## 3 Results and Discussion
### Building a Formulation as RM for the Winey-Vinegary Defect  
As a first step, the chromatograms of oils with winey-vinegary defect were examined to identify the most relevant volatile compounds. Figure 3 shows the chromatogram of a VOO that was qualified with a medium-high intensity (Md = 5.7) of vinegar-winey defect by sensory laboratories. There were 7 major and most characteristic volatiles, although only three (ethyl acetate, ethanol and acetic acid) explain the vinegar-winey defect. These volatiles were selected as \"primary compounds\" for this sensory defect since they smell sticky, alcohol/spicy/winey, and vinegar, respectively [40]. The other four (hexanal, _E_-2-hexanal, 1-hexanol, _E_-3-hexen-1-ol) contribute to cut grass/green sensory perception, a perception that is present in all VOOs at different levels of intensity. The first conclusion is that none of the three \"primary volatiles\" selected for vinegar aroma in VOOs do not necessarily smell like the sensory defect by itself, although their aroma partially resembles sensory notes perceived in winey-vinegary oils. They are considered volatile markers because they are always present when the aroma is perceived (Table 2), and furthermore there is a causal relationship between the intensity of the vinegar aroma and the concentration of the marker. Thus, the final aroma of a VOO qualified with the winey-vinegary defect results from the presence of its volatile markers in combination with others. Thus, reproducing the aroma of the winey-vinegary aroma in VOOs is not as easy as adding volatiles to a refined olive oil. On the contrary, it requires studying the aroma-aroma interaction in the process of flavor matching to reproduce the aroma of a RM. Thus, when mixing volatile compounds to formulate a RM, the resulting aroma should be perceived with a holistic perception (a single aroma), just as it occurs in a real VOO, instead of an analytical perception (several aromas mixed that can be identified in the mixture). To create the first formulation, the seven volatile compounds were first diluted to 300 mg/kg and the concentrations were reduced/increased to reach the intensity levels found in a real VOO. The final concentrations were as follows: ethyl acetate (80 mg/kg), ethanol (600 mg/kg), acetic acid (40 mg/kg), 1-hexanol (20 mg/kg), and \(E\)-3-hexen-1-ol (40 mg/kg). Hexanal and \(E\)-2-hexenal were initially excluded, since they gave rise to an aroma similar to 1-hexanol and \(E\)-3-hexen-1-ol and would be included in further steps if the optimization of the formulation required adding new compounds to provide green aroma. The mixture of these compounds provided the first formulation, coded as AV1 (Table 3). The first conclusion was that the aroma as perceived by assessors was not homogeneous. The initial formulation AV1 was characterized by a slightly vinegary aroma, although the assessors reported sweet sensory notes (two assessors) and a slight rancid odor (three assessors). After obtaining individual opinions from assessors, it was decided to modify the composition before submitting the formulation to the modified simplex. In particular, the concentrations of the volatiles responsible for sensory defects (ethyl acetate, ethanol, acetic acid) was increased with the aim of producing an aroma that all the assessors would relate with winey-vinegary defect. Thus, acetic acid and ethanol were diluted to 600 mg/kg and ethyl acetate to 200 mg/kg. However, the assessors unanimously qualified this aroma as \"chemical\" and \"non-natural\", and it was therefore decided to increase the concentrations of the compounds producing green/fruity aroma (hexanal, \(E\)-2-hexenal, \(1\)-hexanol, \(E\)-3-hexen-1-ol) to obtain a \"green base aroma\" that reminds of VOO. Figure 3: Chromatogram of a VOO qualified with an intensity (median of the defect) of 5.9 of the winey-vinegary aroma defect.