## 3 Results and Discussion
### Planning and Selection of Volatile Markers Suitable for Formulations
In the case of winey-vinegary defect, the individual dilutions (1000 mg/kg) of compounds determined that the aroma provided by acetic acid, ethyl acetate, and ethanol were highly related with the aroma of the sensory defect when this dilution was evaluated by panelists with a scale of three degrees (low-medium-high representativeness). Consequently, they were selected to begin the formulations and were nominated as \"primary compounds\" whose aroma could be modified by the addition of others. In particular, acetic acid and ethyl acetate were related with the winey aroma, while ethanol was more related to fermentative and winey notes. The compound 3-methyl-1-butanol was excluded since its aroma was considered far from the target aroma. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensory Defect** & **Volatile Marker** & **Sensory Characteristics** & **Odor Threshold (mg/kg)** \\ \hline \multirow{4}{*}{Winey-vinegary} & Acetic acid & Vinegary, sour & 0.50 \\  & Ethyl acetate & Sticky & 0.94 \\  & Ethanol & Alcohol & 30.00 \\  & 3-Methyl-1-butanol & Whiskey & 0.10 \\ \hline \multirow{4}{*}{Rancid} & Pentanal & Oily & 0.24 \\  & Hexanal & Oily, fatty & 0.08 \\  & Heptanal & Oily, fatty & 0.50 \\ \cline{1-1}  & \(E\)-2-Heptrenal & Tallowy, oxidized & 0.04 \\ \cline{1-1}  & Octanal & Fatty & 0.32 \\ \cline{1-1}  & Nonanal & Waxy, fatty & 0.15 \\ \cline{1-1}  & \(E\)-2-Decenal & Fishy, fatty & 0.01 \\ \cline{1-1}  & Hexanoic acid & Rancid & 0.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Volatile markers of VOO sensory defects winey-vinegary and rancid, sensory characteristics and corresponding odor threshold relating to an oil matrix. Figure 1: Scheme to select volatile compounds as candidates to formulate RMs of aroma sensory defects detected in VOOs. Note: 1 in this work sensory detect refers to rancid or winey-vinegary; 2 volatiles can result from oxidation (rancid defect) or fermentation (winey-vinegary defect) processes; 3 the concentration of these compounds may exceed or not their odor threshold, and can or cannot smell like the sensory defect. Figure 2: Flow diagram for formulating RMs. Note: \({}^{1}\) reformulation includes selection/removal of compounds and/or new adjustment of concentrations; \({}^{2}\) the question refers to perception of a “chemical” aroma that is far from the natural off-flavors found in VOO. In the case of rancid defect, all the compounds were characterized by a high representativeness and all provided similar aromas (oily, fatty), except for _E_-2-decenal (fishy, fatty) and hexanoic acid (rancid). Hexanal and nonanal were selected as \"primary compounds\" to prepare the first formulations because of their demonstrated relationship with lipid oxidation and the rancidity process of fatty foods [34; 35], including VOO [36; 37; 38; 18]. The aforementioned volatiles were considered as primary compounds and were identified in 63 VOOs that covered the three categories (EV, V, L) and all possible qualities. Table 2 shows the relative areas of these compounds. The study was based on relative areas instead of quantification by calibration curves, since the range of possible concentration values reached high values (in some cases with median of the defect around 8) and therefore competition phenomena may alter the accuracy of the quantification. The objective was to establish the high range of relative areas that needs to be reproduced in a formulated RM using the same volatile compounds at similar or higher concentration. Thus, the relative areas for acetic acid were higher in V and L oils characterized with winey-vinegary defect (median of the defect = 1.7-3.8). Nevertheless, higher relative standard deviation (8.485) was found in a sample without this sensory defect, which shows the importance of the masking effect of other compounds when defining the sensory profiles of VOOs. The relative area of ethanol was also higher in oils with winey-vinegary defect. However, this compound is naturally present in VOO and is additionally produced by fermentation.