- Email: [email protected]
Supercritical CO2 fractionation of jasmine concrete
60
The Journal of Super-critical Fluids, 1995,8, 60-65
Supercritical CO2 Fractionation of Jasmine Concrete Ernest0
Reverchon*
and Giovanna
Della Porta
Dipartimento di lngegneria Chimica e Alimentare, Universitd di Salerno, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy Domenico
Gorgoglione
Essences srl, Via V. Veneto 8, 84019 S. Marzano sul Sarno (SA), Italy Received May 16, 1994; accepted in revised form October 5, 1994
Jasmine fragrance is usually produced by hexane extraction. The extraction product called a “concrete,” undergoes further processing to separatefragrance compounds from undesired coextractives such as paraffins and fatty acid methyl esters. This study reports supercritical CO2 fractionation of jasmine concrete to avoid thermal degradation of the product and to prevent pollution of the environment with organic solvents. Multistage supercritical extraction was performed by increasing CO;! density in three successive steps from 0.28 to 0.84 g cm-3, thus providing the selective extraction of the different compounds that constitute jasmine concrete. A multistage separation was also performed to complete the extract fractionation. In this final stage of the process, paraffins were separated from the fragrance-related compounds. The resultant products were paraffin-free and showed a lower fatty acid methyl ester content than the traditional products derived by hexane extraction. Furthermore, a higher yield was obtained relative to the traditional process. Keywords:
supercritical fluid, extraction, jasmine, concrete, fractionation, volatile oil, absolute
INTRODUCTION Scenting extracts obtained from flowers are widely used in the perfumery industry and have a very high commercial value. In several cases, raw cosmetic materials are treated at an early stage to avoid degradation of their fragrance. Conventional steam distillation technique is unsuitable to process such materials, since it induces thermal degradation of many compounds contained in the flowers. It is for this reason that solvent extraction is used. The subsequent solvent vaporization gives rise to a quasi-solid product called a “concrete,” which contains fragrance compounds such as hydrocarbon terpenes, oxygenated terpenes, sesquiterpenes, oxygenated sesquiterpenes, and other flavoring compounds. Moreover, concrete can contain fatty acids and their methyl esters, diterpenes, and other high molecular weight lipophilic compounds. High percentages of paraffins (from 50 to 70% by weight and more), belonging to the cuticular waxes covering the surface of flowers, are present too. Since many industrial applications require products containing only fragrance compounds, the concrete has to 0896-8446/95/0801-0060$7.50/O
be further processed. In the case of jasmine concrete, a typical treatment is solubilization in a large excess of ethyl alcohol. The solution is then cooled at -30 ‘C and filtered to eliminate the precipitated waxes. The solution is concentrated by vacuum distillation at 35 “C and 20 mm Hg.’ This product is called an “absolute.” Jasmine concrete yields from 20 to 40% by weight of an absolute that contains all the fragrance compounds (among them linalool, benzyl acetate, benzyl benzoate, phytol) and fatty acid methyl esters. The latter compounds do not contribute to the scent of jasmine flowers but represent about 30% by weight of the absolute,2 and the absolute also contains from 11 to 27% of paraffins.’ Furthermore, jasmine concrete can be treated with superheated steam to obtain the so-called “volatile oil.” The yield of this product is about 10% by weight and contains no paraffins except for small quantities of fatty acid methyl esters. In this fraction, fragrance compounds of higher molecular weight are not extracted. For example, the volatile oil fraction contains smaller quantities of ben-
0 1995 PRA Press
The Journal of Supercritical Fluids, Vol. 8, No. I, 1995 zyl benzoate compared to its concentration in the corresponding absolute Unfortunately, the above conventional techniques inevitably produce thermal degradation of the fragrance and contamination with organic solvents. Supercritical-fluid extraction (SFE) with CO2 of flower fragrances can give rise to some problems when applied on an industrial scale. The flowers have to be processed near the harvesting fields that, as a rule, are located, far from the industrial sites. Moreover, flower extraction gives very low yields, requiring very high volumes of extraction solvent (fluid) and very large SFE plants are required to obtain industrial scale production. The supercritical-fluid extraction of jasmine flowers on the laboratory scale has been performed by Ranguram Rao et a1.3 These authors used supercritical CO2 both with and without the addition of selected cosolvents at a pressure of 120 bar and a temperature of 40 ‘C. A singlestage separation apparatus was used in their study. Their experiments yielded jasmine fragrance of 0.40% by weight using pure supercritical CO2 and yields up to 0.68% when using 3.5 mol % acetone in supercritical CO2 as a cosolvent. Gopalakrishnan and Narayanan2 attempted to fractionate jasmine concrete by using liquid CO2 at a pressure of 100 bar and a temperature of 20 ‘C. Liquid CO2 produced the coextraction of high quantities of fatty acids methyl esters (from 13 to 20% of the liquid product). Single-stage separation was used resulting in the precipitation of paraffins along with the odoriferous compounds. These researchers noted that a viscous product was