J. of Supercritical Fluids 52 (2010) 56–61
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Extraction of sesame seed (Sesamun indicum L.) oil using compressed propane and supercritical carbon dioxide Marinês P. Corso a , Márcia R. Fagundes-Klen a , Edson A. Silva a , Lúcio Cardozo Filho b , Juciara N. Santos c , Lisiane S. Freitas c , Cláudio Dariva c,∗ a b c
Universidade Estadual do Oeste do Paraná, UNIOESTE, Rua da Faculdade, 645, 85903-000 Toledo, Paraná, Brazil Universidade Estadual de Maringá, UEM, Av. Colombo, 5790, Bloco D-90, 87020-900 Maringá, Paraná, Brazil Instituto de Tecnologia e Pesquisa, Universidade Tiradentes, PEP/UNIT, Av. Murilo Dantas, 300, 49032-490 Aracaju, Sergipe, Brazil
a r t i c l e
i n f o
Article history: Received 15 July 2009 Received in revised form 8 November 2009 Accepted 25 November 2009 Keywords: Carbon dioxide Mathematical modeling Oxidative stability Propane Sesame seed Supercritical fluid extraction
a b s t r a c t This work is aimed to investigate the extraction of sesame seed (Sesamun indicum L.) oil using supercritical carbon dioxide and compressed propane as solvents. The extractions were performed in a laboratory scale unit in a temperature and pressure range of 313–333 K and 19–25 MPa for carbon dioxide and 303–333 K and 8–12 MPa for propane extractions, respectively. A 22 factorial experimental design with three replicates of the central point was adopted to organize the data collection for both solvents. The results indicated that solvent and density were important variables for the CO2 extraction, while temperature is the most important variable for the extraction yield with propane. The extraction with propane was much faster than that with carbon dioxide due to the fact that propane is a better solvent for vegetable oils compared to carbon dioxide. On the other hand, characteristics of extracted oil, its oxidative stability determined by DSC and chemical profile of constituent fatty acids determined by gas chromatography, were similar to both solvents. The mathematical modeling of the extraction kinetics using a second order kinetic presented good results for the extraction with both solvents. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Among several distinct vegetables oils, the sesame oil (Sesamum indicum L.) is an important source of edible oil due to its high essential fatty acids (-3e6) sterols, tocopherols and tocotrienols concentration [1–5]. The industrialization of vegetable oils is a very important activity for food, cosmetic and pharmaceutical industries. In this context, adequate extraction oil process is desired considering environmental aspects and final product quality [6]. Many conventional processes for vegetable oil production involves mechanic milling followed by using liquid organic solvents in the extraction and solvent recuperation by distillation [7]. An alternative process to minimize the use of liquid organic solvents and facilitate the solvent recovery is the use of pressurized fluids. The extraction with pressurized fluids permits the efficient removal of triglycerides from vegetable oils, enables one to easy separation of solvent, oil and residue of the process, permitting to obtain products in the absence of solvent [6,8,9]. Despite the advantages of the extraction using pressurized fluids, this technique requires the understanding of the phase behavior between solvent and oil, and the knowledge of the extrac-
∗ Corresponding author. Tel.: +55 79 32182115; fax: +55 79 32182190. E-mail address:
[email protected] (C. Dariva). 0896-8446/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.supflu.2009.11.012
tion kinetic and a chemical composition of the products to avoid the use of severe conditions of temperature and pressure that result in high energetic and equipments costs [10]. Due to the physicochemical characteristics of the carbon dioxide, most papers involving supercritical fluid extraction of vegetable oils use carbon dioxide as solvent [11]. However, studies by Acosta et al. [12], Illés et al. [13], Hegel et al. [14], Hamdan et al. [15] and Freitas et al. [16], suggested that propane has the potential to be a highly effective solvent for vegetable oil extraction due to the high solubility of these compounds in propane. Some priori studies with sesame seeds can be found in the literature regarding the use of CO2 and ethanol as co-solvent in the extraction of the oil [4,17], the modeling and experimental measurement of phase equilibrium at high pressure associated with such a system [9,12,18], the development of an extraction process using gases [19], the evaluation of antioxidant activity of the resultant oil [4,5] and the characterization/identification of phytosterols present in the sesame oil extract [20]. However, there is a lack of information in the literature regarding a comparison between extraction using supercritical CO2 and compressed propane which focuses on the kinetic of extraction, and evaluation of data and modeling, chemical of constituent fatty acids, and evaluation of the oxidative stability of the extracted oil. Extraction yields and kinetics of the extraction are reported in this work. The characteristics of extracted oil are determinate by anal-
