# Evaluation and Comparison of Pear Flower Aroma Characteristics of Seven Cultivars
## 3 Results
### Multivariate Analysis  
In this study, PCA was carried out using OAVs and samples as the variables, to obtain an overview of relationships among different cultivars in terms of their active odorants. As can be seen from Figure 5, the first principal component (PC1) and second principal component (PC2) were extracted, it was noted that the linear combination of PC1 and PC2 explained 62.1% of the total variance of pear flower samples, indicated that these two factors were considered sufficient for further discussion. The information on relationships between the active odorants and the PCs was provided according to the location of plotted data. As shown, the seven cultivars can be classified into four clusters: cultivars Golden and Brown peel flowers were group together in the first quadrant, the relevant odorants were naphthalene, \(\beta\)-ocimene, phenethyl acetate, \(\alpha\)-farnesene, eugenol, 2-methyl naphthalene, and phenyl acetaldehyde; the second group contained Bayuesu and Xizilu flowers located in the left of the third quadrant, with high amounts of the chemicals 1-decanol, 1-heptanol, 1-undecanal, 1-octanal, 1-decanal, 1-decanal, 1-nonanal, hexyl 2-methylbutyrate, (_E_)-citral, 1-octanol, 1-nonanol, (_E_)-2-nonenal, and linaloolhe as the relevant odorants, which meant that these cultivars were positive related with the aldehyde, waxy, and fatty series; KorlaXiangli and Lyubaoshi flower were clustered as the third group distributed mostly near the origin, revealed that the flowers were slightly in floral, pungent and green series; cultivars Anli flower situated individual in the lower right corner of the fourth quadrant clustered as the forth group, related to the typical chemicals of methyl 2-hydroxy-3-methyl pentanoate, (_E_)-geranyl acetone, 1-hexanol, 6-methyl-5-hepten-2-one, (_Z_)-3-hexenyl acetate, acetophenone, 2-phenylethylanol, benzaldehyde, 2-pentyl-furan, and 2-phenylethyl formate, indicated this cultivar was rich in floral, fruity, and green odor.  
Figure 4: Radar map of aroma series based on the accumulated OAVs. **(a)** Anli, **(b)** Bayuesu, **(c)** Brown peel, **(d)** Golden, **(e)** KorlaXiangli, **(f)** Lyubaoshi, and **(g)** Xizilu.  
Figure 5: PCA scores plots result using seven pear flower samples as score values and OAVs of selected odorants as loading values. The odorant names correspond to the codes of compounds listed in Table 3.  
Application of HCA can interpret the results in an intuitive graphical way; cultivars in the same cluster displayed similar characters, whereas the samples in different clusters were relatively different. In this study, the OAV data were also subjected to HCA and used to explore the heterogeneity between cultivars (Figure 6). Results showed the aroma profiles of different pear flowers were appropriately divided into two main branches, then were again subdivided into three groups. According to the dendrogram and heatmap obtained, Bayuesu had the highest odor-active compound similarity to the Xizilu flower and these were grouped in one cluster, with Golden and Brown peel flowers grouped in a second cluster, and Lyubaoshi and KorlaXiangli flowers grouped in the third cluster. The observed clusters can be explained by the similar odor type of the identified odorants. HCA also showed the highest diversity among the Bayuesu and KorlaXiangli flowers due to the significant differences in the kinds and amounts of the identified volatiles. Futhermore, the results suggested that the aroma of Anli flower was distinct from the other six cultivars. These results were consistent with the PCA analysis, indicating HCA was a powerful tool to validate the rationality of the clustering and reveal the characteristics of each group [38].