obtained with a high wax content, which increased with extraction time.2 This study is concerned with the development of a new jasmine concrete fractionation process in which selective extraction is obtained by adjusting the supercritical CO* solvent power (i.e., density). The extraction process was coupled to a fractional separation technique consisting of two separation stages in series.4-6 The separation conditions in each separator were chosen on the basis of the equilibrium solubilities of the compound families under precipitation conditions.5s7 EXPERIMENTAL APPARATUS AND PROCEDURES The SFE apparatus used in this work mainly consisted of an extractor with an internal volume of 200 cm3. It was charged with 20 g of jasmine concrete that was warmed to 45 “C, and then mixed with 2-mm diameter glass beads. The charge was mixed to obtain a thin layer of jasmine concrete that covered the glass beads. This procedure was used to maximize the contact surface between the solute and the supercritical solvent. The solution at the exit of the extractor went through two separators in series in order to fractionate the extract. A CO2 flow rate of 0.8 kg h-l was used during all
Fractionation of Jasmine Concrete
61
L 1
TOT
:
1. GC trace of the jasmine concrete. 1 = benzyl acetate; 2 = benzyl benzoate; 3 = phytol; 4 = heptacosane; 5 = FAME m.w. 410; 6 = nonacosane; 7 = hentriacontane. Figure
the tests. The other elements of the apparatus were described in detail elsewhere.5v6 Materials. Moroccan jasmine concrete (Jasminum grandiflorum L.) was supplied by Chauvet (Seillans, France). Carbon dioxide, 99.99% purity, was supplied by SON (SocietB Ossigeno Napoli, Italy). Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS apparatus was a Varian (San Fernando, CA) model 3400 gas chromatograph equipped with a fused-silica column DB-5, (J&W Scientific, Folsom, CA) 30 m x 0.25-mm i.d., film thickness 0.25 pm. The GC apparatus was interfaced with an ion-trap mass spectrometric detector (ITS 40, “Magnum,” Finnigan Mat, San Jose, CA). The GC conditions were: oven temperature of 50 “C for 5 min, then programmed at 50 to 250 “C at 2 ‘C min-I, and a fixed isothermal hold at 250 “C. The percentage composition of the identified compounds were computed from the GC peak area without any correction factor. The compounds were identified by comparing their retention times and mass spectra with those of pure reference compounds. Mass spectra were also compared with those in the NIST and WILEY5 mass spectra libraries. EXPERIMENTAL RESULTS AND DISCUSSION As expected, jasmine concrete was found to have a complex composition. Its GC trace is shown in Figure 1, with compound identifications reported in Table I. To fractionate this mixture it was necessary to optimize the solvent power and the selectivity of supercritical CO2. Of course, when the solvent power increases, selectivity decreases. In the case of supercritical fluid CO;?, solvent power increases with density and temperature. For jasmine concrete fractionation, only limited variation in the extraction temperature can be tolerated due to the possible thermal degradation of the products.
62 Reverchon et al.
The Journal of Supercritical Fluids, Vol. 8, No. 1, 1995
TABLE I Identification of the Compounds Contained in the Jasmine Concrete and in its Fractions Produced by Supercritical CO2 Extraction. Product A: Extraction Performed at 80 bar, 40 ‘C; Product B: Extraction Performed at 85 bar, 40 “C; Product C: Extraction Performed at 200 bar, 40 “C.
Compound Benzaldehyde Benzene methanol C,H,O (m.w. 108) Linalool Benzyl acetate Methyl salicylate Phenylethyl acetate Indole Eugenol cis-Jasmone Methyl caprate Tetradecane a-Farnesene Hexenyl benzoate Benzoic acid methylester Methyl jasmonate Benzyl benzoate Hexadecene Methyl myristate Methyl hexadecadienoate Methyl palmitoleate Methyl palmitate Phytol Methyl linolenate FAME (m.w. 290) Methyl linoleate Methyl oleate Methyl eicosenoate Eicosane Methyl arachidate Heneicosane Tricosane Methyl heneicosane Methyl erucate Cyclic compound (m.w. 386) Methyl behenate
Pentacosane Heptacosane Methyl pentacosane Octacosane Paraffin (m.w. 394) FAME (m.w. 410) FAME (m.w. 410) Methyl heptacosane
Nonacosane
Squalene Methyl octacosane Triacsntane Methyl nonacosane
Hentriacontane
Methyl triacontane Tritriacontane
Rt (min) 12.5 23.1 26.4 28.3 33.2 35.3 40.0 42.1 46.5 49.4 53.6 55.4 56.5 60.3 61.6 65.1 71.3 75.5 76.0 77.0 77.6 80.2 81.2 85.2 87.4 88.4 89.2 94.1 96.8 97.5 100.9 102.0 105.0 106.0 107.2 108.6 110.0 114.2 117.1 118.1 119.4 120.3 121.1 123.4 126.1 129.2 132.0 134.2 139.8 144.6 154.3 158.3
A% tr. 0.31 12.26 62.35 tr. tr. 0.40 0.59 2.00 tr. 1.62 0.64 tr 0.30 12.61 0.20 0.31 0.33 3.74 0.80 0.40 0.28 0.82 0.04 -
B%
C%
0.08 0.08 0.25 0.90 0.53 0.14 0.55 0.31 0.67 0.54 0.15 0.26 28.31 0.96 1.25 28.55 6.90 4.23 11.81 11.97 0.63 0.25 0.91 -
0.67 0.23 1.30 3.11 0.06 0.54 1.10 0.19 7.14 3.37 1.59 31.08 7.24 1.18 0.21 0.33 0.72 0.80 35.38 3.77 -
Waxes % Concrete % 0.03 0.05 0.27 0.11 0.11 8.76 0.08 1.61 0.08 59.70 1.37 1.58 0.20 23.70 2.31 0.06
tr. 0.09 0.77 2.20 13.02 tr. tr. 0.36 0.37 0.70 tr. 0.22 0.61 0.37 tr. 0.20 8.05 2.74 0.58 tr. 0.97 0.45 5.79 1‘90 0.25 1.26 3.74 2.82 tr. 0.93 tr, 0.31 tr. 2.13 0.53 0.19 1.00 7.48 tr. 0.75 1.75 tr. 2.24 0.20 21.88 tr. 1.60 1.31 tr. 9.27 0.74 0.24
Rt = retention time, min; % computed by peak area without any correction factor; FAME = fatty acid
methyl ester; m. w. = molecular weight; tr. = traces, (area < 0.05%); - = non detectable;
The Journal of Super-critical Fluids, Vol. 8, No. 1, 1995
Fractionation of Jasmine Concrete
3
