## 2 Results and Discussion
### 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 [PERSON] and [PERSON] [40] obtained just 2.34% of essential oil from true lavender. Moreover, [PERSON] 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 \({}^{\circ}\)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\({}^{\circ}\)C, with a 19.06% recovery. The ratios of percent recovery between fresh sample and ones subjected to drying are presented in Figure 2. [PERSON] and [PERSON] [42], [PERSON] et al. [19], [PERSON] 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, [PERSON] et al. [24] and [PERSON] et al. [27], in the case of mushroom drying, observed similar effects to the ones found in this study. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Drying Method**} \\ \cline{2-10}
**Compound** & **Fresh** & **CD 50 °C** & **CD 60 °C** & **CD 70 °C** & **CFD-VMFD** & **VMD 240 W** & **VMD 360 W** & **VMD 480 W** \\ \hline \multicolumn{10}{c}{**Content [\%]1**} \\ \hline \(p\)-Cymene & 2.58 ** & 2.73 ** & 2.72  & 1.76  & 3.05  & 4.62  & 4.73  & 8.08  \\ Limonene & 3.42  & 3.27  & 3.47  & 1.31  & 3.08  \\ Eucalyptus & 7.28  & 5.01  & 3.71  & 5.12  & 3.98  \\ 1-Octen-30-i. acetate & 3.80  & 2.70  & 2.82  & 4.23  & 6.22  & 2.10  & 4.42  & 3.68  \\ Campthor & 2.09  & 2.32  & 1.40  & 1.89  & 0.40  & 1.12  & 0.34  & 0.39  \\ Bornoel + Lavandul & 4.66  & 5.75  & 6.07  & 4.78  & 1.46  & 1.35  \\ \(m\)-Cymene-8-ol & 4.09  & 6.31  & 6.05  & 7.12  & 1.10  & 1.10  & 6.07  & 4.78  & 1.46  & 1.35  \\ Limonene & 3.42  & 3.46  & 1.11  & 3.08  & 4.23  & 1.11  & 3.08  & 1.11  & 1.12  & 6.09  \\ Eucalyptus & 7.28  & 5.01  & 3.71  & 5.12  & 3.98  \\ 1-Octen-30-i. acetate & 3.80  & 2.70  & 2.82  & 4.23  & 6.22  & 2.10  & 4.42  & 3.68  \\ Campthor & 2.09  & 3.18  & 4.87  & 4.86  & 4.87 [FOOTNOTE:3]Footnote 3: Values obtained from steam distillation in Drying apparatus. 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 \({}^{\circ}\)C method) along with the decrease of camphor share (down to 1.40%) at the same time.