# Profiles of Volatile and Phenolic Compounds as Markers of Ripening Stage in Candonga Strawberries
## 3 Results and Discussion
### VOCs Compounds in Half-Red and Red Strawberries  
3.1 Comparative Determination of VOCs in the \"Candonga\" Strawberry Samples at Two Different Ripening Stages  
Overall, fifty-seven volatile compounds were identified by HS-SPME GC-MS analysis in the \"Candonga\" strawberry samples at two different ripening stages (half-red and red), and at three different harvest times which consisted of esters (26), aldehydes (5), alcohols (5), acids (9), terpen (5), furanones (3), lactones (3) and others (1). One-way ANOVA performed on the semi-quantitative data (RPA%) evidenced significant qualitative and quantitative changes in the profile of VOCs over the course of the two maturation stages, as reported in Table 3. On the other hand, Table S1 includes the abbreviation code, the experimental and literature Kovats indexes and the identification methods for the assigned VOCs. According to previous studies, ester compounds, responsible for the strawberry fruity and floral aroma, were the most abundant chemical class, with 18 and 26 different components accounting for about 37% and 49% of all the volatile compounds detected in the half-red and red fruit, respectively [3]. The majority of these esters have been previously reported in \"Candonga\" strawberries [28; 29]. The most representative esters in half-red strawberries were methyl butyrate (E2) (37%), methyl hexanoate (E9) (27%) and _trans_-2-hexen-1-ol acetate (E16) (20%), which increased up to about 40% of the total amount of esters in the red fruit. At ripening, together with \(\gamma\)-decalactone (L2), E16 became the component with the highest concentrations, individually constituting nearly 20% of the total content of the VOCs. These findings suggest that E16 and L2 could be considered as key indicators of full maturity in this variety (Table 3). Figure 2: RP-HPLC chromatograms of extracts from red (**left**) and half-red (**right**) “Candonga” strawberries. Numbers (1–8) above the peaks correspond, respectively, to the codes P1–P8 reported on Table 2.  
2-Hexenral Ald2 & 532.42 & a & 234.98 & b & *** & 503.36 & a & 221.54 & b & *** & 523.03 & a & 219.89 & b & *** \\ Nonanal & A43 & 29.57 & a & 2.22 & b & *** & 26.25 & a & 2.46 & b & *** & 26.75 & a & 2.64 & b & *** \\ Benzaldehyde & A41 & 76.65 & a & 51.2 & b & *** & 77.97 & a & 5.22 & b & *** & 77.14 & a & 5.37 & b & *** \\ Dodecanal & A45 & 8.24 & a & 3.42 & b & *** & 8.08 & a & 3.66 & b & *** & 8.14 & a & 3.60 & b & *** \\
1-Hexanol & A11 & 209.84 & a & 27.21 & b & *** & 209.38 & a & 28.10 & b & *** & 215.02 & a & 27.69 & b & *** \\ _trans-3-Hexen-1-ol & A12 & 11.12 & a & 2.02 & b & *** & 11.08 & a & 2.11 & b & *** & 11.89 & a & 2.18 & b & *** \\ \hline \hline \end{tabular}
\end{table}
Table 3: Volatile compounds obtained in strawberries cv ”Sabrosa” at two different ripening stages (half-red or red) and at three harvest times (H1, H2, H3). Butyl acetate (E6), methyl pentanoate (E7), ethyl pentanoate (E8), butyl butyrate (E10), ethyl hexanoate (E11), isoamyl butyrate (E12), octyl isobutyrate (E23) and octyl 2-methylbutyrate (E24) were detected only in red berries (Table 3). In fruit, enzymatic biosynthesis of volatile esters through the esterification of alcohols and acyl-CoA, derived from both fatty acid and amino acid metabolism, occurs during the late ripening steps [30]. The enzyme responsible for the final step of ester formation is alcohol acyltransferase (AAT), which in strawberries can exhibit a 16-fold increase from the half-red to the full red ripeness degree [31]. A consistent correlation occurs among the expression of an AAT gene, AAT activity and concentrations of some volatile esters [31]. The availability of substrates for the biosynthesis of volatile esters is believed to be a limiting step in the production of esters, leading to different flavor profiles at each ripeness stage [30; 31; 32]. Five aldehyde compounds were common to the half-red and red stages, although occurring at a significantly higher concentration in full red berries (Table 3).