## 3 Results and Discussion
### Effect of Blending on the Total Phenolic Index and Low Molecular Weight Compounds Contents of WSs  
The results displayed in Table 1 also show a non-significant effect of the blending technology on the TPI of these WSs. Slightly higher values were exhibited by the WSs produced through the alternative ageing technology than through the traditional one (55.86-63.37 vs. 28.91-31.38). Since TPI reflects the global content of phenolic compounds and furanic aldehydes of the aged WS [47], greater enrichment in these wood derived compounds was promoted by the former, demonstrating that the blending technology did not overlap with the ageing technology [14]. Figure 2 presents the ANOVA results for the total low molecular weight compounds concentration, determined by the HPLC method, of the WSs under study. The outcomes are coherent with those of total dry extract and TPI, confirming that the sum of phenolic compounds (phenolic acids, phenolic aldehydes, and coumarins) and furanic aldehydes concentrations found in the final products resulting from each ageing technology were not significantly influenced by the kind of blending. On the other hand, higher concentrations were associated with the alternative ageing technology (282.17-299.51 vs. 156.72-214.75 mg/L), which is also in agreement with previous reports on these WSs during the ageing process [14; 48]. Thus, these findings point to the natural blending as a suitable option to reinforce the sustainability of the production process of WSs, together with ageing in stainless steel tanks with wood staves inside and MOX. Specifically, the results of ANOVA for phenolic acids levels in the studied WSs (Figure 3) reveal that the differences in terms of gallic acid, syringic acid and ellagic acid between WSs obtained by natural blending and by the blending operation were not significant. Gallic acid was the most plentiful compound within this group of phenolic compounds, as observed during ageing, particularly in WSs that was in contact with chestnut wood [5; 14; 16]. Since our previous works [5] proved that chestnut wood is richer in gallic acid than Limousin oak, the result now obtained suggests that this kind of wood had a greater effect in the blends than Limousin oak wood, despite the same amount used (50:50 ratio). Interestingly, the wooden barrels (traditional ageing technology) afforded higher content of gallic acid to the WSs than the alternative technology (54.00-88.75 vs. 30.63-36.83 mg/L), regardless of the blending performed. Indeed, evidence exists that gallic acid is prone to oxidation [16; 49; 50], and oxidation reactions (subtractive phenomena) prevail over extraction and other additive phenomena, such as the gallotannins' degradation [51], during ageing through the alternative technology by supplying oxygen directly  
Figure 2: Average values of total low molecular weight compounds concentration of WSs from natural blending and from the blending operation in each ageing technology. Bars not marked with letters indicate non-significant differences between the average values (\(p>0.05\)). via MOX [14; 16]. Therefore, this chemical marker [5] persisted in the aged WSs, even after blending (natural or performed after ageing). Syringic and ellagic acids were more abundant in WSs resulting from the alternative ageing technology than from the traditional one (11.85-12.18 vs. 2.50-3.69 mg/L, and 14.75-15.33 mg/L vs. 7.68-9.37 mg/L, respectively), regardless of the blending technology. Similar behaviour was observed during their ageing process [14; 48]. According to studies addressing the role of oxidation reactions in the ageing chemistry [16; 51], staves combined with MOX induce more intense extraction of these compounds from the wood as well as degradation of their precursors--lignin for syringe acid, and ellagitannins for ellagic acid--(additive phenomena), but these acids are also less sensitive to oxidation than gallic acid [16]. The natural blending did not change the phenolic acids contents and their proportions, which are important features imparted by the ageing.