M.P. Corso et al. / J. of Supercritical Fluids 52 (2010) 56–61
ysis of FAMES and by the determination of its oxidative stability using DSC analysis. The protein content in the residue of all extractions was also measured. The extraction results are compared with the ones obtained for the exhaustive extraction with n-hexane. 2. Materials and methods 2.1. Sample preparation Sesame seeds (S. indicum L.) of the variety CNPA-G4 used in the experiments were kindly provided by Empresa Brasileira de Pesquisa Agropecuária - Embrapa (Bahia, Brazil). Initially, the seeds were dried in circulation air oven (Nova Ética, model 400/4ND, Brazil) at 308 K for 12 h, until achieve moisture content of 2.1%. The dried seeds were milled using a knives mill (Framo-Geratetechnik, model A 70, Germany) to produce particles of a mean diameter of 0.72 mm. 2.2. Determination of moisture content and diameter of particles
winitial − wdry wdry
2.5. Fatty acids analysis The quantitative analysis of fatty acids in sesame oil was performed in a gas chromatograph (VARIAN, model CP 3800), equipped with a split/splitless injector and FID detector, using a capillary column DB-5 (0.25 mm i.d. × 30 m, film thickness 0.25 m – J&W Scientific, USA). The initial temperature of the column was maintained at 443 K for 1 min, and then programmed to 483 K at a rate of 10 K/min and after to 503 K at 5 K/min, maintained at this final temperature for 5 min. Hydrogen (White Martins S.A., 99.999% of purity) was utilized as carrier gas, with a flow rate of 1.5 cm3 /min. The analysis was performed with detector and injector temperature of 503 K, and 1 L injection with split 1:10. In order to perform the analysis of total fatty acids content by gas chromatography, a derivatization of oil with methanol was conducted following a AOAC standard method 969.33 [24]. For the quantification of acids, authentic standards and methyl heptadecanoate ester as internal standard were used.
2.6. Analysis of the oil oxidative stability
Moisture content (H) of the sesame seeds samples was determined by the oven method [21]. The samples were weighed to the nearest 5 g in Petri dishes weighing and then were dried oven at 105 ◦ C for 24 h. After the sample was cooled in a desiccator over silica gel (0% RH) and reweighed. Moisture content was determined as: H = 100 ×
57
(1)
where winitial is mass initial and wdry is mass dry. The medium diameter of the particles was determined by electronic microscopy (model BX41 CoolSNAP-Procf, Olympus) connected with the software Image-Pro Plus. 2.3. Supercritical fluids extraction procedures The extraction experiments were conducted in a laboratory scale supercritical extraction unit, described in details by Souza et al. [22], using carbon dioxide (White Martins S.A., 99.5% of purity) and propane (linde gas, 99.5% of purity pure) as solvents. A factorial experimental design with two factors, two levels and a central point were employed to organize the experiments and data collection. Temperature and pressure were used as independent variables, while dependent variable was the extraction yield (mass of oil extracted/mass of dried seed). The CO2 extraction experiments were conducted in temperatures from 313 to 333 K, pressures from 19 to 25 MPa and constant flow rate of 3 cm3 /min. Propane extraction was performed in temperatures from 303 to 333 K, pressures from 8 to 12 MPa and constant flow rate of 0.8 cm3 /min. The mass flow rate of the solvent was determined based on the solvent density at the syringe pump that was maintained at 7 ◦ C through a recirculation water bath. For all solvents, extractions were conducted with approximately 17 g of dried and milled sesame seeds. 2.4. Classical extraction In order to determine the amount of oil in the sesame seeds, exhausting extractions were performed in a Soxhlet extractor (Nova Etica, Brazil). Approximately 12 g of sesame seeds, prepared as described in Section 2.1, were extracted in Soxhlet for 20 h according to the procedure described by Gómez et al. [23], at the boiling point of hexane.
