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Molecules 2019, 24(4), 764; https://doi.org/10.3390/molecules24040764

Article
HS-SPME Analysis of True Lavender (Lavandula angustifolia Mill.) Leaves Treated by Various Drying Methods
1
Faculty of Biotechnology and Food Science, Wrocław University of Environmental and Life Sciences, Norwida 25, 50-375 Wrocław, Poland
2
Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, Chełmońskiego 37-41, 51-630 Wrocław, Poland
*
Author to whom correspondence should be addressed.
Academic Editor: Constantinos K. Zacharis
Received: 31 January 2019 / Accepted: 18 February 2019 / Published: 20 February 2019

Abstract

:
True lavender (Lavandula angustifolia Mill.) is a widely used flavoring and medicinal plant, which strong aroma is mainly composed of linalool and linalyl acetate. The most valuable parts of the plant are the flowers, however leaves are also abundant in volatile constituents. One of the main factors responsible for its quality is the preservation procedure, which usually comes down to a drying process. For this reason an attempt to verify the influence of various drying methods (convective drying, vacuum-microwave drying and combined convection pre-drying with vacuum-microwave finishing drying) on the quality of true lavender leaves was carried out by determination of the volatile constituents profile by solid-phase microextraction (SPME) coupled with GC-MS technique. Total essential oil (EO) content was also verified. The study has revealed that the optimal drying method is strongly dependent on the purpose of the product. For flavoring properties convective drying at 60 °C is the most optimal method, while the best for preserving the highest amount of EO is vacuum-microwave drying at 480 W. Furthermore, SPME analysis had shown that drying may increase the value of true lavender leaves by significantly affecting the linalool to linalyl acetate to camphor ratio in the volatile profile.
Keywords:
essential oil; drying; SPME; true lavender; volatile constituents

1. Introduction

Lavandula angustifolia Mill. (also named Lavandula officinalis Chaix)—the true lavender—is a essential oil-bearing plant known worldwide, which history of usage starts in Greek and Roman times and last up to this day. The entire genus belongs to the large Lamiacae family, which is mostly native to the Mediterranean region, however true lavender is a commonly growing plant in England, Europe, North America and Australia. The most valuable part of the plant are flowers due to their much higher essential oil content than leaves, and a favorable linalool to linalyl aceate to camphor ratio [1].
Nowadays due to the well-recognizable aroma lavender plants or their derivatives find applications in numerous ways, like in perfumery, cosmetics and household products, antimicrobial agents, food fragrance and flavor improvement or as food preservatives [1,2,3]. Furthermore, the essential oil obtained from lavender is an interesting object for trials considering biological activity and even in medicinal trials. Some studies and overviews from recent years mention the anti-aging, analgesic, nuroprotective, sedative or anticancer activities of lavender essential oil [2,3,4,5,6,7,8,9]. These various lavender essential oil applications are due to their unique chemical composition, rich in monoterpenes, sesquiterpenes, sesquiterpenoids, aliphatic compounds and especially an abundance of monoterpenoids [10], with linalool and linalyl acetate highlighted as main flower components [1,11,12]. In the case of the leaves the main essential oil constituents are eucalyptol (1,8-cineole), camphor and borneol [13,14,15].
As the main factors affecting the quality of the essential oils obtained from essential oils-bearing plants, plant chemotype, growing conditions and location, fertilizers used, time of harvesting and post-harvest treatment (including preservation method) are mentioned [2,11]. Among those factors, the preservation method has the most significant influence, where the most common one for plants rich in essential oils is drying [16,17,18]. Drying of essential oil-bearing plants allows one to obtain sustainable products with guaranteed quality, although it may cause also considerable losses of valuable constituents—mainly affecting the volatile constituents [17]. Furthermore, the color of the raw material may be strongly influenced by drying [16].
The traditional and natural method of drying uses solar radiation, however nowadays convective drying (CD), which uses flows of the hot air [17,18], is the most common drying method used in natural products treatment. Nevertheless other techniques like freeze-drying, infrared drying, vacuum-microwave drying (VMD), spray drying or a combination of convective pre-drying with vacuum-microwave finishing drying (CPD-VMFD) are lately the objects of numerous investigations regarding natural products drying [18]. Unfortunately in case of drying the true lavender leaves only single factors were investigated. Interest in this topic is due to the necessity to find an optimal drying method for specific raw materials. In addition, not only a specific technique, but also its parameters, like drying time, temperature or pressure have a significant influence on the quality of the obtained products [19,20,21,22]. Overall the most important are air velocity and temperature—for plants the most suitable temperature is one between 50 °C and 60 °C [16].
The objective of this study was to determine the volatile profile composition and compound quantity of true lavender leaves and the influence of three drying methods (CD, VMD, CPD-VMFD) applied with various parameters. The study was done by a solid-phase microextraction (SPME) coupled with gas chromatography mass spectrometry technique (GC-MS). Also the total essential oil content was validated by using a hydrodistillation extraction technique.

