- Email: [email protected]
Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation
Journal of Food Engineering xxx (2016) 1e5
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation W.P. Silvestre a, c, *, F. Agostini b, L.A.R. Muniz a, G.F. Pauletti c a
Course of Chemical Engineering, Center of Exact Sciences and Technology, University of Caxias do Sul (UCS), Brazil Institute of Biotechnology, University of Caxias do Sul, Brazil c Course of Agronomy, Center of Biological and Health Sciences, University of Caxias do Sul, Brazil b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 August 2015 Received in revised form 29 December 2015 Accepted 14 January 2016 Available online xxx
This work aims to evaluate the technical viability of vacuum fractional distillation to separate the components of green mandarin (Citrus deliciosa Tenore) essential oil. Thermal degradation was also analyzed. The obtained results demonstrate that vacuum fractional distillation is capable to separate the hydrocarbon terpenes, which were removed from the top/stages of the column, from the terpenes with other chemical functions, which remained in the bottom. Some trace compounds, such as methyl-Nmethyl anthranilate (mass fraction of 0,006 in the raw oil) and alpha sinensal (mass fraction of 0,004 in the raw oil), had their concentrations increased more than ten times after the separation, to mass fraction of 0,153 and 0,109, respectively. The mass fraction of the major compound of the essential oil, Dlimonene, was reduced from 0,707 in the raw oil, to 0,218 in the bottom. There was no evidence of thermal degradation in the products of the separation. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Fractioning column Green mandarin essential oil Terpenes Vacuum distillation GC/MS
1. Introduction The harvest of citrus fruits presents great importance worldwide, as its production, in 2013, was approximately 111,5 millions of tons. The main citrus fruits are orange, lemon, mandarin and lime, which have a high commercial value as sell ‘in nature’ or as a raw material for food industry (Castro and Escobar, 2014). The peel and the bagasse of citrus represent 40e50% of total weight of the fruit and in general are waste of the processing of this raw material, being both used as biomass. The bagasse is also used as component in animal feeding. The peel has many bioactive components, as ascorbic acid, terpenes and flavonoids, which can be extracted and after purified for various applications (Castro and Escobar, 2014; Lohbauer, 2014). The citrus essential oil is a mixture of terpenes, many of them with important industrial applications, in medicine, pharmacology, cosmetics and food industry (Bonaccorsi et al., 2009). Tough, to have a practical application for the minority compounds (which, in general, have more value), it is necessary to properly separate the
* Corresponding author. Laboratory of Chemistry and Soil Fertility, University of polis, 95074-270, Caxias do Caxias do Sul, Road Francisco Getúlio Vargas, 1135, Petro Sul, RS, Brazil. E-mail address: [email protected] (W.P. Silvestre).
mixture of substances in the raw oil (Castro and Escobar, 2014; ~es et al., 2004). Embrapa, 2004; Simo The genetics of the plant determines its chemotype. However, the environmental conditions (climate, soil type, presence of nutrients) are capable of provoke considerable variations in the oil and in the very chemotype, featuring an ‘ecotype’ (Dellacassa, 2010). Is also important highlight that the composition of the essential oil obtained varies considerably between the parts of the plant, as well by the extractive process (Gamarra et al., 2006; ~es et al., 2004). Simo Bonaccorsi et al. (2009), Dugo et al. (2010) and Frizzo et al. (2004) characterized the chemical composition of the Citrus deliciosa Tenore essential oil obtained by cold pressing. The mandarin essential oil is a mixture of terpenes and their oxygenated derivatives. The volatile fraction of the mandarin oil obtained by cold pressing is between 96 and 98% of the whole oil. The essential oil has, as main compounds, D-limonene, g-terpinene, linalool, citral, mircene, among others (Bonaccorsi et al., 2009; Favretto et al., 1999; Teixeira et al., 2013). The major compound is the D-limonene, with a percentage of 60e98% m/m of the essential oil present in the peel. The other compounds, as g-terpinene, a-pinene, sabinene, mircene, linalol, are present in variable quantities, depending of the harvest, time of the year, location, among other factors (Castro and Escobar, 2014; Favretto et al., 1999; Lota et al., 2014;
http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011 0260-8774/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
2
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
~es et al., 2004). Simo The aldehydes, alcohols and ketones that generally appear as minority compounds or as traces are important in the composition of the oil's flavor, being products of high value when compared to the other terpenes that form the mixture. Its applications go from food industry to cosmetics and pharmaceutical industry (Bonaccorsi et al., 2009; Stücker et al., 2011; Teixeira et al., 2013). Between these compounds, there is methyl-N-methyl anthranilate, a compound used as a flavoring agent and construction block in organic chemistry (Opdyke, 1970). Another compound of interest by the industry is the aldehyde a-sinensal, used in cosmetics, perfume and in food industry (Smith et al., 2005). Most terpenes are thermally unstable, decomposing or oxidizing ~ es et al., in high temperatures or in presence of light or oxygen (Simo 2004). The fractional distillation is a unit operation that aims the separation of two or more substances by the volatility difference between them. This process depends of the pressure and temperature of the system, as well the physical and chemical characteristics of the components to be separated (Foust et al., 1982). The literature is scarce about using the vacuum fractional distillation for to separate essential oil components. Farah et al. (2006) reports the use of the fractional distillation to separate components of Myrtus communis L., with interesting results. Although, vacuum was not applied (Farah et al., 2006). CastiloHerrera et al. (2007) reported the use of fractional distillation during the hydrodistillation process to obtain Lippia graveolens H.B.K essential oil and to improve the phenolic fraction. The distillation column was placed between the distillation flask and the Clevenger apparatus. The author also reports the phenolic fraction improved due to the fractional distillation (Castilo-Herrera et al., 2007). One of the objectives of the vacuum fractional distillation is to verify a possible reduction of the degradation of the components of the essential oil by the high temperature, problem also found in the extraction with water vapor (drag with vapor) and in the hydrodistillation (Soto et al., 2014; Favretto et al., 1999). The objective of this work is to evaluate the use of the vacuum fractional distillation to separate some compounds of the green mandarin (C. deliciosa Tenore) essential oil, in addition to verify the effect of the pressure reduction in the boiling temperature of the mixture (raw essential oil). 2. Material and methods 2.1. Obtainment of essential oil The green mandarin (C. deliciosa Tenore) essential oil was obtained by cold pressing of the peels, provided by EcoCitrus, located in the city of Montenegro, in the state of Rio Grande do Sul, Brazil. The oil was produced in October of 2013, remaining stored in amber bottle, closed, in cold chamber (temperature between 1 and 6 C). 2.2. Description of the distillation system The fractionating system consisted of a glass column packed with Raschig rings with 8 mm of diameter (packing height of 8 cm), in three stages. The column and extract gathering system were coupled to a vacuum pump. The pump had a relief valve to adjust the vacuum of the system. An analogic vacuum gauge, localized in the top of the column, measured the internal pressure thereof. Between each stage, electronic valves (solenoids) and PT-100 performed the gathering of the samples and measured the vapor temperature, respectively. The solenoid valves, controlled by the PLC, directed the vapor of each stage to the condenser, which was
