Polyphenols in kombucha: impact of infusion time on extraction and investigation of their behavior during “fermentation”

Teran is an important native variety grown in Istria known for its high level of polyphenols and intensive fruity character of wines. Teran’s yield and wine typicity have recently decreased due to climate changes (increased temperature and severe drought). Four drip irrigation treatments (25%, 50%, 75%, 100% of total evapotranspiration) and control were investigated for the influence on Teran yield and quality, where focus was given to the content and composition of main polyphenolic and volatile compounds in grapes. Irrigation positively influenced yield since the berry weight also increased with increased irrigation. This resulted in the highest yield for 100% ETc. The highest concentration of polyphenols had control, while the irrigation treatments did not differ significantly. However, there was a tendency to decrease concentration with increased irrigation probably due to the increased berry size, which led to a dilution effect. Regarding the volatile compounds, the most abundant group was alcohols, followed by acids.

The research is part of the “Ecovinegoals” project, financed by Interreg Adrion funds. It aims to encourage the adoption and dissemination of agroecological practices in intensive wine-growing areas. The study focuses on cost analysis of the wine-growing landscape enhancement in an organic winery in order to provide a useful tool for winemakers to direct their investments in green infrastructures. One of the Italian pilot areas of the Ecovinegoals project is the Venezia Biodistrict, characterized by viticulture in a flat reclamation area of 105,800 hectares.

The winegrowers of the intercommunal cooperative cellar of Saint Hilaire d’Ozilhan have been practicing terroir selection for ten years. Five years ago, after having equipped themselves with an efficient commercial structure, and anxious to improve knowledge of their terroirs and to better control quantitatively and qualitatively the range of typicality that they can develop, they asked the Syndicate Général des Vignerons Réunis des Côtes du Rhône and the Institut Coopératif du Vin to help them set up an approach to better judge the behavior of the Grenache and Syrah grape varieties in the different terroirs, then to enhance this work through the improving product quality.

Must clarification is an important step occurring just after grape extraction in the elaboration of white wine, consisting in a solid-liquid separation. Traditionally, low must turbidity, around 50-150 NTU, is generally reached in white winemaking in order to prevent reductive aromas and facilitating alcoholic fermentation. Alternatively, a higher turbidity (300 NTU or above) can be sought for reasons such as a better expression of grapes identity (terroir), or for getting a must matrix that could supposedly lead to wines having greater ageing potential.

Yield estimation is very important for the wine industry since provides useful information for vineyard and winery management. The early yield estimation of the grapevine provides information to winegrowers in making management decisions to achieve a better quantity and quality of grapes. In general, yield forecasts are based on destructive sampling of bunches and manual counting of berries per bunch and bunches per vine.