2. Results and Discussion

2.1. Drying Kinetics

Figure 1 shows changes with time of the moisture ratio (MR) of leaf samples dehydrated by VMD at three magnetron powers (240, 360 and 480 W, Figure 1a), CD at temperatures in the range of 50 to 70 °C (Figure 1b), and combined (CPD-VMD) drying consisting of CD at 60 °C and VMD at a magnetron power of 480 W (Figure 1c). The drying times, together with the maximum temperatures, the final moisture content and the constants of the Page model are listed in Table 1.
The Page model can be successfully used to describe the drying kinetics of the true lavender leaves dehydrated by the CD, VMD and CPD-VMD methods, characterized by high values of the determination coefficient (R2 > 0.99) and low RMSE values (<0.05). A good adaptation of the applied Page model for description of the drying kinetics can be found in many earlier publications of dill leaves, chanterelle and oyster mushrooms [23,24,25].
In the case of CD increasing the drying air temperature from 50 to 70 °C decreased the time of drying from 245 to 135 min, respectively. In VMD drying, radical reductions in the total drying time have been observed: the time was shortened from 32 to 14 min with a power change from 240 to 480 W. This radical reduction in the total drying time of VMD compared to CD is a result of the conventional water diffusion occurring, according to Fick’s law, that is supported by a pressure diffusion mechanism of the Darcy type [26]. Combined CPD and VMFD using 480 W, shortened the drying time of leaves almost 18-fold compared to CD at 50 °C. The use of CD and 480 W power caused a drop in the material temperature during VMD by 4 °C for leaves and 2 °C for flowers in reference to VMD 480 W. This condition is caused by the molecular distribution of water particles inside the dried CD and the distribution of water particles has an effect on the generation of heat energy production under microwave radiation during VMD [21,27,28]. Energy consumption during the CD of plant materials is much lower than in VMD [29,30]. In industrial conditions, the best solution is a combined drying process consisting of CPD and VMFD. The CD is very effective at the beginning of the drying process (the largest loss of water occurs during that phase) and VMD at the final stage of drying (removal of water strongly bound to the cellular structure of the material being dried) [18,27,28]. The final choice of recommended drying process should be related to the aspects of the dried material (volatile composition and sensory attributes) [27,31].

2.2. Volatile Constituents Profile of Fresh True Lavender Leaves

HS-SPME analysis coupled with the GC-MS technique had revealed one hundred and four peaks (one as a two compound mixture) recognized as volatile constituents, of which only one hundred of them could be identified (the mass spectra of unidentified constituents are available in supplementary materials). Volatile constituents of true lavender leaves are listed in Table 2. Among them nineteen compounds were qualified as monoterpene hydrocarbons, twenty-six as oxygenated monoterpenes, twenty-four as sesquiterpene hydrocarbons, nine as oxygenated sesquiterpenes, ten as esters and eleven as others.
The main headspace volatile constituents of the examined true lavender leaves samples were p-cymen-8-ol (4.09% ± 0.67), a mixture of borneol and lavandulol (4.66% ± 0.69), o-cymene (4.81% ± 0.52), bornyl acetate (5.57% ± 0.82), (E)-caryophyllene (6.11% ± 1.48), eucalyptol (7.28% ± 1.06) and γ-cadinene (10.53 ± 1.51). In less amounts cumin aldehyde (1.92% ± 0.59), τ-cadinol (2.04% ± 0.55), m-cymen-8-ol (2.09% ± 0.25), camphor (2.09% ± 0.92), p-cymene (2.58% ± 0.33), caryophyllene oxide (3.31% ± 0.18), limonene (3.42% ± 1.16) and 1-octen-3-pl acetate (3.80% ± 0.52), which have a significant influence on true lavender leaves’ fragrance quality, were identified. The most characteristic and valuable constituents for true lavender (flowers), linalool and linalyl acetate, represented 0.42% ± 0.03 and 2.21% ± 0.73 of the total amount of volatile constituents, respectively.
Similar findings were reported in recent studies where eucalyptol (8.50% and 31.9%), borneol (15.21% and 24%), camphor (2.00% and 16.1%), cumin aldehyde (0.50% and 2.2%) were identified as main volatile components of a true lavender leaves sample [33,34]. Also, one of these studies, by Hassanpouraghdam et al. [34] pointed out low amounts or even a lack of linalool (0.7%) and linalyl acetate. This result is contrary to the one obtained in this study, however it may be related to the slightly different plant chemotype or due to the fact that in Hassanpouraghdam’s study leaves essential oil was analyzed, not headspace volatiles. Nurzyńska-Wierdak and Zawiślak [35] have identified linalool and linalyl acetate in a similar ratio (1:5), and furthermore they also found higher amounts of γ-cadinene (3.4 ± 0.1) and caryophyllene oxide (7.2% ± 0.2).
Unfortunately, there is a lack of reports in literature including HS-SPME analysis of true lavender leaves volatile constituents. Most of available ones takes as study object lavender flowers or whole aerial parts of the plant, where linalool and linalyl acetate dominate in the chromatographic profile of the volatile constituents [36,37,38]. Torabbeigi and Aberoomand Azar [39] reported high amounts of eucalyptol (41.37%), camphor (15.83%), borneol (12.32%), α-pinene (4.66%), and γ-cadinene (1.07%) found by HS-SPME analysis of true lavender samples. At the same time they did not find any traces of linalool or linalyl acetate, suggesting that the major part of their samples were lavender leaves.

2.3. Effect of the Drying Methods on the Quantity of True Lavender Leaves Volatile Constituents

In the fresh true lavender leaves cultivated in Poland used in this study the content of essential oil was 3.082 g per 100 g−1 of DW. Overall this essential oil yield is high in comparison to previously reported ones, as Mirahmadi and Norouzi [40] obtained just 2.34% of essential oil from true lavender. Moreover, Milojević et al. [41] report the essential oil yield in sage and eucalyptus leaves ranges from 2% up to 2.87%. Changes of essential oil content, the concentration of sixteen major volatile constituents and linalool caused by the various drying methods are shown in Table 3.
In the case of essential oil content all applied drying methods significantly affected the raw material. The most efficient method was VMD 480 W (1.302 g per 100 g−1), followed by VMD 240 W (1.075 g 100 g−1), CD 70 °C (0.992 g per 100 g−1) and CPD-VMFD (0.921 g per 100 g−1) which were in overlapping significant groups. The percent recovery of essential oil in these methods were as follows 42.26%, 34.87%, 32.19% and 29.87%, in comparison to the amount of essential oil obtained from fresh sample. The less efficient drying method was CD 50°C, with a 19.06% recovery. The ratios of percent recovery between fresh sample and ones subjected to drying are presented in Figure 2. Baydar and Erbaş [42], Figiel et al. [19], Ghasemi et al. [43] found as well that due to the applied drying method or its parameters the decrease in essential oil yield of green plant parts may range as high as three to five times. Furthermore, Politowicz et al. [24] and Nöfer et al. [27], in the case of mushroom drying, observed similar effects to the ones found in this study.
The total essential oil content results are not equivalent to the content of sixteen major constituents. In fresh true lavender leaves, sixteen major constituents accounting for 66.51% of the total volatile constituents and changes caused by all drying methods were significantly distinct. Less differences were observed in the CD and CPD-VMFD methods (5.09–6.68 percentage points) and the highest were observed for the VMD method (22.54–24.04 percentage points). Further, some results in the case of particular constituents among the sixteen major ones are worth underlining. Again, all drying methods had a significant influence on a particular constituent share of total volatile constituents. The most interesting was the increase a share of linalyl acetate (even up to 11.06% of the share in the CD 60 °C method) along with the decrease of camphor share (down to 1.40%) at the same time. Also the share of linalool, the main aroma compound for true lavender, increased significantly after all drying treatments, except for VMD 240 W and VMD 360 W. These results suggest that applying drying, mainly CD, for true lavender leaves, may improve the characteristics for use in flavoring, in accordance with Kim and Lee [44] and Da Porto and Decorti [45], who report that the high ratio of linalool and linalyl acetate to camphor ratio is an important quality marker for lavender fragrance. Similar changes after applying drying were obtained by Śmigielski et al. [10]. Nevertheless, if the aim is to preserve as much essential oil as possible, the VMD methods would be more applicable. Very poor results, both in case of total essential oil and major volatile constituents, were obtained after the CPD-VMFD method, what is in contradiction with results obtained by Szumny et al. [20] for rosemary drying (R. officinalis), however the taxonomic differences between rosemary and true lavender should be considered.