kept at 2e5 C, using ice packs. The system and its instrumentation was controlled by a PLC Altus FBs-24MA (14 digital entrances and 10 digital exits) and by a computer through the software Winproladder, aiming to automatize the system. 2.3. Fractionating tests Initially, it was tried to check the separation level of the mixture compounds in function of the distillation time and the boiling temperature in the bottom of the column (flask), keeping the vacuum in a constant value of 10 kPa. For this, distillation tests were performed, gathering only vapor of the top of the column, with collection time of 10 min, collecting part of the distillate for analysis and discarding the remaining. It was utilized 120 mL of raw essential oil in each batch. The distillation was performed until the volume of liquid in the flask reduced to near 10 mL. The collected samples were sent to GC/MS analysis. After, it searched to verify the distillate composition in function of the quantity of stages the vapor passed. The column operated under vacuum (10 kPa) until the vapor reached the top of it. The boiling temperature of the oil at this pressure was between 80 and 90 C. Then, the solenoid valves were opened and the vapor in each stage was gathered until the volume in the distillation flask reduced to the minimum possible, aiming to obtain circa 25 mL of extract to each stage (and the minimum possible volume to the bottom product), independently of the time necessary. The collected vapor was condensed in cooled bottles (2e5 C), and the vapor temperature was also monitored. The obtained samples were sent to GC/ MS analysis. 2.4. Chromatographic analysis The equipment used for the analysis as a gas chromatograph Hewlett Packard, model 6890 Series, equipped with a data processor HP-Chemstation and using a HP Innowax column (30 m 320 mm i.d.) with film thickness of 0,5 mm and a mass spectrometer Hewlett Packard, model MSD5973, equipped with a software HP Chemstation and Wiley 275 spectral library, using a capillary column of fused silica HP-Innowax (30 m 250 mm) with film thickness of 0,5 mm. The GC analysis was performed with column temperature of 40 C (8 min) to 180 C at 3 C/min, 180e230/C at 20 C/min and at 230 C for 20 min. Injector temperature was 250 C; split ratio of 1:50, ionization detector by flame with temperature of 250 C; using hydrogen as carrier gas with flux of 1,0 mL/min, at 34 kPa. For the quantification of the chemical compounds, it was utilized an internal standard of 1-octanol at 30,22 g/mL (25 mL), mixed with hexane (75 mL) and with the sample to be analyzed (10 mL). The used volume for injection in the GC/MS was 1,0 mL. The MS analysis was performed in a gas chromatograph coupled to a selective mass detector, as specified before. The used temperature program was the same as of the GC; interface of 280 C; split ratio of 1:100, using helium as carrier gas at 56 kPa. The gas flux was kept at 1,0 mL/min; ionization energy of 70 eV; the injected volume was 1 mL of sample, diluted in hexane (1:10). 3. Results and discussion 3.1. Results of the fractionating tests The raw oil was analyzed to characterize it. Limonene and gterpinene were the major compounds. This is a common chemotype in the C. deliciosa Tenore essential oil (Dugo et al., 2010) (Table 1). Through the distillation tests with removing only the top
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
3
Table 1 Composition (in mass fraction) of the mandarin essential oil obtained by cold pressing. The results obtained are compared to the ones presented by Bonaccorsi et al. (2009); Frizzo et al. (2004) and Dugo et al. (2010). Compound
This work
Bonaccorsi et al. (2009)
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
0,024 0,009 0,017 0,003 0,017 0,004 0,705 0,001 0,195 0,003 0,008 0,002 0,001 0,002 0,001 0,004 0,001 0,004
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpinene Linalool b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal a b c
a
Frizzo et al. (2004)
b
0,007 0,003 0,009 0,001 0,015 0,008 0,728 e 0,180 e e 0,002 0,001 0,004 0,005 0,007 0,002 0,006
Dugo et al. (2010)
c
0,019 0,006 0,013 0,002 0,014 0,003 0,727 0,001 0,184 0,004 0,006 0,001 0,001 0,002 0,001 0,006 0,001 0,003
The average value was considered. The value for cold pressed Cai mandarin were considered, in the month of March (the nearest month to October, the month the oil for this work was obtained). The corrected average of the peak areas was considered.
the top product, with exception of the mircene, who stayed in the flask (although the mass fraction was very low). However, the distillation time, as well as the batch regime can cause differences between the results (Nadais and Bernardo-Gil, 1993). It is observed again the separation in terpenes and other chemical classes, due to the physical and chemical properties of the compounds in the same class be similar. In qualitative level, it was not observed great deviations in relation to the prior tests, occurring a large presence of limonene and g-terpinene in the bottoms products (Table 3). Beyond individual analysis, it was also aimed to observe the composition of the fractions in terms of chemical functions to both
product (in intervals of 10 min between each sample collecting) and the bottoms (at the end of the batch), it was capable to make a qualitative analysis of the more volatile compounds and of the products that stayed in the distillation flask. This was done to determine which compounds left the mixture first and what of them were fixed. The quantitative and qualitative evaluation aimed to verify the degree of separation in each distillate and its relation with the raw essential oil (Table 2). In relation to distillates gathered by column stage, the degree of separation is similar to the separation obtained by collecting only the top product. It is observed that the qualitative separation of the compounds by stages is similar to the distillation tests removing
Table 2 Average mass fractionsa of the compounds in the raw oil, distillates and in the flask obtained in the distillation tests collecting only the top of the column and analyzed by GC/ MS. The grouping of the compounds in chemical classes is also presented. Bottom
Mass in bottom (g)
Recovery (%)b
e e 0,004 e 0,005 0,002 0,684 0,002 0,279 0,009 0,012 0,003 e e e e e e
e e e e e e 0,201 e 0,217 0,003 0,027 0,013 0,059 0,085 0,085 0,170 0,028 0,114
e e e e e e 0,718 e 0,775 0,011 0,096 0,046 0,214 0,303 0,303 0,607 0,100 0,407
e e e e e e 1,00 e 3,91 1,17 13,50 22,75 99,75 99,17 99,17 99,17 98,00 99,75
0,997 0,003 e e e
0,59 0,098 0,028 0,114 0,170
2,106 0,350 0,100 0,407 0,607
2,10 68,60 98,00 99,75 99,17
Compound
Raw oil
Mass in raw oil (g)
Distillate 1
2
3
4
5
6
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
1,938 0,714 1,428 0,204 1,632 0,204 72,114 0,204 19,788 0,918 0,714 0,204 0,204 0,306 0,306 0,612 0,102 0,408
0,108 0,046 0,036 0,019 0,037 0,200 0,418 0,041 0,089 0,004 0,002 e e e e e e e
0,028 0,009 0,031 0,005 0,032 0,005 0,760 0,002 0,119 0,006 0,003 e e e e e e e
0,007 0,002 0,013 0,003 0,020 0,005 0,785 0,002 0,152 0,007 0,004 e e e e e e e
0,004 e 0,007 e 0,013 0,004 0,759 0,002 0,195 0,007 0,007 0,002 e e e e e e
e e 0,003 e 0,008 0,003 0,748 0,002 0,218 0,008 0,008 0,002 e e e e e e
0,984 0,005 0,001 0,004 0,006
100,368 0,510 0,102 0,408 0,612
1,000 e e e e
1,000 e e e e
1,000 e e e e
0,998 0,002 e e e
0,998 0,002 e e e
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpineno Linalool b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal Chemical classes Hydrocarbon terpene Alcohol Phenol Aldehyde Amine/ether a b
The marker ‘e’ indicates absence of the substance in the fraction. Of the bottom relative to the raw oil.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
4
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
Table 3 Average mass fractionsa obtained in each of the stages of the column.
