# Compositional Analysis and Aroma Evaluation of Feijoa Essential Oils from New Zealand
## 2 Results and Discussion
### Compositional Analysis of Feijoa Essential Oil from Four Cultivars  
The essential oils extracted from the four feijoa cultivars were subjected to compositional analysis by GC-MS. The identified compounds, with their identities and relative concentrations in the four essential oils, are summarized in Table 1. A total of 158 compounds were detected in the essential oils, by GC-MS. Among them, 89 compounds were reported in feijoa essential oil for the first time. More specifically, 114 compounds were detected in the essential oils from all four cultivars and a total of 137, 129, 148, and 141 compounds were found in the essential oils extracted from the Apollo, Unique, Opal Star, and Wiki Tu cultivar, respectively. As shown in Figure 3, the identified compounds (except the unknown compounds and flavone) can be classified into 10 groups. They are esters (40 compounds), sesquiterpenes (26), alcohols (19), aromatic hydrocarbons (17), ketones (11), monoterenes (9), hydrocarbons (7), aldehydes (6), ethers (2), and an acid (1). Apollo and Opal Star essential oils comprised of more ester compounds, 37 and 36 compounds, respectively, than the Unique (27 compounds) and Wiki Tu (29 compounds) essential oils. All four essential oils contained all of the detected sesquiterpenes, but the Wiki Tu essential oil had one less monoterene than the essential oils from the other three cultivars. The detected aromatic hydrocarbons varied significantly, reporting 5, 6, 16, and 17 compounds in the essential oils from the Apollo, Unique, Opal Star, and Wiki Tu cultivars, respectively. In addition, slight differences were seen in the composition of alcohol, ketone, aldehyde, hydrocarbon, ether, and acid compounds in the four essential oils. The concentration of each compound differed amongst the essential oils from the four selected cultivars. For example, the concentration of 3-octanone in the Opal Star essential oil was over  
Figure 3: Compound distribution in essential oils from four feijoa cultivars. Figure 2: Extraction yield of feijoa essential oil from four cultivars. Letters a, b, c are indicators for statistical significance (\(p<0.05\)), identical letters indicate no statistically significant difference. 30 times higher than that found in the Unique essential oil, and similarly with linalool, ethyl benzoate, (Z)-3-hexenyl butanoate, and (Z)-3-hexenyl hexanoate. The observed compositional variation among the four essential oils indicated the differences in the peel samples and could be useful to distinguish feijoa cultivars. Similar results were obtained by [PERSON] et al. [29], studying orange essential oil. Esters (40), terpen (35), and alcohols (19) are the top three dominant chemical groups in feijoa essential oil composition. The most abundant compounds (Table 1 and Figure 4) in feijoa essential oil were \(\beta\)-caryophyllene (No. 78, 95.64-176.74 mg/mL), humulene (No. 83, 41.12-112.77 mg/mL), germacrene D (No. 86, 58.98-128.46 mg/mL), ledene (No. 89, 104.09-191.99 mg/mL), \(\alpha\)-cadinol (No. 111, 62.22-105.78 mg/mL), \(\beta\)-elemene (No. 75, 49.19-89.72 mg/mL), and \(\delta\)-cadinene (No. 91, 48.12-69.23 mg/mL). This is generally consistent with a previous report [28]. It is interesting to note that all these compounds, except \(\alpha\)-cadinol (alcohol), were terpen, indicating that terpen, which are frequently found to be major components in plant essential oils in general [29; 30], were dominant compounds in feijoa essential oils. Esters were also major components (40 compounds in total) in feijoa essential oils, although the average concentration of the ester compounds was much lower than that of the terpen (Figure 4). Important esters, of which the concentrations were above 1 mg/mL (Table 1 and  
Figure 4: Heat map of dominant compounds in feijoa essential oils from four cultivars. (**I**)—for ester compounds; (**II**)—for terpen compounds; (**III**)—for alcohol compounds. Feijoa cultivars, A—Apollo, U—Unique, OS—Opal Star, WT—Wiki Tu.