3. Materials and Methods

3.1. Plant Material

The drying process was carried out on true lavender cultivated in Poland (Kawon-Hurt Nowak Sp.j. Company, Gostyń, Poland). The initial moisture content of material was 2.7 kg per kg of dry weight. The drying processes were stopped after no further change in weights was observed. Moisture content of samples was determined using a vacuum dryer (SPT-200. ZEAMIL Horyzont, Krakow, Poland).

3.2. Drying Methods

3.2.1. Convective Drying (CD)

CD was performed using the equipment designed and constructed at the Institute of Agricultural Engineering (Wrocław University of Environmental and Life Sciences, Wrocław, Poland). Samples were placed in the container (d = 100 mm) and dried at 50 °C. 60 °C and 70 °C—all with an air velocity of 0.5 ms−1.

3.2.2. Vacuum-Microwave Drying (VMD)

VMD was performed on samples with a SM 200 dryer (Plazmatronika, Wrocław, Poland). The dryer was equipped in cylindrical drum made of glass (18 cm of diameter × 27 cm of length). The drum with glass rotated with 6 rev·min−1. In the dryer system there was a BL 30P vacuum pump (Tepro, Koszalin, Poland), an MP 211 vacuum gauge (Elvac, Bobolice, Poland) and a compensation reservoir of 0.15 m3 capacity and a cylindrical tank. In this study, three power levels (240, 360 and 480 W) and pressures ranging from of 4 to 6 kPa were used. The maximum temperature of dried lavender leaves was measured right after the removal from the dryer using an i50 infrared camera (Flir Systems AB, Stockholm, Sweden).

3.2.3. Combined Drying—Pre-Drying by Convective Drying with Vacuum-Microwave Finishing-Drying (CPD-VMFD)

CPD-VMFD performed on samples consisted of CPD at a temperature of 60 °C until a moisture content of leaves was around 0.45 kg·kg−1 db, was reached, followed by VMFD at 480 W.

3.3. Modeling of Drying Kinetics

The drying kinetics of CD, VMD and CPD-VMFD were fitted based on the mass losses of the true lavender samples. For CD, weight losses were monitored every 2 min for the initial 20 min and then every 5 min thereafter until the end of the drying process.
VMD samples were monitored every 2, 3 and 4 min for 480, 360 and 240 W. Different drying time intervals were applied in order to ensure a similar energy input between subsequent measurements regardless of the microwave power level.
The moisture ratio (MR) of lavender leaves during drying experiments was calculated using the following equation:
M R = M ( t ) M e M o M e
where M(t) is the moisture content at time τ. Mo is the initial moisture content, and Me is the equilibrium moisture content (kg water/kg dry matter). The values of Me are relatively small comparing to those of M(t) or Mo. The error due to the simplification is negligible [46,47,48], thus the moisture ratio was calculated as follows:
M R = M ( t ) M 0
Table Curve 2D Windows v2.03 was used to fit the basic drying models to the measured MR determined accordingly to Equation (2). There are several drying models in the literature that can be used to describe the kinetics of drying plant materials. For drying model selection, drying curves were fitted to five well known thin drying models, including the modified Page model. Henderson–Pabis, logarithmic, Midilli-Kucuk, and Weibull ones. The best fit was determined using two parameters: the value of the coefficient of determination (R2) and root-mean squared error (RMSE). A model fits better if the value of R2 is closer to 1, and the RMSE value is closer to 0, using the following equations:
R 2 = i=1 N (M R pr e i MR ¯ exp ) i=1 N (M R exp i MR ¯ exp )
RMSE= 1 N i=1 N (M R exp i M R pr e i ) 2
where MR is moisture ratio, M R ¯ is the mean value of moisture ratio, “pre” and “exp” indicate predicted and experimental values, respectively, while “i“ indicates subsequent experimental data and N is the number of observations.
Tests conducted in this study proved that the best fitting was obtained for the modified Page model:
M R = A exp ( k τ n )
where A, n, and k are constants.

3.4. Solid-Phase Micro Extraction (SPME) Analysis

HS-SPME analysis (30 min exposure to a 2 cm DVB/CAR/PDMS fiber, Supelco, Bellefonte, PA, USA, followed by analyte desorption at 220 °C for 3 min) was performed on Varian CP-3800/Saturn 2000 apparatus (Varian, Walnut Creek, CA, USA) equipped with a Zebron ZB-5 MSI (30 m × 0.25 mm × 0.25 µm) column (Phenomenex, Shim-Pol, Poland). About 0.100 g of fresh or 0.150 g of dried sample was put in to headspace vials and kept in laboratory water bath at 70 °C. 0.5 mg of 2-undecanone (Sigma Aldrich, Saint Louis, MO, USA) as an internal standard was added.