Compound
Raw oil
Mass in raw oil (g)
Top
Average mass fraction Second stage First stage
Bottom
Mass in bottom (g)
Recovery (%)
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
1,938 0,714 1,428 0,204 1,632 0,204 72,114 0,204 19,788 0,918 0,714 0,204 0,204 0,306 0,306 0,612 0,102 0,408
0,037 0,013 0,033 0,006 0,032 0,005 0,753 0,002 0,110 0,006 0,003 e e e e e e e
0,005 0,003 0,011 0,002 0,018 0,004 0,771 0,002 0,172 0,006 0,006 e e e e e e e
e e 0,005 e 0,008 0,003 0,706 0,002 0,256 0,005 0,012 0,003 e e e e e e
e e e e 0,003 e 0,380 0,001 0,284 0,004 0,023 0,011 0,031 0,031 0,052 0,101 0,017 0,062
e e e e 0,019 e 2,384 0,006 1,811 0,026 0,147 0,070 0,198 0,306 0,306 0,606 0,102 0,395
e e e e 1,17 e 3,31 3,13 9,15 2,78 20,54 34,38 96,88 100,00 100,00 98,96 100,00 96,88
0,984 0,005 0,001 0,004 0,006
100,368 0,510 0,102 0,408 0,612
1,000 e e e e
1,000 e e e e
0,997 0,003 e e e
0,778 0,042 0,017 0,062 0,101
4,896 0,376 0,102 0,395 0,606
4,88 73,75 100,00 96,88 98,96
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpineno Linalol b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal Chemical classes Hydrocarbon terpene Alcohol Phenol Aldehyde Amine/ether a
The marker ‘e’ indicates absence of the substance in the fraction.
tests and what would be the separation pattern. As noted earlier, is visible the separation of the oil in hydrocarbon terpenes and in the other chemical functions which, due to intermolecular interactions, tend to have higher boiling points (Soto et al., 2014), staying in the distillation flask. It is remarkable that, both in the first distillations than in the superior stages, the distillates were composed exclusively by hydrocarbon terpenes. The only chemical function that was detected outside the bottoms product was the alcohol function (linalool), being detected in the final stages of the separation process. The main difference between the raw oil and the distillates was the visual appearance. The raw oil extracted by pressing has a dark green coloration, characteristic of the fruit's peel. The distillate is colorless, presenting no visual relation to the oil of origin. The bottom product, due to the increase in the concentration of colored compounds and due to the temperature, has a dark color and a high viscosity. The visual appearance gives to the distilled oil a better applicability in the industry, because it prevents an unwanted coloration of the products who use the oil as a raw material (Gamarra et al., 2006). In sensory context, the distillates present a considerably different aroma compared to the raw oil, while the bottom product has a very sharp odor (Oliveira et al., 2011; Stücker et al., 2011). The presence of aldehydes, alcohols and phenols in the bottoms products, compounds who are responsible to the nuance of the raw oil aroma, ends to sharp the aroma of the concentrated product in the flask. This concentrated product, due to its composition, is of the interest of the industry, despite its color, which, depending on its application, must be removed (Favretto et al., 1999; Gamarra ~es et al., 2004). et al., 2006; Simo Among the compounds who stayed in the flask, it was observed that the mass fractions of some of them were increased up to 25 times in relation to the mass fraction in the raw essential oil, indicating the potentialities of the process (Table 4). Among these compounds, it is remarkable an increase of the mass fraction of the methyl-N-methyl anthranilate, thymol and a-sinensal, when compared to the raw oil. Despite of the large increase in the mass fraction, the concentration effect can provoke interpretation errors,
as we can see the recovery of linalool was poor (22,75%) when compared to the other compounds, with recoveries greater than 95%.