Extracted oils (5.0 + 0.5 mg) at the limit conditions of temperature and pressure for propane and CO2 were used for the analysis. The oxidative stability of the sesame oil was determined according to Tan et al. [25]. Samples were inserted into platinum capsules, and differential scanning calorimetric (DSC) (NETZSCH, model STA 409 PG) conducted at four distinct temperatures (383, 393, 403 and 413 K) in contact with a flow of 50 cm3 /min of oxygen (White Martins S.A., 99.9% pure).
2.7. Determination of protein in the sesame seed The protein content of the sesame seed was determined according the procedure describe by Souza et al. [22]. The nitrogen total percentage of the sesame seed in each residue of extraction was analyzed by Kjeldahl method [19]. All analyses were performed in duplicate.
2.8. Kinetics of the sesame oil extraction To describe the kinetics of extraction, the phenomenological [26–30] or empiric [31,22] extraction models can be used. The kinetic curve of sesame oil extraction using supercritical CO2 and pressurized propane was modeled using an empirical second order kinetic model [22]. The mathematical model proposed considers the following hypotheses: (i) isothermal and isobaric process, (ii) the axial dispersion in the extractor is assumed negligible, (iii) at the beginning of the process the system is in equilibrium, i.e. the oil concentration in the fluid phase is equal to the equilibrium concentration, (iv) the oil was treated as pseudocomponent, and (v) the model is mono-dimensional and only the flow coordinate is considered. The mass balance equation for the oil in the fluid phase results in the following differential equation: ∂C ∂C ∂q +u =0 + bed ε ∂t ∂z ∂t
(2)
where C is the oil concentration in the solvent (kg/cm3 ), q is the oil concentration in the solid matrix (kg oil/kg solid), bed is the density in the bed (kg/cm3 ), u is the interstitial velocity (cm/min), t is the extraction time (min), ε is the bed porosity, and z is the coordinated in axial direction of the bed (cm). The second order extraction model represented by Eq. (3) assumes that the extraction rate is proportional to the product of the extraction driving force in
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fluid phase and the oil concentration in the solid matrix.
3. Results and discussion
∂q = −Kq(Ceq − C) ∂t
(3)
where K is kinetic constant (cm3 /kg min); Ceq is the equilibrium concentration of the oil in the solvent (kg oil/cm3 ). The initial and boundary conditions are expressed by Eqs. (3) and (4) respectively. C(0, z) = Ceq
C(t, 0) =
and
q(0, z) = q0
(4)
Ceq , t = 0 0, t>0
(5)
where q0 (kg oil extracted/kg inert solid) is the initial oil concentrate in the solid matrix after extractor pressurization stage. Eq. (5) represents the analytical solution of the model: C = Ceq
1−
0, 1 , (eA + e−B − 1)eB
t < tr (6)
t > tr
where tr = (L/u) is the residence time (min), L is the length (m) of column and u is the interstitial velocity (m/min), A = (z/u)ˇ , B = (−tu + z)ˇ/␣u, ˇ = KCeq ˛ and ˛ = bed q0 /εCeq . The mass of oil extracted as a function of time was calculated by the following equation:
te
moil =
Cout QF dt 0
=
Ceq QF t, Ceq QF ˛ Ceq tQF − ln(ezˇ/u + e(−(t v+z)ˇ)/˛u − 1), ˇ
t < tr t < tr
(7)
where QF is the volumetric fluxes of solvent and Cout is the concentration of the oil in the fluid phase at the extractor outlet. The constant K was determined minimizing the following objective function:
n exp
F=
(mMOD − mEXP ) oil oil
2
(8)
j
j
j=1
where mMOD is the calculated mass of the oil extracted; mEXP is the oil oil j
j
mass of oil experimentally obtained, and n exp is the number of experimental data in the kinetic curve.
