Assessing reserve nitrogen at dormancy for predicting spring nitrogen status in Chardonnay grapevines

Improving our knowledge on biotic and abiotic factors that influence the composition of the grapevine mycobiome is of great agricultural significance, due to potential effects on plant health, productivity, and wine characteristics. Among the various environmental factors affecting the morphological, physiological, biochemical and molecular attributes of grapevine, drought stress is one of the most severe, becoming increasingly an issue worldwide.

Red grape pomace, a waste from wine production, can be valorised by extracting polyphenols, high-added value compounds used in cosmetics or oenology. For use at an industrial level, using green extraction techniques, pomace need to be stored before being processed. The aim of this study is to test various storage conditions in order to maintain high level of polyphenols over 180 days, while keeping storage cost economically interesting. In a first step, different storage conditions (ambient temperature or cooled (4°C) temperature, anaerobic (saturation with N2) or aerobic conditions, and addition of sulphur dioxide (SO2)) were compared on small samples (1 kg) packed in plastic pockets. The quality of storage was assessed by following the optical density of the pomace extract at 280 nm (DO 280 expressed as mg/l eq gallic acid), which is an indication of the amount of remaining extractable polyphenols.

Prematurely aged red wines are marked by intense prune and fig aromatic nuances that dominate the complex bouquet that can be achieved through bottle aging.

The bioprotection of musts or grapes is a strategy for limiting sulfiting during winemaking and more specifically at pre-fermentative step. The most preconized yeasts in bioprotection mainly belong to Metschnikowia pulcherrima and Torulaspora delbrueckii species. While previous studies have demonstrated that bioprotectant non-Saccharomyces strains were able to protect musts and wines against microbial spoilage as well as sulfites, they cannot protect must against oxidation which appears to be the main limit of this practice.

Oenococcus oeni is the main Lactic Acid Bacteria responsible for malolactic fermentation, converting malic acid into lactic acid and carbon dioxide in wines. Following the alcoholic fermentation, this second fermentation ensures a deacidification and remains essential for the release of aromatic notes and the improvement of microbial stability in many wines. Nevertheless, wine is a harsh environment for microbial growth, especially because of its low pH (between 2.9 and 3.6 depending on the type of wine) and nutrient deficiency. In order to maintain homeostasis and ensure viability, O. oeni possesses different cellular mechanisms including organic acid metabolisms which represent also the major pathway to synthetize energy in wine.