3.2. Evaluation of the oil thermal stability Both distillates and bottom products were analyzed by GC/MS. None of the distillates presented evidences of thermal degradation nor oxidation of its compounds when compared to the raw oil, with no different compound appeared in these fractions. The bottom products, when analyzed by MS, also did not present oxidation and decomposition evidences. Oxides of limonene and terpinene were detected in considerably low concentrations (mass fraction lesser than 0,01) in some bottom products. In these products, it was observed the appearing of these substances, which were not detected by the GC/MS analysis in the raw oil, neither in the tests of gathering top product (Table 5). The low mass fraction of these compounds can indicate a small degradation of the oil, or can be trace compounds, which, due to the low concentration, could not be detected in the raw oil. Bonaccorsi et al. (2009) and Dugo et al. (2010) report these compounds as trace compounds in cold pressed mandarin peel oil. Librando and Tringali (2005), in a work regarding the oxidation of a-pinene, presents the role of ozone, hydroxyl radical and UV light in the oxidation of terpenes, more than moderate heating. The concentration of the bottom product by removing the light terpenes, decreasing more than 90% of the initial volume of the raw oil, allows that trace compounds, before undetectable by the GC/MS, could be detected, making it difficult to analyze the results (Favretto et al., 1999; Lota et al., 2014; Stücker et al., 2011). It is more probable that these compounds were already in the raw oil as trace compounds than being products of the exposition of the raw oil to heat and oxygen during the operation of the column. If degradation exists, it is very low, not harming the quality of the products obtained by vacuum fractional distillation.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
5
Table 4 Comparison between the mass fraction of some compounds in the bottom product compared to the raw essential oil. Substance
Average mass fraction (raw Mass in raw oil oil) (g)
Average mass fraction (bottom)
Mass in bottom (g)
Relative increase to the raw oil (times)
Recovery (%)
Methyl-N-methyl anthranilate a-Sinensal Thymol Linalool a-Terpineol
0,006
0,612
0,170
0,607
28,33
99,17
0,004 0,001 0,002 0,003
0,408 0,102 0,204 0,306
0,114 0,028 0,013 0,085
0,407 0,100 0,046 0,303
28,50 28,00 6,50 28,33
99,75 98,00 22,75 99,17
Table 5 Summary of the compounds detected in the GC/MS analysis of the bottom products and were not detected in the raw oil. Substance
Average mass fraction (bottom)
Mass (g)
Chemical class
Possible origin
Terpinen-4-ol Perillaldehyde Trans-carveol Cis-b-terpineol a-Caryophylene
0,005 0,008 0,004 0,003 0,003
0,018 0,029 0,014 0,011 0,011
aliphatic alcohol aldehyde aliphatic alcohol aliphatic alcohol sesquiterpene
isomerization of a-terpineol oxidation of limonene oxidation of limonene isomerization of a-terpineol isomerization of b-caryophylene
4. Conclusions We observed that the vacuum fractional distillation is effective to separate between chemical classes. The hydrocarbon terpenes were separated from the ketones, alcohols and aldehydes and these remained in the distillation flask. The equipment was not able to separate efficiently the terpenes between them without the use of more stages, but the separation between chemical classes is of interest of the industry. The column's pressure influenced in an important way the boiling point of the essential oil, from near 180 C at 100 kPa (room pressure) to 80e90 C at 10 kPa (maximum vacuum of the column). There was no evidence of degradation of the distillates. In the bottoms, it was observed the appearing of compounds that probable are traces and, because of the reduction of the volume of oil, could be detected; or they can also be arising from oxidation processes. However, this degradation (if exists) did not reduce the quality of the obtained products, both the distillates as the bottoms. It was observed a considerable increase of the concentration of some interest compounds in the bottoms products, with relative increases in the mass fraction (compared to the raw oil) of more than 25 times in some of these compounds. However, the recovery varies for each compound. Acknowledgments The authors thank EcoCitrus for providing the essential oil and the Secretariat of Science and Technological Innovation of the state of Rio Grande do Sul by the incentive and the financing of the equipment, both of them giving support to the achievement of this research. References Bonaccorsi, I.L., et al., 2009. Characterization of mandarin (Citrus deliciosa Ten.) essential oil. Determination of volatiles, non-volatiles, physico-chemical indices and enantiomeric ratios. Nat. Product. Commun. 4 (11), 1595e1600. Castilo-Herrera, G.A., et al., 2007. Extraction method that enriches phenolic content
in oregano (Lippia graveloens H.B.K.) essential oil. J. Food Process Eng. 30, 661e669. Castro, M.D.L., Escobar, C.A.L., 2014. Towards a comprehensive exploitation of citrus. Trends Food Sci. Technol. xx, 1e13. n de productos naturales obtenidos de especies de Dellacassa, E., 2010. Normalizacio tica latinoamericana: proyecto CYTED IV.20. EDIPUCRS, Porto la flora aroma Alegre (org.). Dugo, P., et al., 2010. Analytical characterization of mandarin (Citrus deliciosa Ten.) essential oil. Flavour Fragr. J. 21, 34e46. Embrapa, 2004. Citrus map in the RS. Cultiv. HF 08e09. Farah, A., et al., 2006. Fractional distillation effect on the chemical composition of Moroccan myrtle (Myrtus communis L.) essential oils. Flavour Fragr. J. 21, 351e354. Favretto, L., et al., 1999. Chemometric analysis and extraction processes of mandarin essential oils. Anal. Chim. Acta 312, 199e205. Foust, A.S., et al., 1982. Principles of Unit Operations, second ed. Guanabara Dois, Rio de Janeiro. Frizzo, C.D., et al., 2004. Composition and seasonal variation of the essential oils from two mandarin cultivars of Southern Brazil. J. Agric. Food Chem. 52, 3036e3041. Gamarra, F.M.C., et al., 2006. Influence on the quality of essential lemon (Citrus aurantifolia) oil by distillation process. Braz. J. Chem. Eng. 23 (1), 147e151. Librando, V., Tringali, G., 2005. Atmospheric fate of OH initiated oxidation of terpenes. Reaction mechanism of a-pinene degradation and secondary organic aerosol formation. J. Environ. Manag. 75, 275e282. Lohbauer, C., 2014. Citrus Panorama in World. Available in: http://www.citrusbr. com.br. Accessed in Aug. 28, 2014. Lota, M.L., et al., 2014. Chemical variability of peel and leaf essential oils of mandarins from Citrus reticulata Blanco. Biochem. Syst. Ecol. 28, 61e78. Nadais, M.H., Bernardo-Gil, M.G., 1993. Vapour-liquid equilibria of apinene þ limonene at reduced pressures. Fluid Phase Equilib. 91, 312e330. Oliveira, J.V., et al., 2011. Fractionation of citronella (Cymbopogon winterianus) essential oil and concentrated orange oil phase by batch vacuum distillation. J. Food Eng. 102, 348e354. Opdyke, D.L.J., 1970. Metyhl-N-methyl Anthranilate. Fragrance Raw Materials Monographs, pp. 791e792. ~ es, C.M.O., et al., 2004. Farmacognosia: da planta ao medicamento, 5ª ed. Simo polis (org.). Editora UFRGS/Editora da UFSC, Porto Alegre/Floriano Smith, R.L., et al., 2005. A procedure for the safety evaluation of natural flavor complexes used as ingredients in food: essential oils. Food Chem. Toxicol. 43, 345e363. Soto, A., et al., 2014. Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids. Fluid Phase Equilib. 361, 37e44. ~o fracionada (DF) para obtença ~o de proStücker, C.Z., et al., 2011. Uso de destilaça leos essenciais de cítricos. In: dutos diferenciados em perfumaria a partir de o ~o da Sociedade Brasileira de Química, Floriano polis, SC. Reunia ~o. Teixeira, D.M.A., et al., 2013. Oleos essenciais aplicados em alimentos: uma revisa Rev. Bras. Pesqui. em Aliment. 4 (2), 69e81.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
Contents lists available at ScienceDirect
Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation W.P. Silvestre a, c, *, F. Agostini b, L.A.R. Muniz a, G.F. Pauletti c a
Course of Chemical Engineering, Center of Exact Sciences and Technology, University of Caxias do Sul (UCS), Brazil Institute of Biotechnology, University of Caxias do Sul, Brazil c Course of Agronomy, Center of Biological and Health Sciences, University of Caxias do Sul, Brazil b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 August 2015 Received in revised form 29 December 2015 Accepted 14 January 2016 Available online xxx
This work aims to evaluate the technical viability of vacuum fractional distillation to separate the components of green mandarin (Citrus deliciosa Tenore) essential oil. Thermal degradation was also analyzed. The obtained results demonstrate that vacuum fractional distillation is capable to separate the hydrocarbon terpenes, which were removed from the top/stages of the column, from the terpenes with other chemical functions, which remained in the bottom. Some trace compounds, such as methyl-Nmethyl anthranilate (mass fraction of 0,006 in the raw oil) and alpha sinensal (mass fraction of 0,004 in the raw oil), had their concentrations increased more than ten times after the separation, to mass fraction of 0,153 and 0,109, respectively. The mass fraction of the major compound of the essential oil, Dlimonene, was reduced from 0,707 in the raw oil, to 0,218 in the bottom. There was no evidence of thermal degradation in the products of the separation. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Fractioning column Green mandarin essential oil Terpenes Vacuum distillation GC/MS
1. Introduction The harvest of citrus fruits presents great importance worldwide, as its production, in 2013, was approximately 111,5 millions of tons. The main citrus fruits are orange, lemon, mandarin and lime, which have a high commercial value as sell ‘in nature’ or as a raw material for food industry (Castro and Escobar, 2014). The peel and the bagasse of citrus represent 40e50% of total weight of the fruit and in general are waste of the processing of this raw material, being both used as biomass. The bagasse is also used as component in animal feeding. The peel has many bioactive components, as ascorbic acid, terpenes and flavonoids, which can be extracted and after purified for various applications (Castro and Escobar, 2014; Lohbauer, 2014). The citrus essential oil is a mixture of terpenes, many of them with important industrial applications, in medicine, pharmacology, cosmetics and food industry (Bonaccorsi et al., 2009). Tough, to have a practical application for the minority compounds (which, in general, have more value), it is necessary to properly separate the
* Corresponding author. Laboratory of Chemistry and Soil Fertility, University of polis, 95074-270, Caxias do Caxias do Sul, Road Francisco Getúlio Vargas, 1135, Petro Sul, RS, Brazil. E-mail address: [email protected] (W.P. Silvestre).
mixture of substances in the raw oil (Castro and Escobar, 2014; ~es et al., 2004). Embrapa, 2004; Simo The genetics of the plant determines its chemotype. However, the environmental conditions (climate, soil type, presence of nutrients) are capable of provoke considerable variations in the oil and in the very chemotype, featuring an ‘ecotype’ (Dellacassa, 2010). Is also important highlight that the composition of the essential oil obtained varies considerably between the parts of the plant, as well by the extractive process (Gamarra et al., 2006; ~es et al., 2004). Simo Bonaccorsi et al. (2009), Dugo et al. (2010) and Frizzo et al. (2004) characterized the chemical composition of the Citrus deliciosa Tenore essential oil obtained by cold pressing. The mandarin essential oil is a mixture of terpenes and their oxygenated derivatives. The volatile fraction of the mandarin oil obtained by cold pressing is between 96 and 98% of the whole oil. The essential oil has, as main compounds, D-limonene, g-terpinene, linalool, citral, mircene, among others (Bonaccorsi et al., 2009; Favretto et al., 1999; Teixeira et al., 2013). The major compound is the D-limonene, with a percentage of 60e98% m/m of the essential oil present in the peel. The other compounds, as g-terpinene, a-pinene, sabinene, mircene, linalol, are present in variable quantities, depending of the harvest, time of the year, location, among other factors (Castro and Escobar, 2014; Favretto et al., 1999; Lota et al., 2014;
http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011 0260-8774/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
2
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
~es et al., 2004). Simo The aldehydes, alcohols and ketones that generally appear as minority compounds or as traces are important in the composition of the oil's flavor, being products of high value when compared to the other terpenes that form the mixture. Its applications go from food industry to cosmetics and pharmaceutical industry (Bonaccorsi et al., 2009; Stücker et al., 2011; Teixeira et al., 2013). Between these compounds, there is methyl-N-methyl anthranilate, a compound used as a flavoring agent and construction block in organic chemistry (Opdyke, 1970). Another compound of interest by the industry is the aldehyde a-sinensal, used in cosmetics, perfume and in food industry (Smith et al., 2005). Most terpenes are thermally unstable, decomposing or oxidizing ~ es et al., in high temperatures or in presence of light or oxygen (Simo 2004). The fractional distillation is a unit operation that aims the separation of two or more substances by the volatility difference between them. This process depends of the pressure and temperature of the system, as well the physical and chemical characteristics of the components to be separated (Foust et al., 1982). The literature is scarce about using the vacuum fractional distillation for to separate essential oil components. Farah et al. (2006) reports the use of the fractional distillation to separate components of Myrtus communis L., with interesting results. Although, vacuum was not applied (Farah et al., 2006). CastiloHerrera et al. (2007) reported the use of fractional distillation during the hydrodistillation process to obtain Lippia graveolens H.B.K essential oil and to improve the phenolic fraction. The distillation column was placed between the distillation flask and the Clevenger apparatus. The author also reports the phenolic fraction improved due to the fractional distillation (Castilo-Herrera et al., 2007). One of the objectives of the vacuum fractional distillation is to verify a possible reduction of the degradation of the components of the essential oil by the high temperature, problem also found in the extraction with water vapor (drag with vapor) and in the hydrodistillation (Soto et al., 2014; Favretto et al., 1999). The objective of this work is to evaluate the use of the vacuum fractional distillation to separate some compounds of the green mandarin (C. deliciosa Tenore) essential oil, in addition to verify the effect of the pressure reduction in the boiling temperature of the mixture (raw essential oil). 2. Material and methods 2.1. Obtainment of essential oil The green mandarin (C. deliciosa Tenore) essential oil was obtained by cold pressing of the peels, provided by EcoCitrus, located in the city of Montenegro, in the state of Rio Grande do Sul, Brazil. The oil was produced in October of 2013, remaining stored in amber bottle, closed, in cold chamber (temperature between 1 and 6 C). 2.2. Description of the distillation system The fractionating system consisted of a glass column packed with Raschig rings with 8 mm of diameter (packing height of 8 cm), in three stages. The column and extract gathering system were coupled to a vacuum pump. The pump had a relief valve to adjust the vacuum of the system. An analogic vacuum gauge, localized in the top of the column, measured the internal pressure thereof. Between each stage, electronic valves (solenoids) and PT-100 performed the gathering of the samples and measured the vapor temperature, respectively. The solenoid valves, controlled by the PLC, directed the vapor of each stage to the condenser, which was