3.1. Extraction yield Table 1 presents the experimental conditions for the extraction of sesame seed oil using carbon dioxide and propane as solvents. The extraction yield was calculated as the mass of the oil extracted by the mass of raw material fed into the extractor. The calculation of the extraction yield was performed at a fixed mass of pressurized solvents in order to permit a direct comparison among distinct experimental conditions: 450 g for the carbon dioxide extractions and 40 g in the cases of propane extractions. The total time of extraction was distinct depending on the experimental condition, attempting for an exhaustive extraction with the compressed solvents. The time of extraction of each experimental run was used for the calculation of the extraction percent in comparison with the extraction yield obtained by the extraction with n-hexane (Soxhlet extraction). The apparent solubility was calculated from the linear part of the extraction curve (extracted oil mass/mass of used solvent). The exhaustive extraction with n-hexane performed at the solvent boiling point during 20 h indicated an extraction yield of 52.6% in relation to the raw material fed into the reactor (standard deviation of 1.6% based on three replicates runs). The effect of density and temperature in the extraction with carbon dioxide as solvent indicated that both variables present positive effect on the extraction yield. The comparison of runs 1 and 2 at 313 K and runs 3 and 4 at 333 K suggests that the increase in density at fixed temperature promotes the enhancement in the extraction yield. The effect of temperature can be visualized by the comparison of runs 1 (313 K), 5 (323 K) and 4 (333 K) where the carbon dioxide density is approximately the same. It can be noted that the increase of temperature at constant density induces the increase in the extraction yield. These effects are in agreement with literature ones, as the solubility of vegetable oil in CO2 is favored by increment in the temperature and density [16,32]. For extraction using propane as compressed solvent, the effect of temperature is more pronounced that of pressure, as in the experimental conditions investigated propane is a compressed liquid and the changing in density is less pronounced with the variation of pressure. It can also be noted in Table 1 that the extractions with propane are much faster than those with carbon dioxide as solvent. This can also be evaluated by the apparent solubility as calculated in the last column of Table 1. This aspect is related to the fact that propane is a better solvent for triacylglycerols than carbon dioxide [16,15,33–35].
Table 1 Experimental conditions and extraction yield results for the sesame seed extraction CO2 , propane, and hexane as solvents. Run
Solvent
T (K)
P (MPa)
(kg/cm3 )
Extraction yielda (%)
Time of extraction (min)
Extraction percentb (%)
Apparent solubility (kg/kg)c
1 2 3 4 5d 6 7 8 9 10d 11
CO2 CO2 CO2 CO2 CO2 Propane Propane Propane Propane Propane Hexane
313 313 333 333 323 303 303 333 333 318 –
19 25 19 25 22 8 12 8 12 10 –
830 880 710 790 810 505 515 460 475 490 –
26.0 35.0 13.8 33.8 30.0 22.9 27.4 32.5 34.1 33.5 52.6
720 510 1380 570 690 70 65 50 55 40 1200
68.0 67.4 65.4 69.3 67.8 57.3 62.6 66.9 72.1 63.2 100.0
4.0 × 10−3 7.0 × 10−3 2.0 × 10-3 4.0 × 10−3 4.3 × 10−3 0.243 0.401 0.617 0.576 0.725 –
a 100 times the mass of oil extracted by the mass of raw material fed. The extraction yields for the CO2 runs were calculated using the mass of oil extracted corresponding to the time of 450 g of fed CO2 and for n-propane, the extraction yields were calculated using the mass of oil extracted corresponding to the time of 40 g of fed n-propane. b 100 times the mass of oil extracted at the ending of total extraction time by the mass of the oil extracted with hexane. c The apparent solubility was calculated from the linear part of the extraction curve (extracted oil mass/mass of used solvent). d Average value of three replicates runs.
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59
Table 2 Quantification of fatty acids in the sesame oil extracted with solvents (CO2 , propane and hexane). CO2
Fatty acidsa Lauric Myristic Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Araquidic Behenic a
Propane
Hexane
Run 1 (T = 313 K, P = 19 MPa)
Run 2 (T = 313 K, P = 25 MPa)
Run 3 (T = 333 K, P = 19 MPa)
Run 4 (T = 333 K, P = 25 MPa)
Run 5 (T = 323 K, P = 22 MPa)
Run 6 (T = 303 K, P = 8 MPa)
Run 7 (T = 303 K, P = 12 MPa)
Run 8 (T = 333 K, P = 8 MPa)
Run 9 (T = 333 K, P = 12 MPa)
Run 10 (T = 318 K, P = 10 MPa)
Run 11
0.0 0.0 10.5 0.1 5.2 37.1 46.2 0.3 0.5 0.1
0.0 0.2 10.4 0.3 5.0 36.1 46.9 0.5 0.5 0.1
0.0 0.1 11.0 0.3 4.9 36.1 46.8 0.4 0.4 0.0
0.1 0.1 10.3 0.3 5.0 36.2 47.1 0.4 0.6 0.1
0.0 0.0 10.5 0.2 5.3 37.0 45.9 0.3 0.6 0.1
0.0 0.0 10.3 0.2 5.2 37.5 45.8 0.3 0.6 0.1
0.0 0.0 10.4 0.3 5.2 36.8 46.3 0.4 0.5 0.1
0.0 0.0 10.3 0.5 5.3 36.7 46.2 0.3 0.5 0.1
0.0 0.1 10.3 0.1 5.2 37.8 45.7 0.3 0.3 0.2
0.0 0.1 10.1 0.2 5.3 37.5 46.0 0.3 0.4 0.0
0.0 0.0 10.3 0.2 5.2 36.4 46.8 0.4 0.6 0.1
Results in g/100 g of oil.
