ARTICLE pubs.acs.org/IECR
Extraction of Dill Seed Oil (Anethum sowa) Using Supercritical Carbon Dioxide and Comparison with Hydrodistillation O. P. Nautiyal*,†,‡ and K. K. Tiwari† † ‡
Institute of Chemical Technology, Department of Chemical Engineering, N. M. Parekh Marg, Matunga (E) Mumbai 400019, India Department of Chemistry, Lovely Professional University, Chaheru, Punjab, Phagwara 144402, India ABSTRACT: Dill seed oil contains constituents that work as carminative and find extensive use in the pharmaceuticals, food, flavors, cosmetics, and medical industries. The present study was thus carried out to investigate supercritical carbon dioxide (SC-CO2) process technology for the extraction of dill seed oil (Anethum sowa). The effects of pressure, temperature, flow rate, and batch time of SC-CO2 were optimized. The best results for dill oil extraction were obtained at of 35 °C, 25 MPa, and a density of 0.88 g/cm3. The dill oil obtained by SC-CO2 was obtained in good yield and a short batch process time. The major constituents extracted by SC-CO2 were limonene, 27.93%; carvone, 9.76%; dihydrocarvone, 26.74%; and dillapiole, 34.05%. The yield of oil was 5 wt %.
1. INTRODUCTION Dill seed oil over the years has been produced using various conventional techniques. Dill seed oil finds extensive applications in the field of medicine. It is a very important part of the formulation for gripe water as a carminative for infants. Hydrodistillation (or steam distillation) gives much lower yields and also sometimes causes burning of major constituents because of the high temperature of processing. Emphasis on improving dill oil yield and quality is crucial. We mainly wanted to investigate dill oil yield by investigating the supercritical carbon dioxide (SCCO2) technology and comparing its results with those for hydrodistillation. Because SC-CO2 is nontoxic under supercritical conditions as a solvent, it leaves no harmful residues. Food materials produced with supercritical fluid extraction (SFE) have been shown to be of high quality, often with superior properties not obtainable with other separation techniques.1,2 On the other hand, the dual issues of increased government regulation and higher energy costs create a negative environment for growth. Solvent extraction and separation of solvent by distillation are common process operations in the production of natural flavors and fragrances and both are influenced to some extent by the previously mentioned issues. We have optimized the process conditions of extraction utilizing SFE and hydrodistillation. After extraction, the dill oil was thoroughly examined for its quality by determination of its constituents with gas chromatography. The particle size of the grounded dill seed was also considered to play an important role, as fine powder allows air channelling to take place by both SFE and conventional techniques. Air channelling reduces the efficiency of the extraction process and reduces the yield. Coloring compounds are required to be present in extracted oil, but the dill oil recovered using conventional techniques is usually colorless. Hence, investigation of the SC-CO2 process for extracting dill oil was considered. The yield of oil ranges from 0.29% to 1.50%, depending on the conditions of the plant material, its maturity, height, and state of dryness. The drier and more mature the herb, the more time required for distillation. However, the yield of oil increases with the state of dryness, but only up to a certain point because dry r 2011 American Chemical Society
herb material containing an abundance of fully ripened seed is difficult to distill. The dried residue left after the distillation of the essential oils from the seeds of Anethum sowa contains 16.8% fats and 15.1% proteins, and therefore, it can be used as cattle feed.3,4
2. MATERIALS AND METHODS 2.1. SC-CO2 Extraction. Carbon dioxide gas (99.9%) was purchased from Indian Oxygen Limited. Anethum sowa seeds were purchased from the Mumbai suburb of India. The standards were purchased from Sigma-Aldrich Co. (St. Louis, MO). The SC-CO2 pilot plant (Figure1), with extractor and separator capacities of 1 L each, was imported from Uhde GmbH (Dortmund, Germany). The SC-CO2 pilot plant was procured with a grant from DST (Government of India). The moisture content of the seeds was determined with a Dein-Stark apparatus. The seeds were ground and sieved through an ASTM mesh of 60100 μm. For each experiment, 300 g of dill seed powder was charged into the extractor of the SFE plant as a uniform bed without any air channelling. Experiments were performed in triplicate. Experimental batches were analyzed intermittently using gas chromatography to determine the extraction of dill oil constituents. Extracted oil collected in the separator was recovered by depressurizing the supercritical CO2. The oil was analyzed on a Perkin-Elmer 8500 gas chromatograph using the following conditions: SE 30 column (10% on chromosorb W); 4 m 1/8 in. diameter; temperatures of injector and flame ionization detector, 300 and 300 °C, respectively; total flow rate of N2, 20 mL/min; and temperature program, initially 100 °C, raised to 280 °C at 10 °C/min. 2.2. Hydrodistillation. For each trial, 100 g of ground dill seed (dry weight) as mentioned earlier was charged into a Clevenger apparatus along with 500 mL of deionized water. The apparatus Received: September 15, 2010 Accepted: March 12, 2011 Revised: March 12, 2011 Published: March 28, 2011 5723
dx.doi.org/10.1021/ie101852u | Ind. Eng. Chem. Res. 2011, 50, 5723–5726
Industrial & Engineering Chemistry Research
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Figure 1. Schematic flow diagram of SC-CO2 pilot plant.