kept at 2e5 C, using ice packs. The system and its instrumentation was controlled by a PLC Altus FBs-24MA (14 digital entrances and 10 digital exits) and by a computer through the software Winproladder, aiming to automatize the system. 2.3. Fractionating tests Initially, it was tried to check the separation level of the mixture compounds in function of the distillation time and the boiling temperature in the bottom of the column (flask), keeping the vacuum in a constant value of 10 kPa. For this, distillation tests were performed, gathering only vapor of the top of the column, with collection time of 10 min, collecting part of the distillate for analysis and discarding the remaining. It was utilized 120 mL of raw essential oil in each batch. The distillation was performed until the volume of liquid in the flask reduced to near 10 mL. The collected samples were sent to GC/MS analysis. After, it searched to verify the distillate composition in function of the quantity of stages the vapor passed. The column operated under vacuum (10 kPa) until the vapor reached the top of it. The boiling temperature of the oil at this pressure was between 80 and 90 C. Then, the solenoid valves were opened and the vapor in each stage was gathered until the volume in the distillation flask reduced to the minimum possible, aiming to obtain circa 25 mL of extract to each stage (and the minimum possible volume to the bottom product), independently of the time necessary. The collected vapor was condensed in cooled bottles (2e5 C), and the vapor temperature was also monitored. The obtained samples were sent to GC/ MS analysis. 2.4. Chromatographic analysis The equipment used for the analysis as a gas chromatograph Hewlett Packard, model 6890 Series, equipped with a data processor HP-Chemstation and using a HP Innowax column (30 m 320 mm i.d.) with film thickness of 0,5 mm and a mass spectrometer Hewlett Packard, model MSD5973, equipped with a software HP Chemstation and Wiley 275 spectral library, using a capillary column of fused silica HP-Innowax (30 m 250 mm) with film thickness of 0,5 mm. The GC analysis was performed with column temperature of 40 C (8 min) to 180 C at 3 C/min, 180e230/C at 20 C/min and at 230 C for 20 min. Injector temperature was 250 C; split ratio of 1:50, ionization detector by flame with temperature of 250 C; using hydrogen as carrier gas with flux of 1,0 mL/min, at 34 kPa. For the quantification of the chemical compounds, it was utilized an internal standard of 1-octanol at 30,22 g/mL (25 mL), mixed with hexane (75 mL) and with the sample to be analyzed (10 mL). The used volume for injection in the GC/MS was 1,0 mL. The MS analysis was performed in a gas chromatograph coupled to a selective mass detector, as specified before. The used temperature program was the same as of the GC; interface of 280 C; split ratio of 1:100, using helium as carrier gas at 56 kPa. The gas flux was kept at 1,0 mL/min; ionization energy of 70 eV; the injected volume was 1 mL of sample, diluted in hexane (1:10). 3. Results and discussion 3.1. Results of the fractionating tests The raw oil was analyzed to characterize it. Limonene and gterpinene were the major compounds. This is a common chemotype in the C. deliciosa Tenore essential oil (Dugo et al., 2010) (Table 1). Through the distillation tests with removing only the top
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
3
Table 1 Composition (in mass fraction) of the mandarin essential oil obtained by cold pressing. The results obtained are compared to the ones presented by Bonaccorsi et al. (2009); Frizzo et al. (2004) and Dugo et al. (2010). Compound
This work
Bonaccorsi et al. (2009)
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
0,024 0,009 0,017 0,003 0,017 0,004 0,705 0,001 0,195 0,003 0,008 0,002 0,001 0,002 0,001 0,004 0,001 0,004
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpinene Linalool b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal a b c
a
Frizzo et al. (2004)
b
0,007 0,003 0,009 0,001 0,015 0,008 0,728 e 0,180 e e 0,002 0,001 0,004 0,005 0,007 0,002 0,006
Dugo et al. (2010)
c
0,019 0,006 0,013 0,002 0,014 0,003 0,727 0,001 0,184 0,004 0,006 0,001 0,001 0,002 0,001 0,006 0,001 0,003
The average value was considered. The value for cold pressed Cai mandarin were considered, in the month of March (the nearest month to October, the month the oil for this work was obtained). The corrected average of the peak areas was considered.
the top product, with exception of the mircene, who stayed in the flask (although the mass fraction was very low). However, the distillation time, as well as the batch regime can cause differences between the results (Nadais and Bernardo-Gil, 1993). It is observed again the separation in terpenes and other chemical classes, due to the physical and chemical properties of the compounds in the same class be similar. In qualitative level, it was not observed great deviations in relation to the prior tests, occurring a large presence of limonene and g-terpinene in the bottoms products (Table 3). Beyond individual analysis, it was also aimed to observe the composition of the fractions in terms of chemical functions to both
product (in intervals of 10 min between each sample collecting) and the bottoms (at the end of the batch), it was capable to make a qualitative analysis of the more volatile compounds and of the products that stayed in the distillation flask. This was done to determine which compounds left the mixture first and what of them were fixed. The quantitative and qualitative evaluation aimed to verify the degree of separation in each distillate and its relation with the raw essential oil (Table 2). In relation to distillates gathered by column stage, the degree of separation is similar to the separation obtained by collecting only the top product. It is observed that the qualitative separation of the compounds by stages is similar to the distillation tests removing
Table 2 Average mass fractionsa of the compounds in the raw oil, distillates and in the flask obtained in the distillation tests collecting only the top of the column and analyzed by GC/ MS. The grouping of the compounds in chemical classes is also presented. Bottom
Mass in bottom (g)
Recovery (%)b
e e 0,004 e 0,005 0,002 0,684 0,002 0,279 0,009 0,012 0,003 e e e e e e
e e e e e e 0,201 e 0,217 0,003 0,027 0,013 0,059 0,085 0,085 0,170 0,028 0,114
e e e e e e 0,718 e 0,775 0,011 0,096 0,046 0,214 0,303 0,303 0,607 0,100 0,407
e e e e e e 1,00 e 3,91 1,17 13,50 22,75 99,75 99,17 99,17 99,17 98,00 99,75
0,997 0,003 e e e
0,59 0,098 0,028 0,114 0,170
2,106 0,350 0,100 0,407 0,607
2,10 68,60 98,00 99,75 99,17
Compound
Raw oil
Mass in raw oil (g)
Distillate 1
2
3
4
5
6
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
1,938 0,714 1,428 0,204 1,632 0,204 72,114 0,204 19,788 0,918 0,714 0,204 0,204 0,306 0,306 0,612 0,102 0,408
0,108 0,046 0,036 0,019 0,037 0,200 0,418 0,041 0,089 0,004 0,002 e e e e e e e
0,028 0,009 0,031 0,005 0,032 0,005 0,760 0,002 0,119 0,006 0,003 e e e e e e e
0,007 0,002 0,013 0,003 0,020 0,005 0,785 0,002 0,152 0,007 0,004 e e e e e e e
0,004 e 0,007 e 0,013 0,004 0,759 0,002 0,195 0,007 0,007 0,002 e e e e e e
e e 0,003 e 0,008 0,003 0,748 0,002 0,218 0,008 0,008 0,002 e e e e e e
0,984 0,005 0,001 0,004 0,006
100,368 0,510 0,102 0,408 0,612
1,000 e e e e
1,000 e e e e
1,000 e e e e
0,998 0,002 e e e
0,998 0,002 e e e
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpineno Linalool b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal Chemical classes Hydrocarbon terpene Alcohol Phenol Aldehyde Amine/ether a b
The marker ‘e’ indicates absence of the substance in the fraction. Of the bottom relative to the raw oil.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
4
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
Table 3 Average mass fractionsa obtained in each of the stages of the column.
