EFFECT OF MANNOPROTEIN-RICH EXTRACTS FROM WINE LEES ON PHENOLICCOMPOSITION AND COLOUR OF RED WINE

In the last decades the use of bioestimulants in viticulture have been promoted as alternative to conven- tional pesticides. Moreover, as bioestimulants promote the biosynthesis of secondary metabolites in grape berries, several studies had investigated their influence on the accumulation of phenolic com- pounds (Monteiro et al., 2022). However, few studies, so far, are focused on the accumulation of the vo- latile compounds and their impact on the produced wines (Giménez-Bañón et al., 2022; Gomez- Plaza et al., 2012; Ruiz Garcia et al., 2014).
This study was conducted in a single vineyard of white autochthonous grapevine variety Savvatia- no (Vitis vinifera L.) in Muses Valley (Askri, Viotia, Greece). Chitosan (CHT), Abscisic Acid (ABA) and Benzothiadiazole (BTH) were applied.

Yeast cell walls (CWs) may adsorb wine components with a significant impact on wine quality. When dealing with red wines, this adsorption is mainly related to physicochemical interactions between wine polyphenols and cell wall mannoproteins. However, mannoproteins are a heterogeneous family of complex peptidoglycans including long and highly branched N-linked oligosaccharides and short linear O-linked oligosaccharides, resulting in a huge structural diversity.

Sforzato di Valtellina DOCG is a special dry red wine produced from partially dehydrated Nebbiolo wine-grapes growing in the Rhaetian Alps valley of Valtellina (Lombardy, Italy). Valtellina terraced vineyards are located at an altitude of 350–800 m according to ‘heroic’ viticulture on steep slopes. The harvested grape bunches are naturally dehydrated indoors, where a slow and continuous withering occurs (about 20% w/w of weight loss), until at least 1st December when the grapes reach the desired sugar content and can be processed following a normal winemaking with maceration.

Nowadays, the rapid growth of vineyards with organic practices and the use of copper as the only fun-gicide against downy mildew raises again the question of the effect of copper on varietal thiols in wine, especially 3-sulfanylhexan-1-ol (3SH) and its acetate (3SHA). A few decades ago, several works indicated that the use of copper in the vineyard had a negative effect on the content of varietal thiols in Sauvignon blanc wines [1, 2]. However, these studies only considered the concentration of the reduced form (RSH) of varietal thiols, without quantifying the oxidised ones. For this purpose, we proposed to monitor both reduced and oxidised forms of varietal thiols in wine under copper stress during alcoholic fermentation to have a more complete picture of the biological and chemical mechanisms.

Grape (Vitis vinifera) is one of the world’s oldest agricultural fruit crops, grown for wine, table grape, raisin, and other products. One of the factors that can cause a reduction in the grape growing area is temperature rise due to climate change. Elevated temperature causes changes in grapevine phenology and fruit chemical composition. Previous studies showed that grape varieties respond differently to a temperature shift of 1.5°C; few varieties had difficulties in the fruit development or could not reach the desired Brix level.