Harahsheh, M., Kingman, S.W., 2004. Microwave-assisted leaching – a review. Hydrometallurgy 73 (3–4), 189–203. Balasundram, N., Sundram, K., Samman, S., 2006. Phenolic compounds in plants and agri-industrial by-products: antioxidant activity, occurrence, and potential uses. Food Chemistry 99 (1), 191–203. Bicchi, C., Binello, A., Rubiolo, P., 2000. Determination of phenolic diterpene antioxidants in rosemary (Rosmarinus officinalis L.) with different methods of extraction and analysis. Phytochemical Analysis 11 (4), 236–242. Carvalho Jr., R.N., Moura, L.S., Rosa, P.T.V., Meireles, M.A.A., 2005. Supercritical fluid extraction from rosemary (Rosmarinus officinalis): Kinetic data, extract’s global yield, composition, and antioxidant activity. Journal of Supercritical Fluids 35 (3), 197–204. Cerpa, M.G., Mato, R.B., Cocero, M.J., 2008. Modeling steam distillation of essential oils: application to lavandin super oil. AIChE Journal 54 (4). Chemat, S., Aït-Amar, H., Lagha, A., Esveld, D.C., 2005. Microwave-assisted extraction kinetics of terpenes from caraway seeds. Chemical Engineering and Processing 44 (12), 1320–1326. Chemat, F., Lucchesi, M.E., Smadja, J., Favretto, L., Colnaghi, G., Visinoni, F., 2006. Microwave accelerated steam distillation of essential oil from lavender: a rapid, clean and environmentally friendly approach. Analytica Chimica Acta 555 (1), 157–160. Dai, J., 1999. Microwave-Assisted Extraction (M.A.E) of Neem and the Development of a Colorimetric Method for the Determination of Azadirachtin Related Limonoids. Mc. Gill University. European Commission, 2008. Novel Materials and Sustainable Chemistry – A Decade of EU-Funded Research. García-Serna, J., Pérez-Barrigón, L., Cocero, M.J., 2007. New trends for design towards sustainability in chemical engineering: green engineering. Chemical Engineering Journal 133 (1–3), 7–30.
Acknowledgements Funding provided by Junta Castilla y León (Spain), project GREX-11-2008 is gratefully acknowledged.
A. Navarrete et al. / Journal of Food Engineering 104 (2011) 196–201 German, J.B., 2002. Antioxidants. In: Branen, A.L., Davidson, P.M., Salminen, S., Thorngate, J.H. (Eds.), Food Additives, 2nd ed. Marcel Dekker, New York, pp. 523– 541. Herrero, M., Plaza, M., Cifuentes, A., Ibáñez, E., 2010. Green processes for the extraction of bioactives from Rosemary: Chemical and functional characterization via ultraperformance liquid chromatography-tandem mass spectrometry and in-vitro assays. Journal of Chromatography A 1217 (16), 2512–2520. Il, C., Seung Jun, C., Jae Keun, C., Tae Wha, M., 2006. Extraction yield of soluble protein and microstructure of soybean affected by microwave heating. Journal of Food Processing and Preservation 30 (4), 407–419. Jenck, J.F., Agterberg, F., Droescher, M.J., 2004. Products and processes for a sustainable chemical industry: a review of achievements and prospects. Green Chemistry 6 (11), 544–556. Lucchesi, M.E., Smadja, J., Bradshaw, S., Louw, W., Chemat, F., 2007. Solvent free microwave extraction of Elletaria cardamomum L.: a multivariate study of a new technique for the extraction of essential oil. Journal of Food Engineering 79 (3), 1079–1086. Meyer, A.S., Suhr, K.I., Nielsen, P., Lyngby, Holm, F., 2002. Natural food preservatives. In: Ohlsson, T., Bengtsson, N. (Eds.), Minimal Processing Technologies in the Food Industry. CRC Press, Boca Raton, pp. 124–174. Moure, A., Cruz, J.M., Franco, D., Domínguez, J.M., Sineiro, J., Domínguez, H., José Núñez, M., Parajó, J.C., 2001. Natural antioxidants from residual sources. Food Chemistry 72 (2), 145–171.
201
Pereira, C.G., Meireles, M.A.A., 2007. Economic analysis of rosemary, fennel and anise essential oils obtained by supercritical fluid extraction. Flavour and Fragrance Journal 22 (5), 407–413. Podsedek, A., 2007. Natural antioxidants and antioxidant capacity of Brassica vegetables: a review. LWT – Food Science and Technology 40 (1), 1–11. Pokorny´, J., 1991. Natural antioxidants for food use. Trends in Food Science and Technology 2, 223–227. Pokorny´, J., Korczak, J., 2001. Preparation of natural antioxidants. In: Pokorny´, J., Yanishlieva, N., Gordon, M. (Eds.), Antioxidants in Food: Practical Applications. CRC. Riera, E., Golás, Y., Blanco, A., Gallego, J.A., Blasco, M., Mulet, A., 2004. Mass transfer enhancement in supercritical fluids extraction by means of power ultrasound. Ultrasonics Sonochemistry 11 (3–4), 241–244. Shahidi, F., 2000. Antioxidants in food and food antioxidants. Nahrung/Food 44 (3), 158–163. Spiro, M., Sau Soon, C., 1994. Kinetics of solvent extraction of essential oil from rosemary leaves. Flavour and Fragrance Journal 9 (4), 187–200. Starmans, D.A.J., Nijhuis, H.H., 1996. Extraction of secondary metabolites from plant material: a review. Trends in Food Science and Technology 7 (6), 191– 197. Wang, L.J., Weller, C.L., 2006. Recent advances in extraction of nutraceuticals from plants. Trends in Food Science and Technology 17 (6), 300–312.