4ees sI:BB
Figure 2. GC trace of the jasmine cuticular waxes obtained by supercritical CO, extraction and fractionation (see in the text). Extraction performed at 85 bar, 40 “C. 1 = heptacosane; 2 = nonacosane; 3 = hentriacontane. Maximum selectivity is required to perform fractionation of compound mixtures having similar structures. Therefore, a multistage extraction process was used consisting of successive extraction steps performed by increasing CO2 density. This technique can produce the selective extraction of different compound families, since it takes advantage of their different solubilities in the supercritical solvent. In addition to multistage extraction, a fractional separation technique was used to selectively precipitate the paraffins that were solubilized by supercritical CO2 under the extraction conditions.5*7 This step avoids contaminating the liquid extract collected in the second separator. Gopalakrishnan and Narayanan2 reported that benzyl acetate and benzyl benzoate are the major components of jasmine volatile oil and of jasmine absolute, respectively. This evidence was also confirmed by our data in Table I, columns A and B. For this reason, these compounds were assumed as reference compounds to monitor the jasmine concrete fractionation. The composition of extracts changes continuously during the extraction process since compounds that show higher CO2 solubilities are more readily extracted than those with lower solubilities (higher molecular weight compounds and/or more polar compounds). Therefore, the development of the extract composition during each extraction stage was monitored by GC-MS. After each hour of processing, the extracted compounds were identified and their relative percentages were calculated. To obtain the best jasmine concrete fractionation several tests were performed at various extraction pressures. Different sequences of CO2 density increase were also investigated. The optimum extraction performance was obtained by operating in three successive steps at a temperature of 40 “C and at pressures of 80, 85, and 200 bar, respectively. Separation stages were set at a pressure of 80 bar, a temperature of 0 “C in the first separator and a pressure of 25 bar, a temperature of -10 ‘C in the second one. These
63
2
:b
Figure 3. GC traces of the fractions obtained by supercritical CO, extraction and fractionation (see in the text). 3a product A, extraction at 80 bar, 40 T; 3b product B, extraction at 85 bar, 40 “C; 3c product C, extraction at 200 bar, 40 “C. 1 = benzyl acetate; 2 = benzyl benzoate; 3 = phytol; 4 = FAME m.w. 410. conditions were chosen on the basis of previously studied fractional separation processes.5*6*8 Figure 2 shows the GC trace of the solid product precipitated in the first separator during the jasmine concrete fractionation. Only high molecular weight compounds were detected. The identification of these compounds is reported in Table I (column waxes) and confirms the high selectivity of the fractionation process: only the paraffinic fraction was collected. The main compound collected was n.nonacosane at 59.7%. The overall composition of this fraction is not very different from that of cuticular waxes coextracted by supercritical CO2 from the leaves.5T6s*9 The first extraction step was performed at a pressure of 80 bar and a temperature of 40 “C (CO2 density = 0.28 g cme3). The GC trace of the whole oil fraction collected in the second separator after this extraction step is shown in Figure 3a. The comparison of this GC trace with
64 Reverchon et al. those shown in Figures 1 and 2 demonstrates that only the lower molecular weight compounds were extracted and that none of the paraffins and higher molecular weight compounds were detected in this fraction. The yield was 17.25% by weight of the concrete charged into the extractor. The identification of the compounds constituting this fraction and their area percentages were reported in Table I, product A. As expected, the main compounds were, benzyl acetate (62.35%), bcnzyl benzoate (12.6 1%), linalool (12.26%), and phytol (3.74%). Only small amounts of fatty acid methyl esters were detected (overall percentage 2.67%). Their percentage is very small if compared with the results obtained by the previously mentioned authors.*y3 This product can thus be classified as the volatile oil contained in the jasmine concrete. This step of the process was about 9 h long at the stated operating conditions. The first extraction step was stopped when the benzyl-acetate peak was almost completely absent in the GC trace of the sample collected during the last extraction hour. Other compounds belonging to the fragrance fraction of jasmine concrete (like benzyl benzoate) had not yet been exhausted at this point of the process. The second step was performed at a pressure of 85 bar and a temperature of 40 “C and lasted about 10 h (product B). Despite the small increase of the extraction pressure, the CO2 density, 0.35 g cm-3, was about 25% higher than in the previous step. The GC trace of the liquid product collected in the second separator during this stage of the process is shown in Figure 3b. The comparison with the GC trace in Figure 3a demonstrates that higher molecular weight compounds were extracted with respect to product A. In particular, high contents of benzyl benzoate (28.31%) and phytol (28.55%) were obtained. Large quantities of various fatty acid methyl esters were also extracted (37.95%) but only very small quantity of paraffins were detected in this fraction. The paraffins fraction was exclusively n.tetradecane (0.3 