## 3 Results and Discussion
### Aroma Composition  
GC-MS chromatograms of the samples with respect to their treatment are shown in Figure 7. In this study, the number of volatile components detected varied from 42 to 92, depending on the treatment. There were three particularly large peaks (P1, P2, and P3) in Figure 7: P1 was presumed to represent Linalool, a monoterpene present in the aroma components of various fruits, vegetables, spices, coffee, and tea. It is used in cosmetics as a floral perfume, and in confections and soft drinks, because of its lily-like aroma. P2 was presumed to represent _trans_-alpha-bergamotene, which is an aromatic component of Bergamotene with a partially different bonding and atom arrangement. P3 was assumed to be 2-methoxy-3-(2-propenyl)-phenol, a type of phenolic. All three components have been previously reported in basil [35; 36]. Figure 8 depicts the change in peak areas (PA) of Linalool, _trans_-alpha-bergamotene, and 2-methoxy-3-(2-propenyl)-phenol with each treatment. During S treatment, the PA of Linalool and 2-methoxy-3-(2-propenyl)-phenol decreased with increasing steam-heating time compared with that during NS, with a remarkable decrease observed > 2 min (Figure 8A,C). The PA of _trans_-alpha-bergamotene was not affected by S treatment, and its duration and showed a remarkable decrease only at S10 (Figure 8B). In some herbs, such as basil, destruction of the glandular trichome and reduction of aromatic compounds have been reported with steam-heat treatment. In this study, SEM images also confirmed the destruction of the glandular trichome at S2 and above (Figure 1A). The glandular trichome is filled with aromatic compounds unique to each plant species. Linalool and 2-methoxy-3-(2-propenyl)-phenol were assumed to have undergone oxidation and hydrolysis reactions [37] and evaporation [38] after the destruction of the glandular trichome, resulting in a decreased PA. On the contrary, _trans_-alpha-bergamotene, which was less affected by S treatment, did not show a decrease in PA even at S5, indicating that it is less prone to chemical reaction and evaporation after-glandular trichome destruction compared with other components. The highest PA values for drying methods and temperature were different during SD for Linalool, MD 60 \({}^{\circ}\)C for _trans_-alpha-bergamotene, and FD for 2-methoxy-3-(2-propenyl)-phenol. However, a common trend was observed for all three components, with a marked decrease in PA above MD 80 \({}^{\circ}\)C and approximately the same value from 80 \({}^{\circ}\)C to 100 \({}^{\circ}\)C (Figure 8a-c). SEM images showed the destruction of the glandular trichome at S2. However, it remained unchanged, albeit in a deformed state, during MD, even at 100 \({}^{\circ}\)C. Since the S treatment involved FD, the heating time was the same as the S treatment time. Therefore, the maximum heating time for S treatment is 10 min. On the contrary, the heating times for MD 80 \({}^{\circ}\)C, 90 \({}^{\circ}\)C, and 100 \({}^{\circ}\)C were 45, 26, and 22 min, respectively, which were longer than those for the S treatment. Therefore, the volatile components of the glandular trichome could have decreased due to the high temperature and prolonged heating time, even without disruption. _Trans_-alpha-bergamotene was less affected by the S treatment than the other two components; however, PA was greatly reduced at S10 (Figure 8B). Therefore, _trans_-alpha-bergamotene is less prone to chemical reactions than Linalool, 2-methoxy-3-(2-propenyl)-phenol but volatilizes or decomposes under high temperature and prolonged heating. Linalool maintained levels similar to those seen during FD of up to MD 70 \({}^{\circ}\)C in the absence of glandular trichome disruption. 2-methoxy-3-(2-propenyl)-phenol was the most sensitive to heat among the three components since it decreased at SD and MD 40 \({}^{\circ}\)C even without glandular trichome disruption.