## 3 Results and Discussion
### Effect of Blending on the Total Phenolic Index and Low Molecular Weight Compounds Contents of WSs
Indeed, some authors described the relationship between phenolic acids and astringency as well as the relationship between their ethyl esters and astringency and bitterness [52; 53]. Furthermore, gallic and ellagic acids are well-known bioactive compounds, conferring antioxidant activity to the aged WS [54]. Figure 4 shows the ANOVA results for phenolic aldehydes levels of WSs according to the blending technology in each ageing technology. For all the phenolic aldehydes, no significant effect of the blending technology was found in WSs from both ageing technologies. Sinapaldehyde was the main compound of this group, followed by syringaldehyde, coniferaldehyde and vanillin, in the WSs produced. Higher levels were related to the alternative ageing technology compared with the traditional one: 54.09-59.24 vs. 17.16-25.08 mg/L for sinapaldehyde, 21.58-22.30 vs. 7.71-10.43 mg/L for syringaldehyde, 14.93-16.19 vs. 6.48-8.56 mg/L for coniferaldehyde, and 7.58-8.00 vs. 3.43-4.24 mg/L for vanillin. The highest levels observed in WSs resulting from the alternative ageing technology are in accordance with those determined during their ageing [14; 48]. Regarding the relation between these compounds, it should be highlighted that the syringyl-type aldehydes (sinapaldehyde and syringaldehyde) prevailed over the guaiacyl-type aldehydes (coniferaldehyde and vanillin), which was consistent with the corresponding ageing results. A similar pattern was also noticed in a recent work on the ageing chemistry [16], in which this behaviour was ascribed to the balance between additive and subtractive phenomena involving lignin and its derivatives, with oxidation reactions being of the utmost significance to explain the lower contents of coniferaldehyde and vanillin (more prone to oxidation than the syringyl-type aldehydes [55]). Figure 3: Average values of phenolic acids concentrations 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 (\(p>0.05\)). Since the natural blending did not affect the phenolic aldehydes contents, its suitability for the WS production process is strengthened. Actually, these compounds contribute to the WS flavour, particularly vanillin, which was positively correlated with the 'vanilla' aroma in WSs produced by the traditional ageing [4, 56] and by the alternative one [18], being a remarkable attribute of this spirit beverage and highly appreciated by consumers [57]. Besides, syringaldehyde acts as a bioactive compound [58] and may contribute to the pool of phenolic compounds whose intake, under moderate WS consumption, may have positive health effects [59], as opposed to the harmful effects induced by ethanol [60], thus enhancing the WS' added value. Concerning coumarins, the ANOVA results attained for the studied WSs (Figure 5) demonstrate that the blending technology had no significant effect on their contents. Quantitatively, scopoletin was the main compound of this group, as previously reported for WSs aged in barrels [4, 61]. Higher contents of scopoletin were observed in the WSs resulting from the traditional ageing technology (0.052-0.101 vs. 0.035-0.046 mg/L), whereas higher contents of umbelliferone were found in those resulting from the alternative one (0.00013-0.00026 vs. 0.00003-0.00015 mg/L), regardless of the kind of blending. These results suggest different  
Figure 4: Average values of phenolic aldehydes concentrations 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 (\(p>0.05\)). Figure 5: Average values of coumarins concentrations 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 (\(p>0.05\)).