1%). The detailed identification of the compounds constituting this fraction is reported in Table I, product B. Product B was mixed with the one (product A) collected in the first step of the process obtaining a more complex product. The cumulative yield (A + B) was 30.3% by weight of the concrete charged in the extractor. The comparison of this mixed product with product A showed that the linalool and benzyl acetate content decreased to 6.76 and 39.92%, respectively; while the content of benzyl benzoate and phytol increased up to 19.60 and 11.45%, respectively. The content of fatty acid methyl esters increased from 2.67 to 15.02%. This product was compared to the jasmine absolute obtained by the authors using the procedure developed by Anac’ and described in the introduction. This “conventional” absolute contained 34.32% of fatty acid methyl esters and 5.11% of paraffins from C2s to C2s. Benzyl acetate, benzyl benzoate, and phytol percentages in this product were 17.56,
The Journal of Supercritical Fluids, Vol. 8, No. I, 1995
15.97, and 10.61%, respectively. Therefore, the mixture of products A and B showed some similarities with the conventional absolute but also some remarkable differences; that is, supercritical CO2 extract was wax free, had a lower fatty acid methyl ester content, and had more than double the percentage of benzyl acetate than in the traditional product. Of course, if one is interested in obtaining the absolute-like fraction, it is possible to perform the whole extraction process at 40 “C, 85 bar, thus simultaneously extracting fractions A and B. The last extraction step started when the GC analysis of the extracts showed that the benzyl benzoate content in the extract was approximately 1%. It was performed at a pressure of 200 bar and a temperature of 40 “C (CO2 density = 0.84 g cme3) for about 3 h (product C, Figure 3~). The object of this stage of the process was to use high density CO:! to extract all the lipophilic compounds remaining in the concrete. In this manner, we could ascertain if all the compounds of interest had been completely extracted during the previous process steps. The identification of the compounds contained in this fraction is showed in Table I (column C). Benzyl acetate was not detected and benzyl benzoate was at 1.30%. The percentage of phytol was 7.14%. All the other extracted compounds were fatty acid methyl esters (83.07%) or paraffins (0.95%) Product C was a liquid and represented a yield of 18% by weight of the charge. During this stage of the process high yield of waxes was obtained in the first separator; 12% by weight of the concrete compared to 2% by weight obtained during the two previous steps of the process. Panel testinglo was performed to evaluate the sensory characteristics of the extracts. The odor of product A was judged as a light jasmine fragrance, rich in top notes. Product B had a strong jasmine fragrance, with more bottom notes than in product A. Product C, did not have the characteristic perfume shown by the previously extracted materials: it was almost devoid of odor. Therefore, it did not significantly contribute to the fragrance extracted and can be excluded from the perfume formulation. The jasmine concrete had a deep orange color while fractions A and B were light yellow. Fraction C was colorless. The process of concrete fractionation by supercritical CO2 could also be used to produce different fragrance fractions from those obtainable by the conventional techniques. For example, it is possible to perform the process in a different number of steps or to mix the various extracts obtained in a different manner. These procedures will allow the production of fragrances tailored to specific industrial requirements. Some concrete fractionation tests were performed on a supercritical-fluid pilot scale apparatus located at Essences (Salerno, Italy). This apparatus was equipped with a 20-dm3 extraction vessel and was described in detail in a previous work.” It was operated at the same conditions as the laboratory unit except for conditions in the
The Journal
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Super-critical Fluids, Vol. 8, No. 1, 1995
Fractionation of Jasmine Concrete
last separation stage that were chosen to allow CO;? recompression. These tests confirmed the results obtained on the laboratory apparatus. In each fractionation test, 2 kg of jasmine concrete were charged in the extractor and the process yielded a quantity of absolute that was 30% by weight of the charge; that is, more than 600 g of jasmine absolute (product A + B).
(3)
ACKNOWLEDGMENT The work was partly performed in the framework of Progetto Strategic0 “Tecnologie Chimiche Innovative,” C. N. R., Rome, Italy.
(8)
REFERENCES
(1) (2)
Anac, 0. Fluv. Frugr. J. 1986, I, 115. Gopalakrishnan, N.; Narayanan, C. S. Flav. Fragr. J. 1991,
6,
135.
(5) (6)
Ranguram Rao, G. V.; Srinivas, P.; Sastry, S. V. G. K.; Murhopadhyay, M. J. Supercrit. Fluids 1992,5, 19. Stahl, E.; Quirin, K. W.; Gerard, D. Verdichtete Case zur Extraktion und Raffination; Springer Verlag: Berlin, 1986. Reverchon, E. J. Supercrit. Fluids 1992,5, 256. Reverchon, E.; Senatore, F. J. Agric. Food Chem. 1994,42,
(7)
(9)
65
I,
154.
Reverchon, E.; Russo, P.; Stassi, A. J. Chem. Eng. Data 1993.38, 458. Reverchon, E.; Senatore, F. Flav. Fragr. J. 1992, 7, 227. Reverchon, E.; Ambruosi, A.; Senatore, F. Flav. Fragr. J. 1994,
9, 19.
(10) IFT, Sensory evaluation guide for testing food and beverage products, Food. Technol., 35, 50, 1981. (11) Reverchon, E.; Donsi, G.; Sesti OS&O, L. Ind. Eng. Chem. Res. 1993,32, 2721.