3.5. GC-MS Analysis

The GC oven temperature was programmed from 50 °C, to 130 °C at rate 4.0°C. then to 180 °C at rate 10.0 °C, then to 280 °C at rate 20.0 °C. Scanning was performed from 35 to 550 m/z in electronic impact (EI) mode at 70 eV. Samples were injected at a 1:10 split ratio and helium gas was used as the carrier gas at a flow rate of 1.0 mL·min−1. Analyses were run in triplicate.

3.6. Hydrodistillation of Essential Oil (EO)

Hydrodistillation of EOs was carried out by applying a Deryng apparatus. About 200 g of fresh sample or 100 g of dried sample was placed in 2 L round bottom flask with 500 mL of added distilled water. Yield was assessed as a measured volume of essential oil.

3.7. Identification and Quantification of Volatile Compounds

Identification of all volatile constituents obtained by HS-SPME analysis and hydrodistillation were based on comparison of experimentally obtained compound mass spectra with mass spectra available in NIST14 database. Also the experimentally obtained retention indeces (RI) by Kovats were compared with RI available in the NIST WebBook and literature data [32]. The quantification analysis was performed using ACD/Spectrus Processor (Advanced Chemistry Development, Inc., Toronto, ON, Canada) through the integration of the peak area of the chromatograms.

3.8. Statistical Analysis

The data from drying kinetics were subjected to the analysis of variance using Tukey’s test (p < 0.05) and the data from quantitative essential oil and volatile constituents were subjected to the analysis of variance using Duncan’s test (p < 0.05), all using the STATISTICA 13.3 software for Windows (StatSoft, KrakowPoland).

4. Conclusions

One hundred constituents were identified in the volatile profile of true lavender leaves, with p-cymen-8-ol (4.09% ± 0.67), a mixture of borneol and lavndulol (4.66% ± 0.69), o-cymene (4.81% ± 0.52), bornyl acetate (5.57% ± 0.82), (E)-caryophyllene (6.11% ± 1.48), eucalyptol (7.28% ± 1.06) and γ-cadinene (10.53±1.51) as a major ones. When various methods are applied during the drying process, this profile is strongly affected. The optimal drying method is dependent on the purpose of the product utilization. A most interesting fact is that the drying process may decrease the share of camphor, while increasing the share of linalool and linalyl acetate which are the most desirable in components in true lavender aroma. This result may be a good starting point for considering the improvement of the value of true lavender leaves in comparison to its flowers for flavoring applications.

Supplementary Materials

The following files have been submitted as supplementary materials: mass spectra for unidentified compounds, mentioned in Table 2 Unknown compound mass spectra.pdf.

Author Contributions

Conceptualization, J.Ł. and A.S.; methodology, J.Ł., A.S., K.J. and M.S.; validation. J.Ł., A.S., K.J., M.S., K.M.; formal analysis. J.Ł., K.J. and M.S.; investigation. J.Ł., K.J. and M.S.; resources. A.S.; data curation. J.Ł.; writing—original draft preparation. J.Ł. and K.J.; writing—review and editing. J.Ł. and A.S., K.M.; visualization. J.Ł., K.J., M.S. and K.M.; supervision. A.S.; project administration. J.Ł.

