Hormonal and associated metabolic changes in susceptible harvest-ripe grapes under asymptomatic and symptomatic Esca disease

Polyphenols are present in a wide variety of plants and foods such as tea, cacao and grape1. An important sub-class of these compounds is the flavanols present in grapes and wines as monomers (e.g (+)-catechin or (-)-epicatechin), or polymers also called condensed tannins or proanthocyanidins. They have important antioxidant properties2 but their biosynthesis remains partly unknown. Some recent studies have focused on the role of glycosylated intermediates that are involved in the transport of the monomers and may serve as precursors in the polymerization mechanism3, 4. The global objective of this work is to identify flavanol glycosides in grapes or wines, describe their structure and determine their abundance during grape development and in wine.

Usually the winemaker consider the grapeberry maturity as an actor of the wine quality. Grape seed are frequently used as a marker to assess the grape maturity. The first aim of this study is to obtain a better understanding of the impact of grape seed maturity on the grape seed and grape berry composition.

Alteration of sap pH is one of the first chemical changes that occurs within the xylem vessels of plants exposed to drought. Xylem sap acidification accompanied by the accumulation of soluble sugars has been recently documented in several species (Sharp and Davis, 2009; Secchi and Zwieniecki, 2016). Here, Vitis vinifera plants of the anysohydric cultivar Barbera were exposed to either short (no irrigation; SD) or to prolonged drought (continual reduction of 10% water; PD). When comparable severe stress was reached, the potted grapes were re-watered. SD was characterized by fast (2–3 days) stomatal closure and high abscisic acid (ABA) accumulation in xylem sap (>400 μg L−1) and in leaf. In PD plants, the rise in ABA levels was considerably diminished.

Atypical ageing (ATA) is a wine aroma fault occurring in white wines characterised by an early loss of varietal aroma as well as nuances of wet mop, acacia blossom, shoe polish and dirty rag among others. 2-aminoacetophenone (2AAP) – a degradation product of indole-3-acetic acid (IAA) – has been described as the major odour-active compound and chemical marker responsible for this off-flavour. Depending on the aroma intensity of wines, its odour threshold varies from 0.5 to 10.5 μg/L. It seems that a stress reaction in the vineyard triggered by climatic, pedological and viticultural factors can ultimately cause ATA development in wines and therefore shorten their shelf-life.

The movement of Natural wines has clearly increased in the last few years, to reach a high demand from consumers nowadays. Switzerland has not been left out of this movement and has created a dedicated association in 2021. This association has the ambition to develop a specific tasting sheet for natural wines. The study of the tasting notes shows that the olfactory description of wines is recent but predominant today. But wine is a product makes to be drunk and not (just) to smell it. Based on these findings, a new 100-point tasting sheet has been developed. The main characteristics are 1) an evaluation in the mouth before the description of the olfaction, 2) to give 50% of the points on the judgment for the mouth characteristics, 3) to pejorate the visual aspects only if the wine is judged as “not drinkable” and 4) to express personal emotions.