3.2. Composition of the sesame oil
3.3. Oxidative stability of sesame oil
Table 2 presents the quantification of fatty acids in the sesame oil extracted using supercritical carbon dioxide, pressurized propane, and hexane as analyzed by gas chromatography. The chemical profile of the fatty acids was similar to that obtained by Odabasi and Balaban [17]. An analysis of variance of the effects of temperature, pressure and solvent extractor indicated that there is no significant difference in the chemical distribution of fatty acid for the temperature and pressure range investigated in this work. Also, the extraction with carbon dioxide, propane and hexane produce sesame oil with similar fatty acid distribution considering a level of significance of 5% (p > 0.05) in the ANOVA test. Freitas et al. [16] working with the extraction of grape seed oil with carbon dioxide and propane also found that these solvents did not influence significantly the fatty acid distribution in the oil extracted.
The oxidative stability of a vegetable oil is dependent of the antioxidant amount of the raw material quality and of the conditions of processing and storage [36]. The sesame oil is considered an oil with high oxidative stability in function of the presence of natural antioxidant as tocopherols, sesamol and others lignans [37]. The analysis of the oxidative stability of vegetable oils by differential scanning calorimetry (DSC) as proposed by Tan et al. [25] was used to determinate the time of oxidative induction (t0 ) in samples of the oil extracted at the limit conditions of temperature and pressure for each solvent studied. Table 3 shows the oxidative induction time (t0 ), and logarithm equations relating isotherms with t0 obtained for temperatures of 383, 393, 403 and 413 K in the DSC analysis for the selected obtained for the extracted oil samples with the pressurized fluids and n-hexane as solvents.
Table 3 Sesame seed oil oxidative induction time obtained by DSC analysis of oils extracted with propane, CO2 and hexane as solvents. Process condition Solvent
CO2 CO2 Propane Propane Hexane
t0 (min) T (K)
P (MPa)
313 333 303 333 Boiling point
R2
Linear regression
T in DSC analysis (K)
25 19 8 12 0.1
383
393
403
413
417 393 360 405 295
215 199 191 – 104
96 107 100 96 62
66 52 62 62 34
T = 476.2 − 35.7 log10 T = 481.0 − 39.0 log10 T = 481.7 − 37.0 log10 T = 468.0 − 33.3 log10 T = 460.7 − 32.0 log10
t0 t0 t0 t0 t0
0.991 0.992 0.998 0.908 0.986
Table 4 Protein composition on the residue of extraction of sesame seed with compressed carbon dioxide, propane and hexane as solvent. Run
Solvent
T (K)
P (MPa)
Protein (%) ¯ ± a M
1 2 3 4 5 6 7 8 9 10 11 a b
CO2 CO2 CO2 CO2 CO2 Propane Propane Propane Propane Propane Hexane
313 313 333 333 323 303 303 333 333 318 Boiling point
19 25 19 25 22 8 12 8 12 10 0.1
¯ = average, = standard deviation. M Protein content in a free basis of oil. The total oil content was considered as the extraction yield obtained by Soxhlet.