Funding

This research was funded by the Faculty of Biotechnology and Food Science, Wrocław University of Environmental and Life Sciences, grant number B030/0003/1 and under the program of the Minister of Science and Higher Education “Strategy of Excellence University of Research” in 2018–2019 project number 0019/SDU/2018/18 in the amount of PLN 700 000.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Preedy, V.R. Essential Oils in Food Preservation, Flavor and Safety; Elsevier Inc.: London, UK, 2016; ISBN 9780124166417. [Google Scholar]
  2. Prusinowska, R.; Śmigielski, K.B. Composition, biological properties and therapeutic effects of lavender (Lavandula angustifolia L). A review. Herba Pol. 2014, 60, 56–66. [Google Scholar] [CrossRef]
  3. Lesage-Meessen, L.; Bou, M.; Sigoillot, J.C.; Faulds, C.B.; Lomascolo, A. Essential oils and distilled straws of lavender and lavandin: a review of current use and potential application in white biotechnology. Appl. Microbiol. Biotechnol. 2015, 99, 3375–3385. [Google Scholar] [CrossRef] [PubMed]
  4. Ayaz, M.; Sadiq, A.; Junaid, M.; Ullah, F.; Subhan, F.; Ahmed, J. Neuroprotective and anti-aging potentials of essential oils from aromatic and medicinal plants. Front. Aging Neurosci. 2017, 9, 1–16. [Google Scholar] [CrossRef] [PubMed]
  5. Ali, B.; Al-Wabel, N.A.; Shams, S.; Ahamad, A.; Khan, S.A.; Anwar, F. Essential oils used in aromatherapy: A systemic review. Asian Pac. J. Trop. Biomed. 2015, 5, 601–611. [Google Scholar] [CrossRef][Green Version]
  6. López, V.; Nielsen, B.; Solas, M.; Ramírez, M.J.; Jäger, A.K. Exploring pharmacological mechanisms of lavender (Lavandula angustifolia) essential oil on central nervous system targets. Front. Pharmacol. 2017, 8, 1–8. [Google Scholar] [CrossRef] [PubMed]
  7. Yu, S.H.; Seol, G.H. Lavandula angustifolia Mill. Oil and Its Active Constituent Linalyl Acetate Alleviate Pain and Urinary Residual Sense after Colorectal Cancer Surgery: A Randomised Controlled Trial. Evidence-based Complement. Altern. Med. 2017, 2017, 1–7. [Google Scholar] [CrossRef] [PubMed]
  8. Tomi, K.; Kitao, M.; Murakami, H.; Matsumura, Y.; Hayashi, T. Classification of lavender essential oils: sedative effects of Lavandula oils. J. Essent. Oil Res. 2018, 30, 56–68. [Google Scholar] [CrossRef]
  9. Uritu, C.M.; Mihai, C.T.; Stanciu, G.D.; Dodi, G.; Alexa-Stratulat, T.; Luca, A.; Leon-Constantin, M.M.; Stefanescu, R.; Bild, V.; Melnic, S.; et al. Medicinal plants of the family Lamiaceae in pain therapy: A review. Pain Res. Manag. 2018, 2018, 1–44. [Google Scholar] [CrossRef]
  10. Śmigielski, K.; Prusinowska, R.; Raj, A.; Sikora, M.; Woliñska, K.; Gruska, R. Effect of drying on the composition of essential oil from Lavandula angustifolia. J. Essent. Oil-Bearing Plants 2011, 14, 532–542. [Google Scholar] [CrossRef]
  11. Husnu Can Baser, K.; Buchbauer, G. Handbook of Essential Oils. Science, Technology and Applications; CRC Press: Boca Raton, FL, USA, 2009. [Google Scholar]
  12. Marín, I.; Sayas-Barberá, E.; Viuda-Martos, M.; Navarro, C.; Sendra, E. Chemical Composition, Antioxidant and Antimicrobial Activity of Essential Oils from Organic Fennel, Parsley, and Lavender from Spain. Foods 2016, 5, 18–27. [Google Scholar] [CrossRef]
  13. Hajhashemi, V.; Ghannadi, A.; Sharif, B. Anti-inflammatory and analgesic properties of the leaf extracts and essential oil of Lavandula angustifolia Mill. J. Ethnopharmacol. 2003, 89, 67–71. [Google Scholar] [CrossRef]
  14. Kirimer, N.; Mokhtarzadeh, S.; Demirci, B.; Goger, F.; Khawar, K.M.; Demirci, F. Phytochemical profiling of volatile components of Lavandula angustifolia Miller propagated under in vitro conditions. Ind. Crops Prod. 2017, 96, 120–125. [Google Scholar] [CrossRef]
  15. Mendoza-Poudereux, I.; Kutzner, E.; Huber, C.; Segura, J.; Arrillaga, I.; Eisenreich, W. Dynamics of monoterpene formation in spike lavender plants. Metabolites 2017, 7, 65. [Google Scholar] [CrossRef] [PubMed]
  16. Rocha, R.P.; Melo, E.C.; Radünz, L.L. Influence of drying process on the quality of medicinal plants: A review. J. Med. Plants Res. 2011, 5, 7076–7084. [Google Scholar] [CrossRef]
  17. Prusinowska, R.; Śmigielski, K. Losses of essential oils and antioxidants during the drying of herbs and spices. A review. Eng. Sci. Technol. 2015, 2, 51–62. [Google Scholar] [CrossRef]
  18. Figiel, A.; Michalska, A. Overall Quality of Fruits and Vegetables Products Affected by the Drying Processes with the Assistance of Vacuum-Microwaves. Int. J. Mol. Sci. 2017, 18, 71. [Google Scholar] [CrossRef] [PubMed]
  19. Figiel, A.; Szumny, A.; Gutiérrez-Ortíz, A.; Carbonell-Barrachina, Á.A. Composition of oregano essential oil (Origanum vulgare) as affected by drying method. J. Food Eng. 2010, 98, 240–247. [Google Scholar] [CrossRef]
  20. Szumny, A.; Figiel, A.; Carbonell-barrachina, A.A. Composition of rosemary essential oil (Rosmarinus officinalis) as affected by drying method. J. Food Eng. 2010, 97, 253–260. [Google Scholar] [CrossRef]