Compound
Raw oil
Mass in raw oil (g)
Top
Average mass fraction Second stage First stage
Bottom
Mass in bottom (g)
Recovery (%)
a-Pinene a-Tujene b-Pinene
0,019 0,007 0,014 0,002 0,016 0,002 0,707 0,002 0,194 0,009 0,007 0,002 0,002 0,003 0,003 0,006 0,001 0,004
1,938 0,714 1,428 0,204 1,632 0,204 72,114 0,204 19,788 0,918 0,714 0,204 0,204 0,306 0,306 0,612 0,102 0,408
0,037 0,013 0,033 0,006 0,032 0,005 0,753 0,002 0,110 0,006 0,003 e e e e e e e
0,005 0,003 0,011 0,002 0,018 0,004 0,771 0,002 0,172 0,006 0,006 e e e e e e e
e e 0,005 e 0,008 0,003 0,706 0,002 0,256 0,005 0,012 0,003 e e e e e e
e e e e 0,003 e 0,380 0,001 0,284 0,004 0,023 0,011 0,031 0,031 0,052 0,101 0,017 0,062
e e e e 0,019 e 2,384 0,006 1,811 0,026 0,147 0,070 0,198 0,306 0,306 0,606 0,102 0,395
e e e e 1,17 e 3,31 3,13 9,15 2,78 20,54 34,38 96,88 100,00 100,00 98,96 100,00 96,88
0,984 0,005 0,001 0,004 0,006
100,368 0,510 0,102 0,408 0,612
1,000 e e e e
1,000 e e e e
0,997 0,003 e e e
0,778 0,042 0,017 0,062 0,101
4,896 0,376 0,102 0,395 0,606
4,88 73,75 100,00 96,88 98,96
Sabinene Mircene a-Terpinene Limonene b-Phellandrene g-Terpinene p-Cymene D-Terpineno Linalol b-Caryophylene a-Terpineol a-Farnesene Methyl-N-methyl anthranilate Thymol a-Sinensal Chemical classes Hydrocarbon terpene Alcohol Phenol Aldehyde Amine/ether a
The marker ‘e’ indicates absence of the substance in the fraction.
tests and what would be the separation pattern. As noted earlier, is visible the separation of the oil in hydrocarbon terpenes and in the other chemical functions which, due to intermolecular interactions, tend to have higher boiling points (Soto et al., 2014), staying in the distillation flask. It is remarkable that, both in the first distillations than in the superior stages, the distillates were composed exclusively by hydrocarbon terpenes. The only chemical function that was detected outside the bottoms product was the alcohol function (linalool), being detected in the final stages of the separation process. The main difference between the raw oil and the distillates was the visual appearance. The raw oil extracted by pressing has a dark green coloration, characteristic of the fruit's peel. The distillate is colorless, presenting no visual relation to the oil of origin. The bottom product, due to the increase in the concentration of colored compounds and due to the temperature, has a dark color and a high viscosity. The visual appearance gives to the distilled oil a better applicability in the industry, because it prevents an unwanted coloration of the products who use the oil as a raw material (Gamarra et al., 2006). In sensory context, the distillates present a considerably different aroma compared to the raw oil, while the bottom product has a very sharp odor (Oliveira et al., 2011; Stücker et al., 2011). The presence of aldehydes, alcohols and phenols in the bottoms products, compounds who are responsible to the nuance of the raw oil aroma, ends to sharp the aroma of the concentrated product in the flask. This concentrated product, due to its composition, is of the interest of the industry, despite its color, which, depending on its application, must be removed (Favretto et al., 1999; Gamarra ~es et al., 2004). et al., 2006; Simo Among the compounds who stayed in the flask, it was observed that the mass fractions of some of them were increased up to 25 times in relation to the mass fraction in the raw essential oil, indicating the potentialities of the process (Table 4). Among these compounds, it is remarkable an increase of the mass fraction of the methyl-N-methyl anthranilate, thymol and a-sinensal, when compared to the raw oil. Despite of the large increase in the mass fraction, the concentration effect can provoke interpretation errors,
as we can see the recovery of linalool was poor (22,75%) when compared to the other compounds, with recoveries greater than 95%.