32.7 32.5 31.8 33.2 32.5 29.4 31.2 32.6 34.0 31.1 43.3
± ± ± ± ± ± ± ± ± ± ±
Free oil basisb 0.2 0.1 0.2 0.4 0.6 0.5 0.2 0.3 0.1 0.2 0.6
48.1 48.2 48.6 47.9 48.0 51.3 49.8 48.7 47.1 49.2 43.3
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Table 5 Experimental conditions of the runs, initial concentration of oil in solid, concentration at equilibrium of oil in bulk and parameters fitted to the model. Solvent CO2 T (K) P (MPa) bed (kg/cm3 ) q0 (kg/kg) Ceq (kg/cm3 ) K (×106 cm3 /(kg min))
313 19 198 0.562 3 17.13
n-Propane 313 25 199 0.548 6 4.06
333 19 202 0.539 2 29.32
333 25 196 0.576 5 4.03
323 22 206 0.537 4 5.35
The results presented in Table 3 indicated the temperature and pressure did not present significant effect (p > 0.05) on the oxidative stability for the four oils extracted with compressed fluids. On the other hand, the oil extracted with n-hexane had lower oxidative stability, probably due to the higher temperature and time of extraction compared to the oils extracted with compressed solvents. Freitas et al. [16] compared the composition of free fatty acids in grape seed oil extracted with propane at 303 and 318 K. The authors found a smaller quantity of these chemical compounds at 303 K than at 318 K, suggesting that the hydrolysis of triacilglycerols in free fatty acids is related to the extraction temperature. In the work of Tan et al. [25], induction oxidative time for sesame oil was 542.7 min for DSC analysis at 383 K, 251.7 min at 393 K, 139.4 min at 403 K and 69.6 min at 413 K. The sesame oils used in this study was a commercial one where the addition of synthetic antioxidant in the vegetable oil could be responsible for the increment in t0 values for the sesame oil sample. The induction time and oxidation temperature showed linear behavior with regression coefficient (R2 ) more than 0.9, allowing prediction of the oxidative stability for the extracted oils when the temperature of exposure is a known variable. 3.4. Protein composition in sesame meal The protein composition in residue of the extraction of the sesame seed is presented in Table 4. The extraction with n-hexane showed a higher percent of protein in the residue of extraction than the others extraction with the compressed fluids. It is important to note that for this extraction almost the all lipid content was removed in the extraction process, unlike the samples extracted with compressed solvents and, in this sense, the protein percent is reduced is a function of the vegetable oil still present in the residue.
Fig. 1. Experimental and modeled kinetics curves for the extraction of sesame seed oil with carbon dioxide as solvent: (䊉) T = 313 K and P = 25 MPa, () T = 333 K and P = 25 MPa, (♦) T = 323 K and P = 22 MPa, () T = 313 K and P = 19 MPa, (+) T = 333 K and P = 19 MPa, (—) simulation-I, (· · ·) simulation-II.
303 8 218 0.303 126 0.660
303 12 204 0.255 227 0.257
333 8 198 0.211 299 0.256
333 12 189 0.352 401 0.167
318 10 207 0.198 357 0.306
Fig. 2. Experimental and modeled kinetic curves for the extraction of sesame seed oil with propane as solvent () 303 K and 8 MPa, (䊉) 303 K and 12 MPa, () 333 K and 8 MPa, (+) 333 K and 12 MPa, (⊗) 318 K and 10 MPa, (—) simulation-I, (· · ·) simulationII.
