## 3 Results and Discussion
### Statistical Analysis of the VOCs Profile in the Sabrina and Elide Strawberry Samples
#### 3.2.1 Linear Mixed-Effect Modelling (LME) on Elide Data Set  
The LME analysis conducted on the VOCs profiles of Elide discovered 40 VOCs differently expressed between PE and N5 mulching, 52 VOCs for the comparison of PE and N18, and 58 matching N5 and N18. In particular, out of 40 VOCs differently expressed between PE and N5 in Elide cv, 26 (E3, E9, E15, E16, E21, E24, E30, E32, E33, E35, Ald2, Ald4, Al1, Al3, Ac4, Ac5, Ac8, T3, T6, T8, F1-F3, L2, L3, and O1) presented amounts statistically  
Figure 1: Biplots of the PCA models for the two cultivars: Elide (R2 = 96.1%, panel **(A)**) and Sabrina (R2 = 98.4%, panel **(B)**); VOCs are reported as grey triangles. Figure 2: Heatmaps: Elide (panel **(A)**) and Sabrina (panel **(B)**). The colour scale ranges from blue, which indicates values lower than the median of the PE group, to red for values greater than the median of the PE group. higher in the fruit grown using N5 film, while 14 (E13, E17, E19, E20, E26, E27, E34, Ald1, Ald5, Ald6, Ac2, T1, T2, and T4) were more abundant in the strawberries produced on the PE much. The amount of the remaining 29 volatiles was comparable in both the treatments (PE and N5) (Figure 1; Table S1). Among the 26 volatiles characterizing Elide N5 fruit, some compounds, including methyl butyrate (E3), butyl acetate (E9), ethyl hexanoate (E15), hexyl butyrate (E24), benzaldehyde (Ald4), 2-methylbutanoate acid (Ac4), \(\alpha\)-terpineol (T6), mesifuran (F1), \(\gamma\)-decalactone (L2), and \(\gamma\)-dodecalactone (L3), exhibited a sweetness- and/or flavour-enhancing ability regardless of the sugar content, while isoamyl butyrate (E16) and 2-hexenal (Ald2) showed negative coefficients related to liking [10,17,18]. Moreover, some components, including hexanoic acid (Ac5), mesifuran (F1), furnaceol (F2), \(\gamma\)-decalactone (L2), \(\gamma\)-dodecalactone (L3), and several esters, such as methyl butyrate (E3), identified as key odorants to strawberry flavour, increased during the fruit ripening [18, 19, 20, 21]. In fruit, the enzymatic biosynthesis of volatile esters is due to the esterification of alcohols and acyl-CoA, derived from both fatty acid and amino acid metabolism, and occurs during the late steps of ripening [21]. In strawberries at an advanced degree of maturation, alcohol acyltransferase (AAT), the enzyme involved in the last step of ester formation, can display a 16-fold increase from the half-red to the full-red ripeness stage, and a statistical positive correlation occurs among the AAT gene expression, the AAT activity, and the content of some volatile esters [19]. Moreover, the availability of precursors is probably a limiting step in the biosynthesis of volatile esters, causing specific flavour profiles at different ripeness stages [19, 20, 21]. The formation of C6 aldehydes generally increases during ripening as a result of both the increment from 25 up to 200% in the activity of the enzymes lipoxygenase (LOX) and hydroperoxide lyase (HPL), which is involved in the biosynthetic pathway, and to the increase up to 200% of the substrate amount (linolenic acid) [20]. The contents of mesifuran (F1) and furaneol (F2) rise considerably during the strawberries' ripening, as the enzymes responsible for their synthesis, O-methyltransferasease for F1 and quinine oxidoreductase (FaQR) for F2, show the maximum activity at the full-red stage, allowing potential targets to engineer the strawberry flavour from breeding populations [19]. Among the 14 VOCs (E13, E17, E19, E20, E26, E27, E34, Ald1, Ald5, Ald6, Ac2, T1, T2, and T4) that are regularly more abundant in the Elide strawberries produced on PE with respect to N5, pentyl acetate (E13), hexyl acetate (E17), _cis_-3-hexen-1-ol-acetate (E19), _cis_-linalo oxide (T2), andlinalo (T4) are positively correlated to the taste sensation \"sweet\", while _trans_-2-hexen-1-ol-acetate (E20) exhibits strong negative correlations with both sweetness and consumers' liking [10,17].