# Aroma Profile of Monovarietal _Pet-Nat_ Ciders: The Role of Croatian Traditional Apple Varieties
## 3 Results and Discussion
### Volatile Compounds in Sparkling Pet-Nat Ciders
[59] suggest revising VPs as markers of sensory defects, since despite the high contents of VAs found in ciders, none of them presented this defective character. Clear phenolic off- flavor was not perceived under 11.8 mg\(\cdot\)L\({}^{-1}\) of 4-EC. 4-Vinylbaaicol characterized by a spicy and smoky, clove-like odor was detected with OAV > 1 only in 'Bobovac' sparkling cider, and 4-ethylgaiaicol (spice, clove, smoke) was detected in 'Crvenka' above its threshold (Table 5). As the only representative of _sulforous compounds_, methionol was detected in concentration above its threshold in all _Pet-Nat_ ciders. Fermentation aroma derived from the sulfur amino acid methionine, which occurs in many fruits, beer, and malt whisky, and presents an important constituent in naturally flavored products. According to [PERSON] et al. [71], it is one of the key aroma compounds of apple wines. Principal component analysis (PCA) was used to analyze the main aromatic compounds with OAV > 1 in _Pet-Nat_ ciders produced from different apple varieties. It can be observed from Figure 2 that PC1 explains 62% and PC2 38% of the of total variability among varieties. _Pet-Nat_ ciders from different varieties were clearly separated along PC1 and PC2 on the scatter plot. The bi-plot shows that apple variety influenced the aromatic profile of the final sparkling wines. 'Bozicnica' _Pet-Nat_ cider (on the right side of the bi-plot) is specific for the higher level of the 13 compounds from different groups of primary and secondary aromas. The 'Crvenka' _Pet-Nat_ cider located on the left negative side of PC1 is characterized for 4-ethylguaiacol and total C13 norisoprenoids content. In contrast, 'Bobovac' _Pet-Nat_ cider, on the positive side of PC2 is associated with 1-hexanol and ethyl hexanoate, (6Z)-nonen-1-ol and 4-vinylguaiacol. The PCA results show that, based on compounds with highest odor active values, the apple variety under conditions of natural fermentation plays an important role in the cider sensory profile. Figure 2: Principle component analysis (PCA): Distribution of _Pét-Nat_ ciders from three apple varieties in two-dimensional coordinate system defined by the first two principal components (PC1 and PC2) according to aromatic compounds contents with OAV \(>1\). \begin{table}
\begin{tabular}{l|c|c|c|c} \hline \hline \multicolumn{5}{c}{**Odor Active Value (OAV)**} \\ \hline
**Aromatic Compound** & \multicolumn{1}{c}{**’Božícnica’**} & \multicolumn{1}{c}{**’Bobovac’**} & \multicolumn{1}{c}{**’Crvenka’**} & \multicolumn{1}{c}{**Odor Descriptors**} \\ \hline
1-Hexanol & 3.25 & 3.96 & 3.04 & Cuttered grass [44] \\
1-Decanol & 1.02 & 0.31 & 0.25 & Pear, waxy, violet [72] \\
1-Propanol & 6.19 & 4.43 & 5.38 & Ripe fruit, alcohol [73] \\ (6Z)-Nonen-1-ol & 7.31 & 7.70 & 7.44 & Melon, green [74] \\
1-Dodecanol & 5.64 & 1.96 & 2.22 & Waxy, coconut [75] \\ \hline Hexanoic acid & 13.98 & 13.72 & 12.64 & Goaty, cheesy, oily [44] \\ Octanoic acid & 2.69 & 5.84 & 5.93 & Goaty, oily [44] \\ Isovaleric acid & 4.08 & 4.08 & 3.40 & Sweaty, cheesy [44] \\ \hline Citronellol & 1.50 & 1.14 & 0.81 & Rose, citrus [44] \\ \hline Ethyl hexanoate & 87.95 & 96.85 & 74.01 & Fruity, green apple [44] \\ Ethyl butanoate & 6.24 & 2.69 & 4.56 & Apple, fruity [44] \\ Ethyl 9-decenoate & 2.26 & 2.10 & 2.11 & Fruity, fatty [76] \\ Isoamyl acetate & 15.35 & 7.06 & 5.45 & Banana [44] \\ \hline
4-Ethylguaiacol & & & 3.69 & Phenolic, smoke, clove [44] \\ Eugenol & 8.11 & 7.94 & 8.05 & Cinnamon, clove [44] \\
4-Vinylguaiacol & 0.63 & 2.18 & 0.45 & Clove, curry, smoke [44] \\
4-Ethyl-phenol & 7.16 & & 0.28 & Leather, horse stable [44] \\ \hline Methionol & 23.75 & 9.60 & 17.55 & Potato, cauliflower [44] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Volatile compounds and odor descriptors of _Pét-Nat_ ciders with OAV \(>1\).