The Journal of Super-critical Fluids, 1995,8, 60-65
Supercritical CO2 Fractionation of Jasmine Concrete Ernest0
Reverchon*
and Giovanna
Della Porta
Dipartimento di lngegneria Chimica e Alimentare, Universitd di Salerno, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy Domenico
Gorgoglione
Essences srl, Via V. Veneto 8, 84019 S. Marzano sul Sarno (SA), Italy Received May 16, 1994; accepted in revised form October 5, 1994
Jasmine fragrance is usually produced by hexane extraction. The extraction product called a “concrete,” undergoes further processing to separatefragrance compounds from undesired coextractives such as paraffins and fatty acid methyl esters. This study reports supercritical CO2 fractionation of jasmine concrete to avoid thermal degradation of the product and to prevent pollution of the environment with organic solvents. Multistage supercritical extraction was performed by increasing CO;! density in three successive steps from 0.28 to 0.84 g cm-3, thus providing the selective extraction of the different compounds that constitute jasmine concrete. A multistage separation was also performed to complete the extract fractionation. In this final stage of the process, paraffins were separated from the fragrance-related compounds. The resultant products were paraffin-free and showed a lower fatty acid methyl ester content than the traditional products derived by hexane extraction. Furthermore, a higher yield was obtained relative to the traditional process. Keywords:
supercritical fluid, extraction, jasmine, concrete, fractionation, volatile oil, absolute
INTRODUCTION Scenting extracts obtained from flowers are widely used in the perfumery industry and have a very high commercial value. In several cases, raw cosmetic materials are treated at an early stage to avoid degradation of their fragrance. Conventional steam distillation technique is unsuitable to process such materials, since it induces thermal degradation of many compounds contained in the flowers. It is for this reason that solvent extraction is used. The subsequent solvent vaporization gives rise to a quasi-solid product called a “concrete,” which contains fragrance compounds such as hydrocarbon terpenes, oxygenated terpenes, sesquiterpenes, oxygenated sesquiterpenes, and other flavoring compounds. Moreover, concrete can contain fatty acids and their methyl esters, diterpenes, and other high molecular weight lipophilic compounds. High percentages of paraffins (from 50 to 70% by weight and more), belonging to the cuticular waxes covering the surface of flowers, are present too. Since many industrial applications require products containing only fragrance compounds, the concrete has to 0896-8446/95/0801-0060$7.50/O
be further processed. In the case of jasmine concrete, a typical treatment is solubilization in a large excess of ethyl alcohol. The solution is then cooled at -30 ‘C and filtered to eliminate the precipitated waxes. The solution is concentrated by vacuum distillation at 35 “C and 20 mm Hg.’ This product is called an “absolute.” Jasmine concrete yields from 20 to 40% by weight of an absolute that contains all the fragrance compounds (among them linalool, benzyl acetate, benzyl benzoate, phytol) and fatty acid methyl esters. The latter compounds do not contribute to the scent of jasmine flowers but represent about 30% by weight of the absolute,2 and the absolute also contains from 11 to 27% of paraffins.’ Furthermore, jasmine concrete can be treated with superheated steam to obtain the so-called “volatile oil.” The yield of this product is about 10% by weight and contains no paraffins except for small quantities of fatty acid methyl esters. In this fraction, fragrance compounds of higher molecular weight are not extracted. For example, the volatile oil fraction contains smaller quantities of ben-
0 1995 PRA Press
The Journal of Supercritical Fluids, Vol. 8, No. I, 1995 zyl benzoate compared to its concentration in the corresponding absolute Unfortunately, the above conventional techniques inevitably produce thermal degradation of the fragrance and contamination with organic solvents. Supercritical-fluid extraction (SFE) with CO2 of flower fragrances can give rise to some problems when applied on an industrial scale. The flowers have to be processed near the harvesting fields that, as a rule, are located, far from the industrial sites. Moreover, flower extraction gives very low yields, requiring very high volumes of extraction solvent (fluid) and very large SFE plants are required to obtain industrial scale production. The supercritical-fluid extraction of jasmine flowers on the laboratory scale has been performed by Ranguram Rao et a1.3 These authors used supercritical CO2 both with and without the addition of selected cosolvents at a pressure of 120 bar and a temperature of 40 ‘C. A singlestage separation apparatus was used in their study. Their experiments yielded jasmine fragrance of 0.40% by weight using pure supercritical CO2 and yields up to 0.68% when using 3.5 mol % acetone in supercritical CO2 as a cosolvent. Gopalakrishnan and Narayanan2 attempted to fractionate jasmine concrete by using liquid CO2 at a pressure of 100 bar and a temperature of 20 ‘C. Liquid CO2 produced the coextraction of high quantities of fatty acids methyl esters (from 13 to 20% of the liquid product). Single-stage separation was used resulting in the precipitation of paraffins along with the odoriferous compounds. These researchers noted that a viscous product was obtained with a high wax content, which increased with extraction time.2 This study is concerned with the development of