# Early Basal Leaf Removal at Different Sides of the Canopy Improves the Quality of Aglianico Wine
## 3 Results and Discussion
### Volatile Organic Compounds  
Using HS-SPME-GC-MS analysis, a total of 41 volatile compounds were identified and grouped according to the following chemical groups (Table 4): acids (6), alcohols (7), esters (19) and others (9). Briefly, the levels of all VOCs strongly differentiated the season samples (\(p<0.001\)). The total VOC content was found to be lower in 2017 and 2018 than in 2016 (about \(-25\%\) and \(-49\%\), respectively). Among the volatile compounds, alcohols comprised the largest group, accounting for 68% of the total in 2016 and 2017 and about 84% in 2018. The second most abundant group was that of esters, which accounted for about 30% in 2016 and 2017 and about 14% in 2018. The other groups were detected at very low levels (1.1-1.4% for acids and \(<\)1% for others). It is well known that alcohols are recognizable by their strong and pungent smell and taste [39]. Among this group, 3-methyl-1-butanol (responsible for solvent and fused notes) was the most abundant in all the wines, although the concentrations found were always below its odor threshold (30,000 ug/L) [40]; thus, it likely did not contribute to wine aroma. The second major alcoholic compound was 2-phenylethanol--responsible for honey, spice, rose and lilac notes--found at concentrations above its odor threshold (750 ug/L) [41]; consequently, this compound may have contributed to the aroma of the wines. Concerning esters, diethyl malate, responsible for over-ripe, peach and cut grass odors [42], was the most abundant (148.6-1248.1 ug/L), followed by ethyl octanoate (245.3-775.3 ug/L) with sweet, fruity and pear odors; ethyl acetate (113.1-261.2 ug/L) with pineapple, fruity and solvent odors; ethyl hexanoate (102.6-354.5 ug/L) with fruity, green apple, brandy and wine-like notes; isoamly acetate (29.1-142.0 ug/L) with banana, fruity and sweet odors; and ethyl decanoate (49.1-116.3 ug/L) with fruity and grape odors [43]. Other esters were present at lower concentrations. Concerning acids, the most abundant was octanoic (42.9-62.6 ug/L), characterized by fatty and rancid notes [43], followed by acetic (9.8-17.6 ug/L) with a pungent and vinegar odor [42], decanoic (9.1-14.0 ug/L) with fatty and rancid notes [43] and hexanoic (2.5-11.7 ug/L) characterized by cheese and fatty notes [43]. However, the concentrations of all these acids were below their odor thresholds and, consequently, they likely did not contribute to the aroma of the wines. Among the other volatiles, sulfur compounds (methanol, ethyl methylhiopropanoate and ally isothianate), terpen (\(\alpha\)-terpineol and 4-terpineol), 4-ethylphenol, 2-octanone, nonanal and ethyl 2-fluoroate were identified. All these latter compounds were found at concentrations below their odor thresholds. The removal of basal leaves influenced the volatile compounds in the wines to a lesser extent than the season. In comparison to the control samples, leaf removal led to a decrease in total volatiles of about 18%, 13% and 14% for defoliation at the north, south and north-south canopy sides, respectively. Concerning the most quantitatively representative group, leaf removal led to a decrease in total alcohols of about 17%, 13% and 11% for north, south and north-south, respectively. A major decrease was observed for 3-methyl-1 butanol and 2-phenylethanol, whereas a slight increase was found for 1-hexanol and benzyl alcohol. A decrease due to leaf removal was also observed for ester compounds and was more pronounced on the north and south sides (\(-16\%\) for south and \(-25\%\) for north and north-south, respectively). Almost all ester compounds contributed to this decrease, except for ethyl lactate in the three defoliated treatments, ethyl 2-methylbutyrate and isoamyl acetate in the vines defoliated on the north side, and butyl formate in the vines defoliated on the north and south sides. Defoliation at the south and north-south sides also led to an increase in acids (+21% and +15%, respectively).