# Analysis of the Aroma Chemical Composition of Commonly Planted Kiwifruit Cultivars in China
## 3 Results and Discussion
### HS-SPME-GC-MS Analysis
#### 3.1.3 Qualitative and Quantitative Analysis of Volatile Components in Kiwifruit Samples
Therefore, the content of esters in imported cultivars and introduced cultivars was less than that of new Chinese breeds, and most esters provide the fruit with a complex fruit aroma. This indicates that the aroma chemical compositions of new Chinese breeds are more complicated, which may be caused by multiple crosses between cultivars. Among the esters, there were a total of 11 unique volatiles. They were present in five kiwifruit cultivars, of which Qinmei had a maximum of four unique volatiles, followed by three in Xuxiang, two in Huayou, and one in Jinhong No. 1 and Oriental Red. Figure S1B is a heat map analysis of alcohols and aldehydes in kiwifruit samples. Seventeen alcohol compounds were identified, which contributed to 0.88-70.73% of the TVC, with an average value of 35.81%. Thirteen aldehydes contributed to 0.86-77.57% of the TVC, with an average value of 39.22%. In alcohols, the main volatiles were ethanol and (E)-2-hexen-1-ol. The main volatile in aldehydes was (E)-2-hexenal, and the secondary volatiles were ethyl aldehyde, hexanal, and decanal. Ethanol had the highest alcohol content (1395.23 \(\upmu\)g/L) in Puyu, but its taste was not obvious in kiwifruit samples because of its high threshold (100,000.00 \(\upmu\)g/kg) and its ease of escape [21]. The concentration of (E)-2-hexen-1-ol was 1.29-294.54 \(\upmu\)g/L, and the concentration was highest in Jinshi. Among aldehydes, (E)-2-hexenal had the highest aldehyde content (6227.87 \(\upmu\)g/L) in Sungold, and it was present in all kiwifruit cultivars. Therefore, (E)-2-hexen-1-ol and (E)-2-hexenal were the components among alcohols and aldehydes that had a greater effect on the aroma of kiwifruit, and these were regarded as core aroma components of kiwifruit. In addition, the highest aldehyde concentration and proportion were present in Sungold (8031.25 \(\upmu\)g/L, 77.57% of TVC). The main aroma of aldehydes is the taste of green grass and vegetables, which indicates that the grassy aroma of Sungold is more prominent. Figure S1C shows a heat map analysis of ketones, acids, and alkanes in kiwifruit samples. Sixteen ketone compounds were identified, which contributed to 0.00-5.63% of the TVC, with an average value of 2.82%. Four acids contributed to 0.00-0.89% of the TVC, for which the average value was 0.45%, and twenty alkanes contributed to 0.00-3.89% of the TVC, for which the average value was 1.95%. There were no primary volatiles in ketones, acids, or alkanes. Ketones were not detected in Hongshi No. 2. In Jinhong No. 1 and Sungold, alkanes were not detected. Acids were detected only in Hongshi No. 2, Hongyang, Jinhong 50, Guichang, Jingong No. 7, and Qinmei. Based on this, ketones, acids, and alkanes seem to contribute only marginally to kiwifruit aroma composition. Figure S1D shows a heat map analysis of alkenes in kiwifruit samples. Forty alkene compounds were identified, which contributed to 0.18-31.50% of the TVC, with an average value of 15.84%. Alkenes are the category that contains the most volatiles. Among alkenes, there were three primary volatiles, namely, styrene, D-limonene, and 3-isopropylidene-6-methyl-1-cyclohexene. Among them, 3-isopropylidene-6-methyl-1-cyclohexene showed the highest alkene content (724.50 \(\upmu\)g/L) in Huayou. The highest alkene content overall was found in Sungold (1276.89 \(\upmu\)g/L, 12.33% of TVC), followed by Huayou (1060.51 \(\upmu\)g/L, 25.75% of TVC). Most alkenes have a sour taste of lemons or oranges, which indicates that the aroma characteristics of Sungold are more acidic than those of new Chinese breeds. Figure S1E shows a heat map analysis of aromatic hydrocarbons and their homologs and other components in kiwifruit samples. Sixteen aromatic hydrocarbons and their homologs were identified, which contributed to 0.19-5.34% of the TVC, with an average value of 2.77%. There were two primary volatiles, namely, o-xylene and 3,5-bis(1,1-dimethylethyl)-phenol. The highest aromatic hydrocarbon and homolog contents were present in Jinshi (267.43 \(\mu\)g/L, 5.16% of TVC).