a new jasmine concrete fractionation process in which selective extraction is obtained by adjusting the supercritical CO* solvent power (i.e., density). The extraction process was coupled to a fractional separation technique consisting of two separation stages in series.4-6 The separation conditions in each separator were chosen on the basis of the equilibrium solubilities of the compound families under precipitation conditions.5s7 EXPERIMENTAL APPARATUS AND PROCEDURES The SFE apparatus used in this work mainly consisted of an extractor with an internal volume of 200 cm3. It was charged with 20 g of jasmine concrete that was warmed to 45 “C, and then mixed with 2-mm diameter glass beads. The charge was mixed to obtain a thin layer of jasmine concrete that covered the glass beads. This procedure was used to maximize the contact surface between the solute and the supercritical solvent. The solution at the exit of the extractor went through two separators in series in order to fractionate the extract. A CO2 flow rate of 0.8 kg h-l was used during all
Fractionation of Jasmine Concrete
61
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1. GC trace of the jasmine concrete. 1 = benzyl acetate; 2 = benzyl benzoate; 3 = phytol; 4 = heptacosane; 5 = FAME m.w. 410; 6 = nonacosane; 7 = hentriacontane. Figure
the tests. The other elements of the apparatus were described in detail elsewhere.5v6 Materials. Moroccan jasmine concrete (Jasminum grandiflorum L.) was supplied by Chauvet (Seillans, France). Carbon dioxide, 99.99% purity, was supplied by SON (SocietB Ossigeno Napoli, Italy). Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS apparatus was a Varian (San Fernando, CA) model 3400 gas chromatograph equipped with a fused-silica column DB-5, (J&W Scientific, Folsom, CA) 30 m x 0.25-mm i.d., film thickness 0.25 pm. The GC apparatus was interfaced with an ion-trap mass spectrometric detector (ITS 40, “Magnum,” Finnigan Mat, San Jose, CA). The GC conditions were: oven temperature of 50 “C for 5 min, then programmed at 50 to 250 “C at 2 ‘C min-I, and a fixed isothermal hold at 250 “C. The percentage composition of the identified compounds were computed from the GC peak area without any correction factor. The compounds were identified by comparing their retention times and mass spectra with those of pure reference compounds. Mass spectra were also compared with those in the NIST and WILEY5 mass spectra libraries. EXPERIMENTAL RESULTS AND DISCUSSION As expected, jasmine concrete was found to have a complex composition. Its GC trace is shown in Figure 1, with compound identifications reported in Table I. To fractionate this mixture it was necessary to optimize the solvent power and the selectivity of supercritical CO2. Of course, when the solvent power increases, selectivity decreases. In the case of supercritical fluid CO;?, solvent power increases with density and temperature. For jasmine concrete fractionation, only limited variation in the extraction temperature can be tolerated due to the possible thermal degradation of the products.
62 Reverchon et al.
The Journal of Supercritical Fluids, Vol. 8, No. 1, 1995
TABLE I Identification of the Compounds Contained in the Jasmine Concrete and in its Fractions Produced by Supercritical CO2 Extraction. Product A: Extraction Performed at 80 bar, 40 ‘C; Product B: Extraction Performed at 85 bar, 40 “C; Product C: Extraction Performed at 200 bar, 40 “C.
Compound Benzaldehyde Benzene methanol C,H,O (m.w. 108) Linalool Benzyl acetate Methyl salicylate Phenylethyl acetate Indole Eugenol cis-Jasmone Methyl caprate Tetradecane a-Farnesene Hexenyl benzoate Benzoic acid methylester Methyl jasmonate Benzyl benzoate Hexadecene Methyl myristate Methyl hexadecadienoate Methyl palmitoleate Methyl palmitate Phytol Methyl linolenate FAME (m.w. 290) Methyl linoleate Methyl oleate Methyl eicosenoate Eicosane Methyl arachidate Heneicosane Tricosane Methyl heneicosane Methyl erucate Cyclic compound (m.w. 386) Methyl behenate
Pentacosane Heptacosane Methyl pentacosane Octacosane Paraffin (m.w. 394) FAME (m.w. 410) FAME (m.w. 410) Methyl heptacosane
Nonacosane
Squalene Methyl octacosane Triacsntane Methyl nonacosane
Hentriacontane
Methyl triacontane Tritriacontane
Rt (min) 12.5 23.1 26.4 28.3 33.2 35.3 40.0 42.1 46.5 49.4 53.6 55.4 56.5 60.3 61.6 65.1 71.3 75.5 76.0 77.0 77.6 80.2 81.2 85.2 87.4 88.4 89.2 94.1 96.8 97.5 100.9 102.0 105.0 106.0 107.2 108.6 110.0 114.2 117.1 118.1 119.4 120.3 121.1 123.4 126.1 129.2 132.0 134.2 139.8 144.6 154.3 158.3
A% tr. 0.31 12.26 62.35 tr. tr. 0.40 0.59 2.00 tr. 1.62 0.64 tr 0.30 12.61 0.20 0.31 0.33 3.74 0.80 0.40 0.28 0.82 0.04 -
B%
C%
0.08 0.08 0.25 0.90 0.53 0.14 0.55 0.31 0.67 0.54 0.15 0.26 28.31 0.96 1.25 28.55 6.90 4.23 11.81 11.97 0.63 0.25 0.91 -
0.67 0.23 1.30 3.11 0.06 0.54 1.10 0.19 7.14 3.37 1.59 31.08 7.24 1.18 0.21 0.33 0.72 0.80 35.38 3.77 -
Waxes % Concrete % 0.03 0.05 0.27 0.11 0.11 8.76 0.08 1.61 0.08 59.70 1.37 1.58 0.20 23.70 2.31 0.06
tr. 0.09 0.77 2.20 13.02 tr. tr. 0.36 0.37 0.70 tr. 0.22 0.61 0.37 tr. 0.20 8.05 2.74 0.58 tr. 0.97 0.45 5.79 1‘90 0.25 1.26 3.74 2.82 tr. 0.93 tr, 0.31 tr. 2.13 0.53 0.19 1.00 7.48 tr. 0.75 1.75 tr. 2.24 0.20 21.88 tr. 1.60 1.31 tr. 9.27 0.74 0.24
Rt = retention time, min; % computed by peak area without any correction factor; FAME = fatty acid
methyl ester; m. w. = molecular weight; tr. = traces, (area < 0.05%); - = non detectable;
The Journal of Super-critical Fluids, Vol. 8, No. 1, 1995
Fractionation of Jasmine Concrete
3
4ees sI:BB