Table 1. Effect of Batch Time on Extraction of Dill Seed Oil and Its Major Constituentsa composition (%) batch time
mass of CO2
yield
(h)
(kg)
(%)
limonene
DHCb
carvone
DAc
1
5
2.49
34.85
5.08
38.13
21.25
2
10
2.93
29.58
5.06
39.33
23.10
3 4
15 20
3.65 3.80
31.93 32.48
5.02 5.02
39.36 38.72
23.15 22.10
5
25
4.02
29.42
5.20
40.24
24.25
Extraction temperature, 35 °C; extraction pressure, 20 MPa; flow rate of CO2, 5 kg/h; ground dill seed charged, 300 g. b Dihydrocarvone. c Dillapiole. a
was placed in a heating mantle and heated to distill the oil in the graduated Florentine tube. The process was carried out until no more oil was recovered. The oil was separated and analyzed by gas chromatography (GC).
3. RESULTS AND DISCUSSION 3.1. Effect of Batch Time on the Yield and Composition of Dill Seed Oil. The study was carried out employing the process
conditions of 15 h batch time, 20 MPa, 35 °C, and 5 kg/h flow rate of carbon dioxide. The yield was observed to increase with increasing batch time. The aroma of the extract resembled that of freshly crushed dill seeds. The mass composition of the major constituents of the oil was as follows: limonene [1-methyl-4-(1-methylethenyl)-cyclohexene], 32.48%; dihydrocarvone (2-methyl-5-prop-1-en-2-ylcyclohexan-1one), 5.02%; carvone [2-methyl-5-(1-methylethenyl)-2-cyclohexenone], 38.72%; and dillapiole (1-allyl-2,3-dimethoxy-4,
Figure 2. Effect of mass on yield of dill oil at 35 °C.
5-methylenedioxy benzene), 22.63%. Extraction of the major constituents, such as dihydrocarvone and carvone, remained practically unchanged. The contents of dihydrocarvone and carvone were 5 and 39 wt %, respectively, in the extract. When the batch time was increased, it was found that the D-limonene, carvone, dillapiole, and diydrocarvone contents also increased (Table 1). 3.2. Effect of Pressure on the Yield and Composition of Dill Seed Oil. The extraction was carried out by varying the pressure; with increasing pressure, the density of SC-CO2 was found to change from 0.58 to 0.91 g/cm3. As a result, the yield of dill oil also increased up to a pressure of 25 MPa, but decreased thereafter. Studies were thus conducted with pressures of 1030 MPa 5724
dx.doi.org/10.1021/ie101852u |Ind. Eng. Chem. Res. 2011, 50, 5723–5726
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Table 2. Effect of Pressure on Extraction of Dill Seed Oila pressure
mass of SC-CO2
density
yield
water content
(MPa)
(kg)
(g/cm3)
(%)
(%)
10
5
0.58
1.40
1.40
15
10
0.72
2.38
2.49
20
15
0.83
4.11
2.42
25
20
0.87
4.02
1.56
30
25
0.91
1.89
0.57
Extraction temperature, 40 °C; flow rate of CO2, 5 kg/h; batch time, 5 h; ground dill seed charged, 300 g. a
Table 3. Effect of Pressure on the Extraction of Dill Seed Oila
Figure 3. Effect of mass on extraction of dill oil at 40 °C.