  21. Calín-Sánchez, Á.; Szumny, A.; Figiel, A.; Jałoszyński, K.; Adamski, M.; Carbonell-barrachina, Á.A. Effects of vacuum level and microwave power on rosemary volatile composition during vacuum—microwave drying. J. Food Eng. 2011, 103, 219–227. [Google Scholar]
  22. Sellami, I.H.; Wannes, W.A.; Bettaieb, I.; Berrima, S.; Chahed, T.; Marzouk, B.; Limam, F. Qualitative and quantitative changes in the essential oil of Laurus nobilis L. leaves as affected by different drying methods. Food Chem. 2011, 126, 691–697. [Google Scholar] [CrossRef]
  23. Motevali, A.; Younji, S.; Chayjan, R.A.; Aghilinategh, N.; Banakar, A. Drying kinetics of dill leaves in a convective dryer. Int. Agrophysics 2013, 27, 39–47. [Google Scholar] [CrossRef][Green Version]
  24. Politowicz, J.; Lech, K.; Sánchez-Rodríguez, L.; Szumny, A.; Carbonell-Barrachina, Á.A. Volatile composition and sensory profile of Cantharellus cibarius Fr. as affected by drying method. J. Sci. Food Agric. 2017, 97, 5223–5232. [Google Scholar] [CrossRef] [PubMed]
  25. Tulek, Y. Drying kinetics of oyster mushroom (Pleurotus ostreatus) in a convective hot air dryer. J. Agric. Sci. Technol. 2011, 13, 655–664. [Google Scholar]
  26. Lech, K.; Figiel, A.; Wojdyło, A.; Korzeniowska, M.; Serowik, M.; Szarycz, M. Drying Kinetics and Bioactivity of Beetroot Slices Pretreated in Concentrated Chokeberry Juice and Dried with Vacuum Microwaves. Dry. Technol. 2015, 33, 1644–1653. [Google Scholar] [CrossRef]
  27. Nöfer, J.; Lech, K.; Figiel, A.; Szumny, A.; Carbonell-Barrachina, Á.A. The Influence of Drying Method on Volatile Composition and Sensory Profile of Boletus edulis. J. Food Qual. 2018, 2018, 1–11. [Google Scholar] [CrossRef]
  28. Figiel, A. Drying kinetics and quality of beetroots dehydrated by combination of convective and vacuum-microwave methods. J. Food Eng. 2010, 98, 461–470. [Google Scholar] [CrossRef]
  29. Calín-Sánchez, Á.; Figiel, A.; Wojdyło, A.; Szarycz, M.; Carbonell-Barrachina, Á.A. Drying of Garlic Slices Using Convective Pre-drying and Vacuum-Microwave Finishing Drying: Kinetics, Energy Consumption, and Quality Studies. Food Bioprocess Technol. 2014, 7, 398–408. [Google Scholar] [CrossRef]
  30. Calín-Sanchez, Á.; Figiel, A.; Szarycz, M.; Lech, K.; Nuncio-Jáuregui, N.; Carbonell-Barrachina, Á.A. Drying Kinetics and Energy Consumption in the Dehydration of Pomegranate (Punica granatum L.) Arils and Rind. Food Bioprocess Technol. 2014, 7, 2071–2083. [Google Scholar] [CrossRef]
  31. Wojdyło, A.; Figiel, A.; Lech, K.; Nowicka, P.; Oszmiański, J. Effect of Convective and Vacuum-Microwave Drying on the Bioactive Compounds, Color, and Antioxidant Capacity of Sour Cherries. Food Bioprocess Technol. 2014, 7, 829–841. [Google Scholar] [CrossRef]
  32. Adams, R.P. Identification of essential oils by ion trap mass spectroscopy; Academic Press: San Diego, CA, USA, 2012. [Google Scholar]
  33. Adaszyńska-Skwirzyńska, M.; Śmist, M.; Swarcewicz, M. Comparison of extraction methods for the determination of essential oil content and composition of lavender leaves. Available online: http://ena.lp.edu.ua:8080/handle/ntb/27086 (accessed on 21 January 2019).
  34. Hassanpouraghdam, M.B.; Hassani, A.; Vojodi, L.; Asl, B.H.; Rostami, A. Essential oil constituents of Lavandula ofcinalis Chaix. from Northwest Iran. Chemija 2011, 22, 167–171. [Google Scholar]
  35. Nurzyńska-Wierdak, R.; Zawiślak, G. Chemical composition and antioxidant activity of lavender (Lavandula angustifolia Mill.) aboveground parts. Acta Sci. Pol., Hortorum Cultus 2016, 15, 225–241. [Google Scholar]
  36. An, M.; Haig, T.; Hatfield, P. On-site field sampling and analysis of fragrance from living Lavender (Lavandula angustifolia L.) flowers by solid-phase microextraction coupled to gas chromatography and ion-trap mass spectrometry. J. Chromatogr. A 2001, 917, 245–250. [Google Scholar] [CrossRef]
  37. Afifi, F.U.; Abu-Dahab, R.; Beltrán, S.; Alcalde, B.B.; Abaza, I.F. GC-MS composition and antiproliferative activity of Lavandula angustifolia Mill. essential oils determined by hydro-distillation, SFE and SPME. Arab. J. Med. Aromat. Plants 2016, 2, 71–85. [Google Scholar]
  38. Fu, J.; Zhao, J.; Zhu, Y.; Tang, J. Rapid Analysis of the Essential Oil Components in Dried Lavender by Magnetic Microsphere-Assisted Microwave Distillation Coupled with HS-SPME Followed by GC-MS. Food Anal. Methods 2017, 10, 2373–2382. [Google Scholar] [CrossRef]
  39. Torabbeigi, M.; Aberoomand Azar, P. Analysis of essential oil compositions of Lavandula angustifolia by HS-SPME and MAHS-SPME followed by GC and GC-MS. Acta Chromatogr. 2013, 25, 571–579. [Google Scholar] [CrossRef]
  40. Mirahmadi, S.F.; Norouzi, R. Influence of Thin Layer Drying on the Essential Oil Content and Composition of Lavandula officinalis. J. Essent. Oil-Bearing Plants 2016, 19, 1537–1546. [Google Scholar] [CrossRef]
  41. Milojevic, S.; Radosavljevic, D.; Pavicevic, V.; Pejanovic, S.; Veljkovic, V. Modeling the kinetics of essential oil hydrodistillation from plant materials. Hem. Ind. 2013, 67, 843–859. [Google Scholar] [CrossRef][Green Version]