Figure 2. GC trace of the jasmine cuticular waxes obtained by supercritical CO, extraction and fractionation (see in the text). Extraction performed at 85 bar, 40 “C. 1 = heptacosane; 2 = nonacosane; 3 = hentriacontane. Maximum selectivity is required to perform fractionation of compound mixtures having similar structures. Therefore, a multistage extraction process was used consisting of successive extraction steps performed by increasing CO2 density. This technique can produce the selective extraction of different compound families, since it takes advantage of their different solubilities in the supercritical solvent. In addition to multistage extraction, a fractional separation technique was used to selectively precipitate the paraffins that were solubilized by supercritical CO2 under the extraction conditions.5*7 This step avoids contaminating the liquid extract collected in the second separator. Gopalakrishnan and Narayanan2 reported that benzyl acetate and benzyl benzoate are the major components of jasmine volatile oil and of jasmine absolute, respectively. This evidence was also confirmed by our data in Table I, columns A and B. For this reason, these compounds were assumed as reference compounds to monitor the jasmine concrete fractionation. The composition of extracts changes continuously during the extraction process since compounds that show higher CO2 solubilities are more readily extracted than those with lower solubilities (higher molecular weight compounds and/or more polar compounds). Therefore, the development of the extract composition during each extraction stage was monitored by GC-MS. After each hour of processing, the extracted compounds were identified and their relative percentages were calculated. To obtain the best jasmine concrete fractionation several tests were performed at various extraction pressures. Different sequences of CO2 density increase were also investigated. The optimum extraction performance was obtained by operating in three successive steps at a temperature of 40 “C and at pressures of 80, 85, and 200 bar, respectively. Separation stages were set at a pressure of 80 bar, a temperature of 0 “C in the first separator and a pressure of 25 bar, a temperature of -10 ‘C in the second one. These
63
2
:b
Figure 3. GC traces of the fractions obtained by supercritical CO, extraction and fractionation (see in the text). 3a product A, extraction at 80 bar, 40 T; 3b product B, extraction at 85 bar, 40 “C; 3c product C, extraction at 200 bar, 40 “C. 1 = benzyl acetate; 2 = benzyl benzoate; 3 = phytol; 4 = FAME m.w. 410. conditions were chosen on the basis of previously studied fractional separation processes.5*6*8 Figure 2 shows the GC trace of the solid product precipitated in the first separator during the jasmine concrete fractionation. Only high molecular weight compounds were detected. The identification of these compounds is reported in Table I (column waxes) and confirms the high selectivity of the fractionation process: only the paraffinic fraction was collected. The main compound collected was n.nonacosane at 59.7%. The overall composition of this fraction is not very different from that of cuticular waxes coextracted by supercritical CO2 from the leaves.5T6s*9 The first extraction step was performed at a pressure of 80 bar and a temperature of 40 “C (CO2 density = 0.28 g cme3). The GC trace of the whole oil fraction collected in the second separator after this extraction step is shown in Figure 3a. The comparison of this GC trace with
64 Reverchon et al. those shown in Figures 1 and 2 demonstrates that only the lower molecular weight compounds were extracted and that none of the paraffins and higher molecular weight compounds were detected in this fraction. The yield was 17.25% by weight of the concrete charged into the extractor. The identification of the compounds constituting this fraction and their area percentages were reported in Table I, product A. As expected, the main compounds were, benzyl acetate (62.35%), bcnzyl benzoate (12.6 1%), linalool (12.26%), and phytol (3.74%). Only small amounts of fatty acid methyl esters were detected (overall percentage 2.67%). Their percentage is very small if compared with the results obtained by the previously mentioned authors.*y3 This product can thus be classified as the volatile oil contained in the jasmine concrete. This step of the process was about 9 h long at the stated operating conditions. The first extraction step was stopped when the benzyl-acetate peak was almost completely absent in the GC trace of the sample collected during the last extraction hour. Other compounds belonging to the fragrance fraction of jasmine concrete (like benzyl benzoate) had not yet been exhausted at this point of the process. The second step was performed at a pressure of 85 bar and a temperature of 40 “C and lasted about 10 h (product B). Despite the small increase of the extraction pressure, the CO2 density, 0.35 g cm-3, was about 25% higher than in the previous step. The GC trace of the liquid product collected in the second separator during this stage of the process is shown in Figure 3b. The comparison with the GC trace in Figure 3a demonstrates that higher molecular weight compounds were extracted with respect to product A. In particular, high contents of benzyl benzoate (28.31%) and phytol (28.55%) were obtained. Large quantities of various fatty acid methyl esters were also extracted (37.95%) but only very small quantity of paraffins were detected in this fraction. The paraffins fraction was exclusively n.tetradecane (0.3 1%). The detailed identification of the compounds constituting this fraction is reported in Table I, product B. Product B was mixed with the one (product A) collected in the first step of the process obtaining a more complex product. The cumulative yield (A + B) was 30.3% by weight of the concrete charged in the extractor. The comparison of this mixed product with product A showed that the linalool and benzyl acetate content decreased to 6.76 and 39.92%, respectively; while the content of benzyl benzoate and phytol increased up to 19.60 and 11.45%, respectively. The content of fatty acid methyl esters increased from 2.67 to 15.02%. This product was compared to the jasmine absolute obtained by the authors using the procedure developed by Anac’ and described in the introduction. This “conventional” absolute contained 34.32% of fatty acid methyl esters and 5.11% of paraffins from C2s to C2s. Benzyl acetate, benzyl benzoate, and phytol percentages in this product were 17.56,