pressure
mass of SC-CO2
density
yield
water content
(MPa)
(kg)
(g/cm3)
(%)
(%)
10
5
0.49
2.09
1.44
15
10
0.65
3.15
2.24
20
15
0.80
4.26
2.47
25
20
0.85
4.54
1.75
27.5
25
0.88
4.00
1.30
30
30
0.89
2.78
1.05
Extraction temperature, 45 °C; flow rate of CO2, 5 kg/h; batch time, 5 h; ground dill seed charged, 300 g. a
Figure 4. Effect of mass on extraction of dill oil at 45 °C.
and temperatures of 35, 40, and 45 °C (Figures 24). The yield of the oil ranged from 3.4% at 10 MPa to 5% at 25 MPa (Figure 4). Extraction with water and the extractions at 40 and 35 °C are presented in Tables 24. The yield of oil was found to increase with pressure up to 20 to 25 MPa and decreased with further increase in pressure. In all cases, it was seen that the yield of oil increased with increasing pressure up to some maximum value at an intermediate pressure. It can be pointed that the data at 35 °C were collected for dill seed from a different source and those at 40 and 45 °C were for the locally purchased material. Because biomaterials from different sources have different characteristics, their extraction characteristics were expected to be different. The solubility of any solute (dill seed oil) is a function of pressure and temperature. An increase in pressure leads to an increase in solvent density, which, in turn, causes an increase in solubility. However, the effect of temperature on solubility is complex. An increase in temperature reduces the density of solvent, thus
reducing the solubility. Simultaneously, an increase in temperature causes the solute vapor pressure to increase, thereby increasing solubility.5 To obtain a clear understanding of this complex behavior, the yield of dill seed oil was plotted as a function of the density of CO2. The data for the density of CO2 at various conditions of temperature and pressure are presented in Tables 1 and 3. It was found that dill seed from a different source, when extracted at 35 °C, gave an increased yield of oil when the density of CO2 increased. Because the seed was from a different source, comparison of the yield of oil was not made with that of the seed used for extraction at 40 and 45 °C. The extraction of dill seed at 40 and 45 °C showed that, at a constant density, as the temperature was increased, the yield of oil increased. However, anomalous behavior was seen after a density of about 0.8 g/cm3, which corresponds to a pressure of 20 MPa or above. It was observed that, when extraction at higher pressure was performed, there was a significant change in the bed height of the dill seed. At higher pressures, the bed height of the ground dill seed was much less than that of the fresh ground seed charged to the extractor. It was expected that a dense packing of the bed would provide a lower surface area for extraction. A very dense packing also causes channelling, which further reduces the yield of oil.6,7 The effect of pressure on the extraction of dill oil and water is presented in Figures 3 and 4. It was seen that water was extracted up to a content of 2.5%, when samples were withdrawn at different intervals of time during the 5-h batch time of extraction; it was found that water was being extracted during the entire period of extraction. From 6% moisture content of the seed charged for extraction, up to 2.5% of the water was extracted at pressures between 20 and 25 MPa. Extraction of dill seed oil with SC-CO2 yielded 5.00 wt %; with ethyl alcohol, 2.52 wt %; with hexane, 3.22 wt %; and by hydrodistillation, 3.20 wt % (Table 4). Dill oil was stored under refrigerator 5725
dx.doi.org/10.1021/ie101852u |Ind. Eng. Chem. Res. 2011, 50, 5723–5726
Industrial & Engineering Chemistry Research
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Table 4. Comparison of Extracts of Dill Seed Oil Obtained by Different Processes composition of volatile oil (%) process of extraction
a
oleoresin extracted (wt % of seed)
limonene
carvone
DHCa
DAb
SCF extraction, 35 °C, 25 MPa, 5 h
5.00
27.93
9.76
26.74
34.05
solvent extraction, ethyl alcohol, 12 h
11.32
2.52
6.11
3.92
57.29
28.34
solvent extraction, hexane, 12 h hydrodistillation, 12 h
5.24
3.22 3.20
1.23 35.12
7.01 12.85
51.20 31.61
35.86 19.00
Dihydrocarvone. b Dillapiole.
seed oil were determined to be 25 MPa at 35 °C. SCF-extracted oils are preferred over oils obtained from conventional techniques with regard to stringent regulation policies in the pharmaceutical, food, flavor, and pharmaceutical industries. The major constituents of the dill seed oil were best extracted by SCF extraction technology. Specifically, the major constituents of dill seed oil that determine the price of the essential oil were extracted with the best yield. The best conditions for dill oil extraction were a batch time of 3 h at 20 MPa and 35 °C.