  42. Baydar, H.; Erbaş, S. Effects of harvest time and drying on essential oil properties in lavandin (Lavandula × intermedia Emeric ex Loisel.). Acta Hortic. 2009, 826, 377–382. [Google Scholar] [CrossRef]
  43. Ghasemi, A.; Salehi, S.; Craker, L. Effect of drying methods on qualitative and quantitative properties of essential oil from the aerial parts of coriander. J. Dermatol. Sci. 2017, 4, 35–40. [Google Scholar]
  44. Kim, N.S.; Lee, D.S. Comparison of different extraction methods for the analysis of fragrances from Lavandula species by gas chromatography-mass spectrometry. J. Chromatogr. A 2002, 982, 31–47. [Google Scholar] [CrossRef]
  45. Da Porto, C.; Decorti, D. Analysis of the volatile compounds of flowers and essential oils from Lavandula angustifolia cultivated in northeastern Italy by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry. Planta Med. 2008, 74, 182–187. [Google Scholar] [CrossRef] [PubMed]
  46. Aghbashlo, M.; kianmehr, M.H.; Samimi-Akhijahani, H. Influence of drying conditions on the effective moisture diffusivity, energy of activation and energy consumption during the thin-layer drying of berberis fruit (Berberidaceae). Energy Convers. Manag. 2008, 49, 2865–2871. [Google Scholar] [CrossRef]
  47. Alibas, I. Characteristics of chard leaves during microwave, convective, and combined microwave-convective drying. Dry. Technol. 2006, 24, 1425–1435. [Google Scholar] [CrossRef]
  48. Dadali, G.; Apar, D.K.; Özbek, B. Microwave drying kinetics of okra. Dry. Technol. 2007, 25, 917–924. [Google Scholar] [CrossRef]
Sample Availability: Samples of the compounds are not available from the authors.
Figure 1. (a) Drying kinetics of true lavender leaves samples processed using VMD at magnetron powers 240, 360 and 480 W; (b) Drying kinetics of true lavender leaves samples processed using CD at temperatures of 50, 60 and 70 °C; (c) Drying kinetics of true lavender leaves samples processed using VMFD at 480 W after CPD at temperature 60 °C.
Figure 1. (a) Drying kinetics of true lavender leaves samples processed using VMD at magnetron powers 240, 360 and 480 W; (b) Drying kinetics of true lavender leaves samples processed using CD at temperatures of 50, 60 and 70 °C; (c) Drying kinetics of true lavender leaves samples processed using VMFD at 480 W after CPD at temperature 60 °C.
Molecules 24 00764 g001aMolecules 24 00764 g001b
Figure 2. Percent recovery of essential oil of true lavender leaves after applying various drying methods.
Figure 2. Percent recovery of essential oil of true lavender leaves after applying various drying methods.
Molecules 24 00764 g002
Table 1. Final moisture content (Mfwb), maximum temperature of the sample T, convective drying time (τ), vacuum microwave drying time (τ1), and constants A, k and n of the modified Page model describing the drying kinetics.
Table 1. Final moisture content (Mfwb), maximum temperature of the sample T, convective drying time (τ), vacuum microwave drying time (τ1), and constants A, k and n of the modified Page model describing the drying kinetics.
Drying ConditionsAConstants KnR2RMSEττ1T (°C)Mfwb (%)
CD 50 °C1.0000.02010.9530.99840.0125245-507.18
CD 60 °C1.0000.01251.1730.99910.0104145-607.09
CD 70 °C1.0000.02021.1500.99830.0156135-707.42
VMD 240 W1.0000.07361.3280.99890.0127-32646.78
VMD 360 W1.0000.12051.3580.99910.0104-21656.90
VMD 480 W1.0000.23391.3000.99910.0111-14666.87
CPD 60°C + VMFD 480 W0.4490.28950.8930.99820.01556010647.02
Table 2. Volatile constituents of fresh true lavender leaves.
Table 2. Volatile constituents of fresh true lavender leaves.
CompoundRT (min)Retention Indeces (RI)Content [%] 4
RI_lit 1RI_lit 2RI_exp 3
1-Penten-3-ol2.407-684686Tr 5
(Z)-3-Hexenal3.755 7978108080.23 ± 0.14
(E)-2-Hexenal4.765 8468548570.33 ± 0.17
(Z)-3-Hexen-1-ol4.821 8508578591.75 ± 0.35
1-Hexanol5.087 8638688710.32 ± 0.09
(E,E)-2,4-Hexadienal6.113 9099119130.15 ± 0.09
5.5-Dimethyl-1-vinylbicyclo[2.1.1]hexane6.380 -921924tr
Tricyclene6.479 9219269280.17 ± 0.03
α-Thujene6.591 9249309320.12 ± 0.05
α-Pinene6.788 9329399400.30 ± 0.07
Camphene7.209 9469549550.92 ± 0.19
3,7,7-Trimethyl-1.3.5-cycloheptatriene7.840 -972976tr
Sabinene7.911 6969769780.11 ± 0.03
1-Octen-3-ol8.038 9749799820.72 ± 0.06
3-Octanone8.260 9799869880.22 ± 0.03
β-Myrcene8.415 9889919930.52 ± 0.22
Mesitylene8.512 994995996tr
n-Decane8.681 1000100010000.19 ± 0.04
α-Phellandrene8.850 1002100510070.49 ± 0.28
3-Carene9.031 1008101110131.60 ± 0.66
m-Cymene9.397 1020102410262.58 ± 0.33
p-Cymene9.482 1022103010284.81 ± 0.52
Limonene9.634 1024103010333.42 ± 1.16
Eucalyptol9.692 1026103110357.28 ± 1.06
β-cis-Ocimene9.902 1032103810420.16 ± 0.03
β-trans-Ocimene10.240 1044105010530.14 ± 0.04
γ-Terpinene10.605 1054105910630.11 ± 0.03
trans-Sabinene hydrate10.886 1065107010710.23 ± 0.05
cis-Linalool oxide11.041 1067107410760.13 ± 0.03
unknown11.167 --1079tr
m-Cymenene11.419 1082108510860.50 ± 0.04
p-Mentha-2.4(8)-diene11.519 1085108810890.34 ± 0.10
p-Cymenene11.602 1089109110910.30 ± 0.03
Camphenone11.840 1095109610970.26 ± 0.02
Linalool11.953 1095109611000.42 ± 0.03