The Journal of Supercritical Fluids, Vol. 8, No. I, 1995
15.97, and 10.61%, respectively. Therefore, the mixture of products A and B showed some similarities with the conventional absolute but also some remarkable differences; that is, supercritical CO2 extract was wax free, had a lower fatty acid methyl ester content, and had more than double the percentage of benzyl acetate than in the traditional product. Of course, if one is interested in obtaining the absolute-like fraction, it is possible to perform the whole extraction process at 40 “C, 85 bar, thus simultaneously extracting fractions A and B. The last extraction step started when the GC analysis of the extracts showed that the benzyl benzoate content in the extract was approximately 1%. It was performed at a pressure of 200 bar and a temperature of 40 “C (CO2 density = 0.84 g cme3) for about 3 h (product C, Figure 3~). The object of this stage of the process was to use high density CO:! to extract all the lipophilic compounds remaining in the concrete. In this manner, we could ascertain if all the compounds of interest had been completely extracted during the previous process steps. The identification of the compounds contained in this fraction is showed in Table I (column C). Benzyl acetate was not detected and benzyl benzoate was at 1.30%. The percentage of phytol was 7.14%. All the other extracted compounds were fatty acid methyl esters (83.07%) or paraffins (0.95%) Product C was a liquid and represented a yield of 18% by weight of the charge. During this stage of the process high yield of waxes was obtained in the first separator; 12% by weight of the concrete compared to 2% by weight obtained during the two previous steps of the process. Panel testinglo was performed to evaluate the sensory characteristics of the extracts. The odor of product A was judged as a light jasmine fragrance, rich in top notes. Product B had a strong jasmine fragrance, with more bottom notes than in product A. Product C, did not have the characteristic perfume shown by the previously extracted materials: it was almost devoid of odor. Therefore, it did not significantly contribute to the fragrance extracted and can be excluded from the perfume formulation. The jasmine concrete had a deep orange color while fractions A and B were light yellow. Fraction C was colorless. The process of concrete fractionation by supercritical CO2 could also be used to produce different fragrance fractions from those obtainable by the conventional techniques. For example, it is possible to perform the process in a different number of steps or to mix the various extracts obtained in a different manner. These procedures will allow the production of fragrances tailored to specific industrial requirements. Some concrete fractionation tests were performed on a supercritical-fluid pilot scale apparatus located at Essences (Salerno, Italy). This apparatus was equipped with a 20-dm3 extraction vessel and was described in detail in a previous work.” It was operated at the same conditions as the laboratory unit except for conditions in the
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of
Super-critical Fluids, Vol. 8, No. 1, 1995
Fractionation of Jasmine Concrete
last separation stage that were chosen to allow CO;? recompression. These tests confirmed the results obtained on the laboratory apparatus. In each fractionation test, 2 kg of jasmine concrete were charged in the extractor and the process yielded a quantity of absolute that was 30% by weight of the charge; that is, more than 600 g of jasmine absolute (product A + B).
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ACKNOWLEDGMENT The work was partly performed in the framework of Progetto Strategic0 “Tecnologie Chimiche Innovative,” C. N. R., Rome, Italy.
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Anac, 0. Fluv. Frugr. J. 1986, I, 115. Gopalakrishnan, N.; Narayanan, C. S. Flav. Fragr. J. 1991,
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Ranguram Rao, G. V.; Srinivas, P.; Sastry, S. V. G. K.; Murhopadhyay, M. J. Supercrit. Fluids 1992,5, 19. Stahl, E.; Quirin, K. W.; Gerard, D. Verdichtete Case zur Extraktion und Raffination; Springer Verlag: Berlin, 1986. Reverchon, E. J. Supercrit. Fluids 1992,5, 256. Reverchon, E.; Senatore, F. J. Agric. Food Chem. 1994,42,
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Reverchon, E.; Russo, P.; Stassi, A. J. Chem. Eng. Data 1993.38, 458. Reverchon, E.; Senatore, F. Flav. Fragr. J. 1992, 7, 227. Reverchon, E.; Ambruosi, A.; Senatore, F. Flav. Fragr. J. 1994,
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(10) IFT, Sensory evaluation guide for testing food and beverage products, Food. Technol., 35, 50, 1981. (11) Reverchon, E.; Donsi, G.; Sesti OS&O, L. Ind. Eng. Chem. Res. 1993,32, 2721.