Figure 5. Major constituents of dill oil.
Table 5. Physical Properties of Dill Seed Oila technique used
a
volatile oil (wt % of seed)
’ AUTHOR INFORMATION
density of oil
optical rotation
refractive index
(g/cm3)
[R]d28
[n]d32 0
SC-CO2
0.925
þ32°32
1.4915
hydrodistillation
0.872
þ32°320
1.4935
hexane
0.870
þ21°260
1.5070
Determinations of measure as per Guenther, E.
conditions for a year. After a year, no major changes were observed upon analysis of the oil by GC. It was observed that the chemical compositions of dill oil extracted by SCF at various pressures and temperatures were found to be in good yield and a few were found to be low. As the temperature was increased under supercritical conditions, because of a reduction in solvent density, some of the constituents were found to have been extracted in lower yield. For comparison, oil extracted using conventional techniques was also examined for its physical properties (Table 5).8,9
4. ANALYSIS AND ANALYTICAL METHODS Dill seed oil was intermittently analyzed by GC to study the progress of the extraction and the percent composition for its quality and flavor. The major constituents in the dill seed oil were limonene, carvone, dihydrocarvone, and dillapiole. The response factor of each component was considered to be unity. Analysis was done qualitatively, and hence no internal standard was used. Figure 5 shows the chemical structures of D-limonene, carvone, dihydrocarvone, and dillapiole. 5. CONCLUSIONS It was concluded that the process time, quality, yields of oil and constituents, flavor, and aroma of the oil obtained from SCF were pronounced, and that the recovered sample contained the fresh aroma of that of the pulverized seeds. The refractive index of the oil was superior to that of the oil obtained by conventional techniques. The best and optimized conditions for extracting dill
Corresponding Author
*Email:
[email protected],
[email protected].
’ ACKNOWLEDGMENT O.P.N. is very thankful and grateful to his mentor Ret. Professor K. K. Tiwari, Professor of Chemical Engineering, Chemical Engineering Division, ICT, Mumbai, India, and currently Visiting Professor at JUET, for his untiring guidance and moral support for his Ph.D. He provided a financial assistantship out of his consultancy and helped me to complete my doctorate. ’ REFERENCES (1) Paulaitis, M., Penninger, J., Gray, R., Davidson, P. Chemical Engineering at Supercritical Fluid Conditions; King, M, Alderson, D., Fallah, F., Kassim, K., Sheldon, J., Mahmud, R., Eds.; The Butterworth Group Publishers: Ann Arbor, MI, 1983. (2) Krukonis, V. J. Supercritical Fluid Extraction in Flavor Applications. In Characterization and Measurement of Flavor Compounds; Bills, D. D., Mussinan, C. J., Eds.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985; Vol. 289, Chapter 11, pp 154175. (3) Lack, E.; Simandi, B. Supercritical Fluid Extraction and Fractionation from Solid Materials. Ind. Chem. Lib. 2001, 9, 537–575. (4) Merkle, J. A.; Larick, D. K. Conditions for Extraction and Concentration of Beef Fat Volatiles with Supercritical Carbon Dioxide. J. Food Sci. 1994, 59 (3), 478–483. (5) Mishra, R. R. Studies in Extraction Using Supercritical Carbon Dioxide. Ph.D. Dissertation, Institute of Chemical Technology, Mumbai, India, 1991. (6) Sriniwas, S. R. Patchouli Oil. In Atlas of Essential Oils; Sriniwas, S. R., Ed.; Allured Publishing Corporation: New York, 1986; p 75. (7) Helen, Su C. F.; Robert, H. Investigation of the main components in insect-active dill seed extract. J. Agric. Food Chem. 1988, 36 (4), 752–753. (8) Todd, D. B.; Elgin, J. C. Phase equilibrium in systems with Ethylene above its critical Temperature Thermodynamics. AIChE J. 1955, 1, 20–7. (9) Wright, R. H. The Musk Odour. Perfum. Essent. Oil Rec. 1967, 58 (9), 648–650. 5726
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