## 3 Results and Discussion
### Analysis of Volatile Compounds in Three Wines with Different Levels of Infestation  
#### 3.2.1 Screening for Characteristic Flavor Substances  
Esters were the most abundant substances detected in the test samples. Ethyl acetate, ethyl caprate, isoamyl acetate, phenylethyl acetate, ethyl caprylate, ethyl laurate, and ethyl butyrate were detected in the samples from groups B and C (Table 5). These are considered the most important aromatic substances contributing to the fruity character of wines [20; 21]. The lower ester content in group B compared to group C is consistent with the results described by [PERSON] et al. [22], which showed elevated esterase activity in grapes infested with Botrytis cinerea, resulting in the decreased ester content of noble rot wines. It is noteworthy that the content of most ester compounds (such as ethyl caproate and ethyl caprate) in the three groups of wines is higher than that in conventional wines. This is specifically attributed to the infection of noble rot fungi, which increases the permeability of grape skins. Consequently, a large amount of precursor substances such as sugars and amino acids in the pulp accumulate, providing sufficient substrates for ester synthesis during the yeast fermentation stage and leading to the excessive production of esters [22]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Serial**} & \multirow{2}{*}{**Aromatic Substances**} & \multirow{2}{*}{
\begin{tabular}{c} **Threshold** \\ **(ug/L)** \\ \end{tabular} } & \multicolumn{2}{c}{**Mass Concentration (ug/L)**} & \multirow{2}{*}{**Odor Description**} \\ \cline{3-3} \cline{5-6}  & & & & & \\ \hline Esters & & & & & \\ A1 & Ethyl acetate & 7500 & 9934 \(\pm\) 1683 & 12,857 \(\pm\) 901 & 11,890 \(\pm\) 602 & Fruity, sweet, nail polish \\ A2 & Isobutyl acetate & \(\backslash\) & 4301 \(\pm\) 5.5 & nd & nd & Aroma of ripe fruits \\ A3 & Ethyl butyrate & 20 & 1053 \(\pm\) 17 & 970 \(\pm\) 17 & 341 \(\pm\) 1.66 & Strawberries, apples, bananas \\ A4 & Isoamyl acetate & 30 & 46,334 \(\pm\) 970 & 2260 \(\pm\) 273 & 12,537 \(\pm\) 155 & Intense banana flavor, fruity, sweet \\ A5 & Ethyl valerate & \(\backslash\) & 81 \(\pm\) 143 & 104 \(\pm\) 4.9 & nd & \\ A6 & Hexyl acetate & 5 & 14,505 \(\pm\) 653 & 4583 \(\pm\) 312 & 3208 \(\pm\) 28 & Fruity, pear, cherry \\ A7 & Ethyl hexanoate & 80 & 6188 \(\pm\) 150 & 8343 \(\pm\) 154 & 16,547 \(\pm\) 227 & \textbackslash{}\) \\ A8 & Ethyl caprate & 100 & 71,988 \(\pm\) 1647 & 90,942 \(\pm\) 953 & 35,825 \(\pm\) 1234 & Coconut fruity aroma \\ A9 & Ethyl 3-hexenoate & \(\backslash\) & 26 \(\pm\) 0.67 & 11 \(\pm\) 0.82 & 7.0 \(\pm\) 0.04 & \textbackslash{}\) \\ A10 & Ethyl heptanoate & 300 & 191 \(\pm\) 1.46 & 253 \(\pm\) 4.1 & 217 \(\pm\) 1.01 & Fresh and fruity \\ A11 & Ethyl 9-hexadecenoate & \(\backslash\) & 11 \(\pm\) 0.55 & 57 \(\pm\) 0.65 & 261 \(\pm\) 0.87 & \textbackslash{}\) \\ A12 & Heptyl acetate & 670 & 117 \(\pm\) 0.75 & nd & 330 \(\pm\) 1.69 & Cherry and pear flavors \\ A13 & Octyl acetate & \(\backslash\) & 137 \(\pm\) 9.4 & nd & 120 \(\pm\) 1.11 & \textbackslash{}\) \\ A14 & Methyl caprylate & 200 & 200 \(\pm\) 2.6 & 245 \(\pm\) 3.2 & 460 \(\pm\) 0.86 & Intense citrus flavor \\ A15 & Ethyl caprylate & 580 & 145,402 \(\pm\) 11,456 & 90,798 \(\pm\) 564 & 38,020 \(\pm\) 668 & Pineapple, pear, floral, fruity, brandy \\ A16 & Propyl caprylate & \(\backslash\) & 82 \(\pm\) 1.99 & 47 \(\pm\) 1.13 & 70 \(\pm\) 0.91 & \textbackslash{}\) \\ A17 & Isoamyl caproate & \(\backslash\) & 180.31 \(\pm\) 4.29 & 108 \(\pm\) 0.80 & 330 \(\pm\) 1.78 & Apples, pineapples \\ A18 & N-butyl caprylate & \(\backslash\) & 142 \(\pm\) 2.7 & nd & nd & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of volatile components of wines. Alcohols are major secondary metabolites during fermentation and provide wines with their characteristic aromas [23]. Higher alcohols were more abundant in group A than in group B or C wine samples (Table 5). Higher alcohols are mainly produced by the metabolism of glucose and corresponding amino acids in yeast.