## 2 Results
### Volatile Compounds of Banana Fruit (Musa AAA Group, Brazilian) at Different Stages of Ripening  
As shown in Table 2, in Brazilian banana fruit, 62 compounds, including esters, alcohols, aldehydes, ketones, acids and other minor compounds, were identified at three stages of ripening using the SPME method. The predominant volatile compound was aldehyde at the stage of mature-green, which accounted for 69.31% of the total content, while compounds such as hexanal and _trans_-2-hexenal accounted for 35.92% and 31.17%, respectively. It has been reported that the C\({}_{5}\), C\({}_{6}\)-alcohol, aldehyde and ketone together form a grassy aroma [18]. These aldehydes have grass typical flavor smells, which represented the characteristic aroma substances of banana at this stage. In addition, the level of 1-hexanol was quite high, accounting for 21.47% of the total content. However, few esters were detected at this stage. At the color-turning stage, the levels of \({}^{\prime}\)green aroma\({}^{\prime}\) compounds decreased dramatically, and a large number of esters were generated. Acetate, butyrate and methyl-butyrate ester were the most abundant esters, accounting for more than 70% of the total esters produced. 1-butanol, 3-methyl-, acetate (14.34%), butanoic acid, 3-methylbutyl ester (18.7%), and butanoic acid, 3-methyl-, 3-methylbutyl ester (14.03%) were also present. These esters are the most important compounds at the ripening stage of banana fruit. Among them, the branched-chain ester accounted for 85.49% of the total esters. In addition, some hydrocarbons were detected at this stage, and the aldehyde composition did not change significantly. When fruit reached the full-ripening stage, total volatile production increased continuously and slowly. The contents of certain typical aroma compounds such as 1-butanol, 3-methyl-, acetate (from 14.34% to 11.55%), butanoic acid, 3-methyl-, 3-methylbutyl ester (from 14.03% to 13.71%) remained relatively stable at this stage, but butanoic acid, 3-methylbutyl ester decreased from 18.7% to 11.9%. The proportion of total aldehydes decreased rapidly. Meanwhile, the level of ethanol increased. The variety and relative contents of ketones increased gradually, but hydrocarbons were not detected at this stage. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Mativity**} & \multicolumn{2}{c}{**Glucose**} & \multicolumn{2}{c}{**Fructose**} & \multicolumn{2}{c}{**Sucrose**} \\ \cline{2-7}  & **Fenjiao** & **Brazilian** & **Fenjiao** & **Brazilian** & **Fenjiao** & **Brazilian** \\ \hline Green & 29.2 \(\pm\) 14.1 \({}^{\text{a}}\) & 0.5 \(\pm\) 0.1 \({}^{\text{b}}\) & 33.3 \(\pm\) 11.3 \({}^{\text{a}}\) & 0.2 \(\pm\) 0 \({}^{\text{b}}\) & 19.2 \(\pm\) 4.7 \({}^{\text{a}}\) & 1.1 \(\pm\) 0.3 \({}^{\text{b}}\) \\ Turning & 87.4 \(\pm\) 3.3 \({}^{\text{a}}\) & 33.4 \(\pm\) 7.3 \({}^{\text{b}}\) & 75.8 \(\pm\) 2.9 \({}^{\text{a}}\) & 25.5 \(\pm\) 5.6 \({}^{\text{b}}\) & 64.2 \(\pm\) 8.5 \({}^{\text{a}}\) & 61.3 \(\pm\) 20.5 \({}^{\text{a}}\) \\ Full-Ripening & 112.5 \(\pm\) 2.5 \({}^{\text{a}}\) & 74.5 \(\pm\) 4.1 \({}^{\text{b}}\) & 99.3 \(\pm\) 4.7 \({}^{\text{a}}\) & 57.1 \(\pm\) 3.5 \({}^{\text{b}}\) & 23.6 \(\pm\) 5.0 \({}^{\text{b}}\) & 75.9 \(\pm\) 16.7 \({}^{\text{a}}\) \\ \hline \end{tabular} Note: Statistical analysis was performed by [PERSON]’s multiple range test. Means with different letters (\({}^{\text{a}}\)) within a row are significantly different at \(p<0.05\).  
\end{table} 
Table 1: Changes in soluble saccharide content in banana fruit at various stages of ripening (mg\(\cdot\)g\({}^{-1}\)).