Changes in Volatile Profiles and Activity of Hydroperoxide Lyase and Alcohol Dehydrogenase During the Development of Cabernet Sauvignon Grapes (Vitis vinifera L.)

Abstract

In this study we focused on the development of Cabernet Sauvignon grapes and investigated changes in the activity of alcohol dehydrogenase (ADH) and hydroperoxide lyase (HPL) in different tissues. We sampled grape skin at four, six, seven, eight, nine, 10, 12, 14 and 16 weeks after anthesis; developing flowers when blooming at 0%, 5%, 50%, and 90%; and leaves at two and four weeks before anthesis and at two, four, six, eight, nine, and 10 weeks after anthesis. We also examined the type and fluctuation of volatile contents. ADH activity increased with the development of flowers and grape skins, which led to the increasing of types and concentration of alcohols. Low levels of 9-HPL led to low concentrations of C9 compounds. According to this paper, C6 compounds became abundant with the development of grape berries, while the activity of 13-HPL kept at a low level in the flowers and grape skins. There might have been a high level of 13-HPL activity from the end of flowering until fruit setting that we did not detect. Furthermore, similar C6 and C5 compounds were detected across all tissues, including hexanal, (E)-2-hexenal, (Z)-3-hexenal, (Z)-2-penten-1-ol, (Z)-3-hexen-1-ol, 1-hexanol and 3-hexen-1-ol. Generally speaking, the concentrations of C6 and C5 compounds could be used as the criterion of maturation of the three grape tissues.

Exploratory study of sugar andC6compounds in single berries of grapevine (Vitis viniferaL.) cv. Cabernet Sauvignon throughout ripening

“…The content of hexan-1-ol (Figure 3b) had the most marked increase starting around D3 when the berries changed colour, then peaked at D7 and strongly decreased in the majority of shrivelled berries. Similar results were reported by authors who tracked the changes of this compound across multiple stages of development of Cabernet Sauvignon grapes (Kalua and Boss 2009, Yang et al 2015. A lower concentration of hexan-1-ol was detected at the end of ripening compared to veraison for the grape cultivar Monastrell (Salinas et al 2004); despite this all of the authors were in agreement that a general increase of this compound started at the onset of veraison.…”

“…An inflection point for the trend line computed by local regression was found at around 15°Brix, which corresponded to the transition from D3 (pink/blush) to D4 (purple) (Figure S6). This sugar concentration is about the same TSS level of bunches at around 2 weeks post veraison (wpv) when ( E )‐2‐hexenal was found to peak in other studies (Salinas et al 2004, Kalua and Boss 2009, 2010, Yang et al 2015). By targeting berry development more precisely, we can speculate that berry development is a major determinant for the observed changes in ( E )‐2‐hexenal.…”

“…Salinas et al (2004) reported a decrease in ( Z )‐3‐hexen‐1‐ol in the grape cultivar Monastrell starting from 2 wpv. Results from Cabernet Sauvignon showed no changes of this compound (Kalua and Boss 2010) or a steady and significant increase during ripening (Kalua and Boss 2009, Yang et al 2015). Our findings, obtained using the stage of development scale rather than a time scale, suggest ( Z )‐3‐hexen‐1‐ol is synthesised after veraison and likely decreases at the end of ripening.…”

“…The content of (E)-2-hexenal declined afterwards and shrivelled berries contained a content of this compound similar to preveraison berries of the classes B0 and D1. There is general agreement in the literature (using random sampling strategies and multiple berry extracts) that the content of (E)-2-hexenal increases in red cultivars from pre-veraison until a few weeks post-veraison, then stabilises until harvest and finally decreases if berries are left on the vine beyond the commercial harvest date (Salinas et al 2004,Kalua and Boss 2009, Yang et al 2015. In Pinot Noir grape samples collected weekly from pea-size to harvest, the concentration of (E)-2-hexenal was found to be constant preveraison then increasing throughout the post-veraison period until harvest (Yuan and Qian 2016).…”

“…Aroma compounds of grape berries during ripening berries and the overall re-synchronisation obtained using a sequential targeted sampling strategy aimed to refine previous reports that were based on the analysis of composite samples of multiple asynchronous berries (Salinas et al 2004, Kalua and Boss 2009, Yang et al 2015, Yuan and Qian 2016. A summary of the changes in the mean content of C 6 compounds based on a developmental scale is also provided in the form of a heatmap of the relative abundance of each compound (Figure 4).…”