3.2. Evaluation of the oil thermal stability Both distillates and bottom products were analyzed by GC/MS. None of the distillates presented evidences of thermal degradation nor oxidation of its compounds when compared to the raw oil, with no different compound appeared in these fractions. The bottom products, when analyzed by MS, also did not present oxidation and decomposition evidences. Oxides of limonene and terpinene were detected in considerably low concentrations (mass fraction lesser than 0,01) in some bottom products. In these products, it was observed the appearing of these substances, which were not detected by the GC/MS analysis in the raw oil, neither in the tests of gathering top product (Table 5). The low mass fraction of these compounds can indicate a small degradation of the oil, or can be trace compounds, which, due to the low concentration, could not be detected in the raw oil. Bonaccorsi et al. (2009) and Dugo et al. (2010) report these compounds as trace compounds in cold pressed mandarin peel oil. Librando and Tringali (2005), in a work regarding the oxidation of a-pinene, presents the role of ozone, hydroxyl radical and UV light in the oxidation of terpenes, more than moderate heating. The concentration of the bottom product by removing the light terpenes, decreasing more than 90% of the initial volume of the raw oil, allows that trace compounds, before undetectable by the GC/MS, could be detected, making it difficult to analyze the results (Favretto et al., 1999; Lota et al., 2014; Stücker et al., 2011). It is more probable that these compounds were already in the raw oil as trace compounds than being products of the exposition of the raw oil to heat and oxygen during the operation of the column. If degradation exists, it is very low, not harming the quality of the products obtained by vacuum fractional distillation.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011
W.P. Silvestre et al. / Journal of Food Engineering xxx (2016) 1e5
5
Table 4 Comparison between the mass fraction of some compounds in the bottom product compared to the raw essential oil. Substance
Average mass fraction (raw Mass in raw oil oil) (g)
Average mass fraction (bottom)
Mass in bottom (g)
Relative increase to the raw oil (times)
Recovery (%)
Methyl-N-methyl anthranilate a-Sinensal Thymol Linalool a-Terpineol
0,006
0,612
0,170
0,607
28,33
99,17
0,004 0,001 0,002 0,003
0,408 0,102 0,204 0,306
0,114 0,028 0,013 0,085
0,407 0,100 0,046 0,303
28,50 28,00 6,50 28,33
99,75 98,00 22,75 99,17
Table 5 Summary of the compounds detected in the GC/MS analysis of the bottom products and were not detected in the raw oil. Substance
Average mass fraction (bottom)
Mass (g)
Chemical class
Possible origin
Terpinen-4-ol Perillaldehyde Trans-carveol Cis-b-terpineol a-Caryophylene
0,005 0,008 0,004 0,003 0,003
0,018 0,029 0,014 0,011 0,011
aliphatic alcohol aldehyde aliphatic alcohol aliphatic alcohol sesquiterpene
isomerization of a-terpineol oxidation of limonene oxidation of limonene isomerization of a-terpineol isomerization of b-caryophylene
4. Conclusions We observed that the vacuum fractional distillation is effective to separate between chemical classes. The hydrocarbon terpenes were separated from the ketones, alcohols and aldehydes and these remained in the distillation flask. The equipment was not able to separate efficiently the terpenes between them without the use of more stages, but the separation between chemical classes is of interest of the industry. The column's pressure influenced in an important way the boiling point of the essential oil, from near 180 C at 100 kPa (room pressure) to 80e90 C at 10 kPa (maximum vacuum of the column). There was no evidence of degradation of the distillates. In the bottoms, it was observed the appearing of compounds that probable are traces and, because of the reduction of the volume of oil, could be detected; or they can also be arising from oxidation processes. However, this degradation (if exists) did not reduce the quality of the obtained products, both the distillates as the bottoms. It was observed a considerable increase of the concentration of some interest compounds in the bottoms products, with relative increases in the mass fraction (compared to the raw oil) of more than 25 times in some of these compounds. However, the recovery varies for each compound. Acknowledgments The authors thank EcoCitrus for providing the essential oil and the Secretariat of Science and Technological Innovation of the state of Rio Grande do Sul by the incentive and the financing of the equipment, both of them giving support to the achievement of this research. References Bonaccorsi, I.L., et al., 2009. Characterization of mandarin (Citrus deliciosa Ten.) essential oil. Determination of volatiles, non-volatiles, physico-chemical indices and enantiomeric ratios. Nat. Product. Commun. 4 (11), 1595e1600. Castilo-Herrera, G.A., et al., 2007. Extraction method that enriches phenolic content
in oregano (Lippia graveloens H.B.K.) essential oil. J. Food Process Eng. 30, 661e669. Castro, M.D.L., Escobar, C.A.L., 2014. Towards a comprehensive exploitation of citrus. Trends Food Sci. Technol. xx, 1e13. n de productos naturales obtenidos de especies de Dellacassa, E., 2010. Normalizacio tica latinoamericana: proyecto CYTED IV.20. EDIPUCRS, Porto la flora aroma Alegre (org.). Dugo, P., et al., 2010. Analytical characterization of mandarin (Citrus deliciosa Ten.) essential oil. Flavour Fragr. J. 21, 34e46. Embrapa, 2004. Citrus map in the RS. Cultiv. HF 08e09. Farah, A., et al., 2006. Fractional distillation effect on the chemical composition of Moroccan myrtle (Myrtus communis L.) essential oils. Flavour Fragr. J. 21, 351e354. Favretto, L., et al., 1999. Chemometric analysis and extraction processes of mandarin essential oils. Anal. Chim. Acta 312, 199e205. Foust, A.S., et al., 1982. Principles of Unit Operations, second ed. Guanabara Dois, Rio de Janeiro. Frizzo, C.D., et al., 2004. Composition and seasonal variation of the essential oils from two mandarin cultivars of Southern Brazil. J. Agric. Food Chem. 52, 3036e3041. Gamarra, F.M.C., et al., 2006. Influence on the quality of essential lemon (Citrus aurantifolia) oil by distillation process. Braz. J. Chem. Eng. 23 (1), 147e151. Librando, V., Tringali, G., 2005. Atmospheric fate of OH initiated oxidation of terpenes. Reaction mechanism of a-pinene degradation and secondary organic aerosol formation. J. Environ. Manag. 75, 275e282. Lohbauer, C., 2014. Citrus Panorama in World. Available in: http://www.citrusbr. com.br. Accessed in Aug. 28, 2014. Lota, M.L., et al., 2014. Chemical variability of peel and leaf essential oils of mandarins from Citrus reticulata Blanco. Biochem. Syst. Ecol. 28, 61e78. Nadais, M.H., Bernardo-Gil, M.G., 1993. Vapour-liquid equilibria of apinene þ limonene at reduced pressures. Fluid Phase Equilib. 91, 312e330. Oliveira, J.V., et al., 2011. Fractionation of citronella (Cymbopogon winterianus) essential oil and concentrated orange oil phase by batch vacuum distillation. J. Food Eng. 102, 348e354. Opdyke, D.L.J., 1970. Metyhl-N-methyl Anthranilate. Fragrance Raw Materials Monographs, pp. 791e792. ~ es, C.M.O., et al., 2004. Farmacognosia: da planta ao medicamento, 5ª ed. Simo polis (org.). Editora UFRGS/Editora da UFSC, Porto Alegre/Floriano Smith, R.L., et al., 2005. A procedure for the safety evaluation of natural flavor complexes used as ingredients in food: essential oils. Food Chem. Toxicol. 43, 345e363. Soto, A., et al., 2014. Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids. Fluid Phase Equilib. 361, 37e44. ~o fracionada (DF) para obtença ~o de proStücker, C.Z., et al., 2011. Uso de destilaça leos essenciais de cítricos. In: dutos diferenciados em perfumaria a partir de o ~o da Sociedade Brasileira de Química, Floriano polis, SC. Reunia ~o. Teixeira, D.M.A., et al., 2013. Oleos essenciais aplicados em alimentos: uma revisa Rev. Bras. Pesqui. em Aliment. 4 (2), 69e81.
Please cite this article in press as: Silvestre, W.P., et al., Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation, Journal of Food Engineering (2016), http://dx.doi.org/10.1016/j.jfoodeng.2016.01.011