Evolution of green leaf volatile profile and aroma potential during the berry development in five Vitis vinifera L. Cultivars.

Green leaf volatiles (GLVs), play important roles in the green and fresh aroma characteristics of grape berries. The evolution of GLV profiles regarding the varietal difference during grapevine phenological ripening is not well understood. This study generated the GLV profiles of five Vitis vinifera L. cultivars ('Cabernet Sauvignon,' 'Cabernet Franc,' 'Cabernet Gernischt,' 'Chardonnay,' and 'Sauvignon Blanc') at five ripening stages. GLVs were distinctive at different E-L stages for each grape variety. (E)-2-hexen-1-ol, 1-hexanol, and hexanal were the dominant components in all mature berries. In terms of total GLV content, all varieties reached the maximum at maturity in the 2019 vintage, and the total GLV content was higher in mature Sauvignon Blanc and Cabernet Sauvignon grapes. In the 2020 vintage, the total GLV content in Chardonnay and Sauvignon Blanc berries rapidly accumulated at veraison and peaked before harvest. The present results could help winemakers create a good balance of wine aroma.

Dynamic changes in monoterpene accumulation and biosynthesis during grape ripening in three Vitis vinifera L. cultivars.

Monoterpenes are important aroma components in grapes and wines. We analyzed the free and bound monoterpene profiles and the transcript levels of terpenoid biosynthesis genes in Vitis Vinifera cvs. Muscat Hamburg, Riesling, and Sauvignon Blanc grapes at five ripening stages. Principal component analyses revealed that the three cultivars had different free monoterpene profiles at harvest and the early stage of ripening. In all cultivars, the total bound monoterpene contents were higher than the free monoterpene contents during grape ripening. The changes in monoterpene profiles in different grape varieties were correlated with the transcript levels of some VviTPS and VviGT genes. In Riesling, the VviGT14 and VviUGT88A1L1 transcript levels were related to geraniol glucoside accumulation. In Muscat Hamburg, the VviPNLGl1, VviPNLGl2, and VviPNLGl4 transcript levels were related to linalool accumulation. Understanding the dynamic changes in monoterpene accumulation and biosynthesis will allow winemakers to devise strategies to improve grape and wine aromas.

Effect of cluster zone leaf removal on monoterpene profiles of Sauvignon Blanc grapes and wines.

Monoterpenes contribute to the varietal aromas of grapes and wines. We determined the effects of cluster zone leaf removal on the monoterpene profiles of Sauvignon Blanc grape berries and wines, and on the expression of key genes in the terpenoid pathway. Leaf removal at two intensities (half basic, 50%; full basic, 100%) was conducted at two weeks before veraison, veraison, and two weeks after veraison. Half basic leaf removal increased the pH and decreased the tartaric acid content in grapes and wines. The concentrations of most free- and bound-form monoterpenes in grapes were increased by early leaf removal. The total monoterpene contents were increased in wines in the defoliation treatments, but were significantly lower in wines from the full basic leaf removal treatments than in wines from the half basic leaf removal treatments. The defoliation treatments resulted in increased transcript levels of some key genes in terpene biosynthesis (VvPNLinNer1, VvPNLinNer2, VvPNLNGl1, VvPNLNGl2, and VvUGT88A1L1).

Sensory approach and chiral analysis for determination of odour active compounds from feijoa (Acca sellowiana).

The odour-active compounds of feijoa (Acca sellowiana), were isolated by Solvent-Assisted Flavour Evaporation (SAFE). By application of GC-O and the aroma extract dilution analysis (AEDA), nineteen odorants were detected. Volatile compounds with highest flavour dilution (FD) factor were quantified by internal standard and relative response factor. On the basis of the quantitative data and odour thresholds in water, odour activity values (OAV) were calculated. High OAVs were determined for ethyl butanoate, Z-3-hexenal, linalool and methyl benzoate responsible for the fruity, green, flowery and medicinal notes. A recombination assay and omission tests, showed the relevance of Z-3-hexenal, linalool and methyl benzoate as odour active compounds in feijoa aroma. Headspace solid-phase microextraction (HS-SPME) was used in order to verified linalool enantiomeric distribution in two feijoa varieties. R-linalool was the major configuration in both varieties. Quimba variety showed an enantiomeric ratio 75:25 while for Mammoth variety, linalool enantiomeric ratio was 95:5 (R:S).