1.3.8-p-Menthatriene12.206 1108111011080.10 ± 0.02
1-Octen-3-ol acetate12.360 1110111211143.80 ± 0.52
cis-p-Menth-2-en-1-ol12.556 1118112111200.18 ± 0.04
trans-p-Mentha-2.8-dien-1-ol12.724 1119112211250.64 ± 0.19
cis-p-Mentha-2.8-dien-1-ol13.173 1133113711390.26 ± 0.03
trans-p-Menth-2-en-1-ol13.327 1136114011440.49 ± 0.08
Camphor13.496 1141114611492.09 ± 0.29
Tetrahydrolavandulol13.960 1157116111620.48 ± 0.09
Borneol + Lavandulol14.240 1165116911704.66 ± 0.69
Melilotal14.450 117911821176tr
Terpinen-4-ol14.631 1174117711810.59 ± 0.07
m-Cymen-8-ol14.774 1176117911842.09 ± 0.25
p-Cymen-8-ol14.914 1179118211884.09 ± 0.67
α-Terpineol15.082 1186118911930.31 ± 0.06
Myrtenol15.278 1194119511980.20 ± 0.14
trans-Piperitol15.671 1207120812100.65 ± 0.07
cis-Carveol16.035 1215121712220.37 ± 0.07
(Z)-Ocimenone16.159 1226122912260.26 ± 0.07
exo-Fenchyl acetate16.356 1229123212320.49 ± 0.04
cis-Verbenol16.623 123712441240tr
Cumin aldehyde16.748 1238124112441.92 ± 0.59
Carvone16.874 1246124312471.08 ± 0.28
Geraniol17.055 1249125212530.33 ± 0.29
Linalyl acetate17.263 1254125712592.21 ± 0.73
Geranial17.529 1264126712670.10 ± 0.08
trans-Carvone oxide18.021 1273127612810.33 ± 0.07
Bornyl acetate18.301 1284128512885.57 ± 0.82
Lavandulyl acetate18.428 1288129012921.72 ± 0.25
Terpinen-4-ol acetate18.761 1299129913010.18 ± 0.02
unknown19.124 --13140.61 ± 0.09
Myrtenyl acetate19.435 1324132613260.16 ± 0.06
δ-Elemene19.749 133513371337tr
α-Terpinyl acetate20.036 1346134913470.26 ± 0.08
α-Cubebene20.179 134813511351tr
α-Longipinene20.351 1350135213570.18 ± 0.01
unknown20.465 --13610.31 ± 0.05
Silphiperfola-4.7(14)-diene20.578 135813621365tr
Neryl acetate20.748 1359136413710.26 ± 0.06
α-Copaene21.134 1374137613830.14 ± 0.02
Geranyl acetate21.248 1379138113870.49 ± 0.11
α-Bourbonene21.375 138713881391tr
unknown21.461 139413961394tr
β-Longipinene21.634 1400140013990.26 ± 0.06
Sesquithujene21.833 140514051409tr
α-Cedrene22.049 1410141114201.01 ± 0.25
(E)-Caryophyllene22.176 1417141914276.11 ± 1.48
α-Bergamotene22.506 1432143514430.87 ± 0.33
Cadina-3.5-diene22.745 -145814551.12 ± 0.40
(E)-β-Farnesene22.889 1454145714621.35 ± 0.38
cis-Muurola-4(15).5-diene23.084 1465146614721.44 ± 0.45
4-epi-α-Acoradiene23.155 1474147514750.19 ± 0.00
Germacrene D23.441 1484148114890.58 ± 0.17
β-Himachalene23.629 150015001498tr
unknown23.741 1502-1505tr
α-Bulnesene23.840 1509150915110.92 ± 0.16
γ-Cadinene24.023 15131513152310.53 ± 1.51
cis-Calamenene24.149 1528152915310.65 ± 0.07
10-epi-Cubebol24.290 1533153515400.11 ± 0.05
α-Cadinene24.402 1537153815470.12 ± 0.02
Cadala-1(10).3.8-triene24.473 -15551552tr
trans-Cadinene ether24.669 1557-15640.35 ± 0.09
unknown24.851 --15760.13 ± 0.05
Spathulenol24.950 1577157815820.25 ± 0.05
Caryophyllene oxide25.158 1582158315953.31 ± 0.18
1-epi-Cubenol25.552 1627162816280.56 ± 0.03
τ-Cadinol25.860 1635134016562.04 ± 0.55
unknown26.056 --16730.11 ± 0.03
14-Hydroxy-4.5-dihydrocaryophyllene26.4071706170617060.21 ± 0.11
unknown26.911 1760176117640.23 ± 0.02
1 Retention indices according to Adams [32]; 2 Retention indices according to NIST14 database; 3 Relative retention indices calculated against n-alkanes; 4 % calculated from TIC data; 5 tr. < 0.1%.
Table 3. Variability of major volatile constituents, linalool, and total essential oil of true lavender leaves caused by various drying methods.
Table 3. Variability of major volatile constituents, linalool, and total essential oil of true lavender leaves caused by various drying methods.
Compound Drying Method
FreshCD 50 °CCD 60 °CCD 70 °CCPD-VMFDVMD 240 WVMD 360 WVMD 480 W
Content [%] 1
p-Cymene2.58 a2.73 c2.72 c1.76 d2.01 d,e2.15 e2.27 e3.50 b
o-Cymene4.81 a6.26 c5.65 d3.05 f3.69 e4.62 g4.73 g8.08 b
Limonene3.42 a3.27 f3.47 f1.31 e3.08 c,f1.97 d,e2.41 c,d6.99 b
Eucalyptol7.28 a5.01 b,c3.71 d5.12 b3.98 c,d3.25 d3.74 d3.44 d
1-Octen-3-ol. acetate3.80 a2.70 d,e2.82 d,e4.23 c6.22 b2.10 e4.42 c3.68 c,d
Camphor2.09 a2.32 b1.40 d1.89 c0.40 f1.12 e0.34 f0.39 f
Borneol + Lavandulol4.66 a7.63 b5.75 d6.07 d1.37 e4.78 c1.46 e1.35 e
m-Cymen-8-ol2.09 a3.18 c2.48 d3.67 b0.02 e2.74 d0.08 e0.07 e
p-Cymen-8-ol4.09 a6.31 c6.05 c7.17 b1.10 d6.07 c1.04 d0.89 d
Cumin aldehyde1.92 a3.59 c3.74 c4.48 b0.59 d4.30 b0.66 d0.59 d
Linalyl acetate2.21 a3.46 d11.06 b4.23 d1.60 e5.29 c1.66 e1.75 e
Bornyl acetate5.57 a3.54 c2.36 e4.04 b0.07 f3.07 d0.07 f0.14 f
Caryophyllene <(E)->6.11 a2.11 d2.78 c3.51 f6.38 b4.85 e5.28 e3.98 f
γ-Cadinene10.53 a3.67 f4.43 ef4.74 e8.48 c,d7.80 d9.20 c5.88 b
Caryophyllene oxide3.31 a2.43 c1.63 b2.12 b,c2.24 b,c2.11 b,c2.47 c1.89 b,c
τ-Cadinol2.04 a1.62 d1.44 d2.78 c2.74 c3.37 b,c3.85 b1.74 d
Ʃ66.51 a59.83 b61.42 b60.17 b43.97 c59.59 b43.68 c42.47 c
Linalool0.38 a4.32 c6.33 b4.71 c0.76 a,d6.62 b0.73 a,d1.16 d
TOTAL essential oil [mL 100g−1 dw] 23.082 a0.588 e0.726 f0.992 c,d0.921 b,c1.075 d0.881 b1.302 g
1 Values followed by the same letter within a row are not significantly different (p > 0.05, Duncan’s test); 2 Values obtained from steam distillation in Deryng apparatus.
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