## 3 Results and Discussion  
In the present work, the effect of the presence of Strecker aldehydes (released as a consequence of the depletion of sulphur dioxide) on the quality perceived by a group of Spanish technical experts in two different wine contexts has been evaluated. Further, the effect of different commercial resins on the elimination of these oxidation-related aldehydes has been tested. Sensory Significance Derived from the Release of Strecker Aldehydes from Hydroxyalkylsulfonate Adducts  
Strecker aldehydes in wine can be found in their free form, which is volatile and can be orthonasally perceived, or in their adduct form with SO\({}_{2}\) (hydroxyalkylsulfonate), which is non-volatile and cannot be sensory perceived. In fact, it has been reported that non-oxidised commercial wines contain a pool of powerful oxidation-related Strecker aldehydes (from 33 to 96%) that are released back into their free volatile form when free SO\({}_{2}\) disappears [8]. However, the concentration of Strecker aldehydes that are detrimental to wine aroma quality has not been studied yet. The quality scores given by the panel of experts for the six samples in each of the contexts indicates that the quality varies significantly (\(p<0.001\)) with the level of aldehydes in both contexts. As can be seen in Figure 1, the increase in the concentration of aldehydes (from level 1 to level 6) causes a significant decrease in the perceived aroma quality in both contexts. In young wines, the release of Strecker aldehydes decreases orthonasal quality by between 27-40% and in oaked wines by 36-47% in both cases for the three aldehyde categories. As can be seen in Figure 1, in both wine models, the maximum drop in quality is found from level 4. This implies that at the beginning of the shelf life of a wine (i.e., low levels of free aldehydes: levels 1-3), the initial concentration of free aldehydes regardless of the total amount of aldehydes (low, intermediate or high category) is at levels low enough to be hardly sensory perceived resulting in an absence of significant decrease in wine quality perception, according to the panel of wine experts. On the contrary, the ageing process (levels 4-6), with its implicit loss of SO\({}_{2}\), causes the amount of free aldehydes to increase and thus to be sensory perceived resulting in a significant wine quality decrease. Table 4 shows the decrease in quality scores due to the release of the free forms of aldehydes for similar theoretical levels of total aldehydes (e.g., high category: average  
Figure 1: Average aroma quality for different levels of aldehydes. **(a)** Young wine model (**b**) Oaked wine model. Different letters within the same graphic indicate significant differences (\(p\leq 0.05\)). Error bars are calculated as sd/n\({}^{0.5}\); sd: standard deviation; \(n\): number of panellists. quality score for the level 6 minus level 3 = \(-\)3.8 for the young wine). As it was expected, the panel of experts punishes the increment more in aldehyde concentration due to the simulation of the release of aldehydes from the breakdown of the aldehyde-SO\({}_{2}\) adducts in wines with high amounts of total aldehydes (level 3 and level 6) compared to wines with low amounts (level 1 and level 4) (in both contexts). However, comparing the same aldehyde category in both wine models, quality depreciation was only significant for the lower aldehyde concentration (\(p\leq 0.001\)), being more pronounced for oaked wines. Figure 2 shows the spider graphs representing the citation frequencies of the attributes related to high quality or low quality in each wine context exemplars. In concordance with these frequencies, young wines with high quality would be mainly related to fruity aromas (Figure 2a), while low quality would be driven by descriptors such as cooked vegetables and oxidation-related attributes (Figure 2c).