# Evaluation and Comparison of Pear Flower Aroma Characteristics of Seven Cultivars
## 4 Discussion  
In this study, ninety-three volatile compounds were identified from the flower of different pear cultivars. Of those ninety-three chemicals, esters, alcohols, aldehydes, alkanes, and terpenoids were the dominant volatiles but showed noticeable differences in their amounts among different cultivars. Overall, volatiles in all cultivars were not distributed uniformly. This phenomenon was consistent with the previous studies on citrus flowers [39], Watermelon Rind [40], _Polianthe tuberosa_ L. flower [41], and peach [42]. The aroma characteristics showed pear flower odor was complicated, involving a series of odor types. In this study, several aldehydes, alcohols, and terpenoids were commonly found in each cultivar and presented an intense citrus odor like orange or lemon,  
Figure 6: Hierarchical clustering heatmap of selected odorants in flowers of seven pear cultivars. Each colored cell on the map corresponds to OAVs of the odorants, with the samples in the rows and compounds in the columns. and floral fragrance like rose or hyacinth [42]. Moreover, a certain amount of fatty and waxy odorants with oil-like or balsam-like were found in Bayuesu and Xizilu flowers and several C6 aldehydes, alcohols, and related esters were detected in Anli flowers known as green leaf volatiles (GLVs) [11]. However, not all volatile compounds observed in pear flowers actually affect the aroma [17; 43]; alkanes, as the major components of plant wax, were ubiquitous in all pear cultivars, always had less contribution to aroma but more for the fragrance lasting [42]. Somewhat unexpectedly, \(\alpha\)-pinene, \(\gamma\)-terpinene, d-camphor, and geraniol generally exist in the flowers of plants but were hardly recognized in this experiment [44; 45]. OAV was the ratio of concentration to the sensory threshold for a particular volatile compound [42]. The specific intensity and tendency of active odorants, which could be obtained by combining OAV and odor descriptor [43], provided further information on their important role in flavor [46]. In this study, OAVs of related odorants were further calculated to evaluate the aroma attributes of pear flowers. The lower threshold values of phenethyl acetate, 1-octanal, 1-nonanal, methyl 2-hydroxy-3-methyl pentanoate, 1-decanal, phenyl acetaldehyde, 2-pentyl-furan, and eugenol, typically showed higher OAVs and can be considered as the primary contributors of pear flower, presenting strong citrus, floral, and waxy notes [32]. Furthermore, some other volatiles with high OAVs were also observed in special cultivars, such as hexyl acetate, (\(Z\))-3-hexenyl acetate correlated with the fruity and green odor detected in Anli flower; (\(E\))-2-nonenal, 1-decanol, linalool correlated with fatty and floral odor [47] in Bayuesu and Xizilu flower; phenyl acetaldehyde and eugenol correlated with hyacinth and clove flavor [23] in Golden and Brown peel flower; and (\(E\))-\(\beta\)-damascone correlated with floral and fruity notes [47; 48] was just observed in Lyubaoshi flower. To sum up, the pear flower samples were characterized mainly by fruity, aldehyde, green, floral, citrus, fatty, waxy, and pungent notes. As reported previously [45; 49; 50], the relationship between aroma components and people's perception have always been a difficult and inadequately settled problem. For pear flowers, there is a lack of reference for evaluating the aromatic series and indicators for understanding the aroma characters. Still, in this study, there were obvious differences observed based on the aroma profiles conducted to compare the aroma attributes of different pear flowers. The aroma profiles indicated the major aroma characteristic between Bayuesu and Xizilu flower were much similar, with higher aldehyde, waxy, and fatty odor; the profile of Brown peel flowers were close to Golden pear, showing a high abundance in the series of aldehyde and floral flavor; and Lyubaoshi flower showed a high abundance of aldehyde and fruity series.