A protein calculation on a oil-free basis of oil indicated that in all extractions runs with the compressed solvents, that of the proteinaceous residue of the extractions is higher than that of the residue from hexane extraction. 3.5. Mathematic modeling of the extraction For the modeling of the extraction curves, the values of the kinetic constant, K, was calculated by the optimization of the Golden Section Search method [38] for the extraction with supercritical carbon dioxide, while for extractions with propane, the parameters K an Ceq were estimated using the Simplex method [39]. Table 5 shows the temperature (T), pressure (P), density parameters of the fluids (F ), bed density (bed ), initial mass of the inert solid (q0 ), equilibrium concentration of the oil in the fluid (Ceq ) and of the kinetic constant (K), utilized in the mathematical model. Average values for kinetic constants of the experiments using carbon dioxide as solvent was 11.98 and 0.33 m3 /(kg min) for extractions with propane. The kinetic curves were calculated using individual K values for each experiment (simulation-I) and using the average values (simulation-II). Fig. 1 presents the experimental and modeled kinetic curves for the extractions using carbon dioxide as solvent, whereas Fig. 2 presents the results for propane extractions. It should be noted that using the individual or average values of K for carbon dioxide result in a reliable modeling of the experimental data, while for propane the using of average K value produces large deviations of the model in comparison with experimental values. 4. Conclusions This work investigates the extraction of the sesame seeds using carbon dioxide and propane as compressed solvents. For carbon
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dioxide extractions, temperature and density presented positive effects on the extraction yield. The results showed that the compressed propane is a suitable solvent for the extraction of the sesame oil in function of smaller times and pressures employed compared to carbon dioxide extraction. For propane extractions the temperature presented a more pronounced effect than pressure due to the small variation of density with the pressure change in the experimental range investigated. The protein quantity in the residue of the extraction and chemical profile of the extracted oils were similar with carbon dioxide and propane as solvents. The similarity in chemical composition of the fatty acids in the extracted oils could be responsible for the comparable oxidative stability of the extracted oils. The second order kinetic model employed represented adequately the experimental extraction kinetic curves for both solvents. References [1] M. Namiki, The chemistry and physiological functions of sesame, Food Res. Intern. 11 (1995) 281–329. [2] Q. Hu, J. Xu, S. Chen, F. Yang, Antioxidant activity of extracts of black sesame seed (Sesamun indicum L.) by supercritical carbon dioxide extraction, J. Agric. Food Chem. 52 (2004) 943–947. [3] J. Xu, S. Chen, Q. Hu, Antioxidant activity of brown pigment and extracts from black sesame seed (Sesamum indicum L.), Food Chem. 91 (2005) 79–83. [4] T.Y. Tunde-Akintunde, B.O. Akintunde, Some physical properties of sesame seed, Biosyst. Eng. 88 (2004) 127–129. [5] K.P. Suja, John T. Abraham, Selvam N. Thamizh, A. Jayalekshmy, C. Arumughan, Antioxidant efficacy of sesame cake extract in vegetable oil protection, Food Chem. 84 (2004) 393–400. [6] F. Temelli, Perspectives on supercritical fluid processing of fats and oils, J. Supercrit. Fluids 47 (2009) 583–590. [7] H.J. Kim, S.B. Lee, K.A. Park, I.K. Hong, Characterization of extraction and separation of rice bran oil rich in EFA using SFE process, Sep. Purif. Technol. 15 (1999) 1–8. [8] G.M. Acosta, R.L. Smith, K. Arai, High-pressure PVT behavior of natural fats and oils, trilaurin, triolein, and n-tridecane from 303 K to 353 K from atmospheric pressure to 150 MPa, J. Chem. Eng. Data 41 (1996) 961–969. [9] I. Gracia, M.T. García, J.F. Rodríguez, M.P. Fernández, A. de Lucas, Modelling of the phase behaviour for vegetable oils at supercritical conditions, J. Supercrit. Fluids 48 (2009) 189–194. [10] M.S. Diaz, E.A. Brignole, Modeling and optimization of supercritical fluid processes, J. Supercrit. Fluids 47 (2009) 611–618. [11] G. Brunner, Gas extraction, in: An Introduction to Fundamentals of Supercritical Fluids and the Applications to Separation Processes, Springer, Berlin, 1994. [12] G.M. Acosta, R.L. Smith Jr., J.E. Walsh, K.A. Boni, Beef shank fat solubility in supercritical carbon dioxide–propane mixtures and in liquid propane, J. Food Sci. 60 (1995) 983–987. [13] V. Illés, H.G. Daood, S. Perneczki, L. Szokonya, M. Then, Extraction of coriander seed oil by CO2 and propane at super- and subcritical conditions, J. Supercrit. Fluids 17 (2000) 177–186. [14] P.E. Hegel, M.S. Zabaloy, G.D.B. Mabe, S. Pereda, E.A. Brignole, Phase equilibrium engineering of the extraction of oils from seeds using carbon dioxide + propane solvent mixtures, J. Supercrit. Fluids 42 (2007) 318–324. [15] S. Hamdan, H.G. Daood, M. Toth-Markus, V. Illés, Extraction of cardamom oil by supercritical carbon dioxide and sub-critical propane, J. Supercrit. Fluids 44 (2008) 25–30. [16] L.S. Freitas, J.V. Oliveira, C. Dariva, R.A. Jacques, E.B. Caramão, Extraction of grape
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