# Construction of IsoVoc Database for the Authentication of Natural Flavours
## 3 Results and Discussion
### Database Creation  
The number of unique VOCs present in at least five samples was 39 (Table 1). Not all variables were present in all samples. Since the dataset included many missing values for individual variables and contained only \(\delta^{13}\)C values for authentic natural samples and not for the synthetic samples, we used the Mann-Whitney U test rather than principal component analysis, PCA. We also excluded butyl propionate, isobutyl acetate, estragole, acetone, (Z)-2-hexen-1-ol, acetate, and isopropyl butyrate from Table 1, since there are no data on \(\delta^{13}\)C values reported in the literature. However, the \(\delta^{13}\)C values for authentic compounds determined in our study are presented, since they could be of a general interest to other researchers and are as follows:: butyl propionate (n = 18; \(\delta^{13}\)C from \(-\)38.3 to \(-\)29.6%), isobutyl acetate (n = 8; \(\delta^{13}\)C from \(-\)34.6 to \(-\)27.7%), estragole (n = 34; \(\delta^{13}\)C from \(-\)44.1 to \(-\)36.5%) in apple, and acetone (n = 23; \(\delta^{13}\)C from \(-\)43.7 to \(-\)35.5%), (Z)-2-hexen-1-ol, acetate (n = 14; \(\delta^{13}\)C from \(-\)37.1 to \(-\)33.2%) and isopropyl butyrate (n = 9; \(\delta^{13}\)C from \(-\)52.9 to \(-\)45.1) in strawberry. Figure 3: Comparison of \(\delta^{13}\)C values of VOCs in different fruit samples. Only aroma compounds present in at least five samples are shown. +++ ==ERROR: No output for this page== \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & & & & & & & & \\ \hline max & \(-\)28.0 & & \(-\)31.4 & \(-\)30.2 & \(-\)27.1 & & \(-\)30.1 & \(-\)32.6 \(-\)32.4 \\ No. & 5 & 1 & 3 & 3 & 5 & & 2 \\ min & \(-\)37.0 & \(-\)31.0 & & \(-\)31.2 & \(-\)31.1 & \(-\)33.7 & & \(-\)37.5 \\ max & \(-\)34.2 & \(-\)31.0 & & \(-\)29.8 & \(-\)28.6 & \(-\)29.7 & & \\  & & & & & Sour cherry & & \\ No. & & & 4 & 3.0 & & 1.0 & \\ min & & & \(-\)32.8 & \(-\)27.8 & & \(-\)25.5 & \\ max & & & \(-\)29.1 & \(-\)25.5 & & & \\ min \(-\)28.0 & \(-\)31.5 \(-\)27.0 \(-\)28.8 & \(-\)34.8 & \(-\)32.5 \(-\)26.0 \(-\)31.3 \(-\)28.6 & \(-\)27.2 \(-\)27.1 \(-\)25.7 & \(-\)25.5 & \(-\)27.0 & \(-\)36.1 \\ max \(-\)28.0 & \(-\)27.7 \(-\)24.4 \(-\)28.8 & \(-\)34.8 & \(-\)32.5 \(-\)26.0 \(-\)28.6 \(-\)26.8 & \(-\)22.8 \(-\)27.1 \(-\)25.7 & \(-\)25.5 & \(-\)26.2 & \(-\)36.1 \\ min \(-\)43.8 & \(-\)39.4 \(-\)44.5 \(-\)42.5 \(-\)41.9 & \(-\)34.4 & \(-\)37.0 \(-\)34.1 \(-\)39.8 \(-\)41.4 & \(-\)27.9 \(-\)33.0 \(-\)26.3 \(-\)31.2 \(-\)38.9 \(-\)33.2 & \(-\)38.3 \(-\)32.9 & \(-\)36.8 & \(-\)33.7 \(-\)28.2 \\ max \(-\)36.8 & \(-\)27.3 \(-\)37.0 \(-\)36.9 \(-\)38.3 & \(-\)30.5 & \(-\)30.0 \(-\)29.7 \(-\)31.3 \(-\)33.6 & \(-\)27.9 \(-\)33.0 \(-\)28.5 \(-\)30.0 \(-\)34.9 \(-\)32.1 & \(-\)29.7 \(-\)30.3 & \(-\)28.0 & \(-\)29.3 \(-\)26.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._All authentic samples were combined in one range (shown in dark green in Figure 4). What is clear is the overlap between individual ranges in \(\delta^{13}\)C values. Most data are in good agreement with literature data. For example, [PERSON] et al. [28] reported \(\delta^{13}\)C values for trans-2-hexenal ranging from \(-39.1\) to \(-31.5\%\), 1-hexanol ranging from \(-42.5\) to \(-38.4\%\) and trans-2-hexenol ranging from \(-42.2\) to \(-36.8\%\) in apple aroma. However, for certain VOCs, the authentic range of \(\delta^{13}\)C values observed in the literature is slightly shifted (e.g., 1-octanol, (E)-2-hexen-1-ol, hexanoic acid, hexyl butyrate, isobutyl acetate and linalool) compared with this study. For example, isoamyl acetate \(\delta^{13}\)C values for bananas are higher, ranging from \(-29.6\) to \(-27.2\%\)[22] compared to our study. This difference likely results from the different preparation method used or technological production, or unique fruit characteristics.