## 3 Results and Discussion
### Stepwise LDA Based on Volatile Compounds Analysis
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Wavenumber (cm\({}^{-1}\))** & **Functional Group** & **Peak Performance** & **Assignment** & **Reference** \\ \hline \(\sim\)3270 & O–H & Sugars–Water & Stretching & [34] \\ \(\sim\)2927 & C–H and C–N & Carboxyl acids and Amino acids & Stretching & [34] \\ \(\sim\)1643 & O–H & Water & Deformation & [34] \\ \(\sim\)1414 & C–O–H, –CH\({}_{2}\) and C–H & Glucose and Alkene & Stretching & [34, 35, 36] \\ \(\sim\)1341 & O–H (C–OH) & Fructose & Bending & [36] \\ \(\sim\)1253 & C–C and –CH\({}_{2}\)– & Glucose and fructose & Stretching and Bending & [34, 35, 36] \\ \(\sim\)1146 & C–O, C–O–C & Sugars & Bending, Stretching & [36] \\ \(\sim\)1044 & C–O (C–OH), C–O & Sugars and fructose & Stretching & [34, 35, 36, 37] \\ \(\sim\)1025 & C–O & Glucose & Stretching & [36] \\ \(\sim\)918 & C–H & Sugars, Glucose & Bending & [36] \\ \(\sim\)865 & C–C & Fructose & Stretching & [36] \\ \(\sim\)818 & C–C–H & Fructose & Stretching & [36] \\ \(\sim\)777 & C–C–H & Fructose & Deformation & [36] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The main peaks and their assignments of the honey samples attenuated total reflection (ATR)-FTIR spectra. The standardized canonical discriminant function coefficients revealed that two aldehydes were the key volatiles, which can be defined as reliable for the discrimination of the honey groups. In more detail, based on the first discriminant function, the volatile compound 2-(4-methylcyclohex-3-en-1-yl)proponal permitted enhanced discrimination of citrus honey from the other honey groups, while according to the second function, 2-phenylacetaldehyde allowed better discrimination of thyme honey from citrus, pine, and fir honey. The aldehyde, 2-(4-methylcyclohex-3-en-1-yl)proponal is produced by (E)-8-hydroxylinalool and via the allylic rearranged 8-hydroxygeraniol [44]. Moreover, it has been previously observed in the volatile fraction of monofoloral Greek [13; 24; 28] and Spanish citrus honey [45]. The aromatic 2-phenylacetaldehyde has also been previously reported as a \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Classification Results 1,2**} \\ \hline \multirow{6}{*}{Original} & \multirow{2}{*}{**Label**} & \multicolumn{4}{c}{**Predicted Group Membership**} & \multirow{2}{*}{**Total**} \\ \cline{3-4} \cline{6-7}  & & & **Fir Honey** & & **Thyme Honey** & **Pine Honey** & **Citrus Honey** & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \hline \multirow{6}{*}{Crowal} & \multirow{2}{*}{Count} & Fir honey & 11 & 0 & 3 & 0 & 14 \\  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \hline \multirow{6}{*}{Cross-validated 3} & \multirow{6}{*}{Count} & Fir honey & 78.6 & 0.0 & 21.4 & 0.0 & 100.0 \\  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \cline{3-4}  & & & & & & & \\ \hline \hline \end{tabular} \({}^{1}\) 85.5% of original grouped cases correctly classified; 2 82.3% of cross-validated grouped cases correctly classified; 3 cross validation is done only for those cases in the analysis. In cross validation, each case is classified by the functions derived from all cases other than that case.  
\end{table} 
Table 2: Classification results are based on volatile compounds analysis. Figure 6: Discrimination results based on volatile compound analysis. characteristic volatile compound identified in the majority of thyme honey samples from Greece [13; 46], Italy [47], and Spain [45]. Furthermore, octane, nonanol, and nonanoic acid have been reported as dominant volatile compounds in pine [4; 20] and fir [27] honey. Finally, methyl 2-hydroxybenzoate was identified in the majority of the fir honey samples studied; however, according to literature, it has not been previously identified in fir honey. [PERSON] et al.