# Natural Variation of Volatile Compounds in Virgin Olive Oil Analyzed by HS-SPME/GC-MS-FID
## 3 Results and Discussion
Figure 1: Content (ng/g oil) of the main groups of volatile compounds in the oils from the WOGC cultivar subset. Numbers correspond to the WOGC cultivars displayed in Table 1.  
The levels of the branched-chain (BC) compounds in the different accessions of the olive collection subset are also important for the aroma of the oils, despite their low concentrations in the oils (average 106 ng/g oil, range of 20-740 ng/g oil). The 2- and 3-methyl-butanal contents suggest that these BC aldehydes contribute decisively to the VOO aroma, since they have OAV values higher than one in all the cultivars. This aroma significance for VOO is especially notable because they are located in the 'ripe fruit' sector of the statistical sensory wheel [20]. However, 2-methyl-butan-1-ol, which is responsible for the fusty off-flavor of the oil [34], was found below its odor threshold in all the cultivars assessed (Table 2), so it should not contribute to the aroma of the oils. Finally, only 2% of the cultivars of the olive collection subset had an OAV above one for limonene (Table 2), which suggests that this terpene is not an important contributor to VOO. Factor analysis allowed the correlations within the different volatile compounds in the olive oils to be explained. Figure 2 displays the factor analysis, considering only those factors with eigenvalues higher than one and using the normalized Varimax method. Those factors explained 77.97% of the total variance. The first factor explained 20.95% of the variance, while the second factor explained 12.66%. As shown, most of the C6 compounds spread along Factor 2 (dark gray ellipse), while most of the C5 compounds distributed along Factor 1. Three different groupings may be distinguished for \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Volatile Compound** & **Code** & **Min** & **Max** & **Mean** & **\% cv OAV \textgreater{} 1** \\ \hline C6/LnA aldehydes & (E)-hex-3-enal & 6C-1 & 116 & 924 & 371 & 25 \\  & (Z)-hex-3-enal & 6C-2 & 91 & 4598 & 884 & 100 \\  & (Z)-hex-2-enal & 6C-3 & 121 & 1290 & 646 & 80 \\  & (E)-hex-2-enal & 6C-4 & 4705 & 65,029 & 27,190 & 100 \\ C6/LnA alcohols & (E)-hex-3-enol & 6C-5 & 0 & 836 & 35 & 0 \\  & (Z)-hex-3-enol & 6C-6 & 45 & 3577 & 581 & 11 \\  & (E)-hex-2-enol & 6C-7 & 43 & 3293 & 252 & 0 \\ C6/LA aldehyde & hexanal & 6C-8 & 227 & 4451 & 1037 & 89 \\ C6/LA alcohol & hexan-1-ol & 6C-9 & 13 & 1463 & 314 & 26 \\ C5/LnA carbonyls & pent-1-en-3-one & 5C-1 & 126 & 1615 & 644 & 100 \\  & (Z)-pent-2-enal & 5C-2 & 8 & 175 & 57 & 0 \\  & (E)-pent-2-enal & 5C-3 & 45 & 226 & 105 & 0 \\ C5/LnA alcohols & pent-1-en-3-ol & 5C-4 & 80 & 634 & 257 & 10 \\  & (Z)-pent-2-en-1-ol & 5C-5 & 15 & 190 & 54 & 0 \\  & (E)-pent-2-en-1-ol & 5C-6 & 187 & 1564 & 510 & 90 \\ Pentene dimers & pentene dimer-1 & 5C-7 & 77 & 1195 & 457 & 0 \\  & pentene dimer-2 & 5C-8 & 65 & 1036 & 360 & 0 \\  & pentene dimer-3 & 5C-9 & 346 & 4840 & 1812 & 0 \\  & pentene dimer-4 & 5C-10 & 240 & 6363 & 2011 & 0 \\  & pentene dimer-5 & 5C-11 & 0 & 4513 & 1282 & 0 \\  & pentene dimer-6 & 5C-12 & 121 & 3909 & 1260 & 0 \\  & pentene dimer-7 & 5C-13 & 0 & 2847 & 628 & 0 \\ C5/LA carbonyls & pentan-3-one & 5C-14 & 17 & 270 & 91 & 0 \\  & pentanal & 5C-15 & 12 & 233 & 48 & 0 \\ C5/LA alcohol & pentan-1-ol & 5C-16 & 0 & 26 & 5 & 0 \\ LOX esters & hexyl acetate & E-1 & 5 & 6632 & 639 & 16 \\  & (E)-hex-2-en-1-yl acetate & E-2 & 8 & 1620 & 66 & 3 \\  & (Z)-hex-3-en-1-yl acetate & E-3 & 0 & 8696 & 1139 & 52 \\ non-LOX esters & methyl acetate & E-4 & 6 & 42 & 19 & 0 \\  & ethyl acetate & E-5 & 5 & 354 & 24 & 0 \\  & methyl hexanoate & E-6 & 6 & 128 & 29 & 0 \\  & ethyl hexanoate & E-7 & 0 & 359 & 45 & 0 \\ BC aldehydes & 3-methyl-butanal & BC-1 & 6 & 351 & 43 & 100 \\  & 2-methyl-butanal & BC-2 & 5 & 342 & 27 & 100 \\ BC alcohol & 2-methyl-butan-1-ol & BC-3 & 6 & 159 & 36 & 0 \\ Terpene & limonene & T-1 & 0 & 743 & 59 & 2 \\ \hline \end{tabular}
\end{table}