Impact of nitrogen addition timing on the synthesis of fermentative aromas in alcoholic fermentation

Quantity and quality of flavonoïds in grape berries are important parts of their global quality. Several studies had shown that tannins are responsible for some major flavour properties of red wines such as colour, bitterness and astringency. Nevertheless, their synthesis and properties are still misunderstood. Some studies had suggested that the tannic pool was set before veraison. Thus, the comprehension of the relations between environment and setting of this tannic pool, up to the harvest, is not sufficient.

New grape varieties with several resistance loci towards powdery and downy mildew allows to significantly reduce the use of fungicides

Vegetative propagation of grapevines can generate spontaneous somatic variations, providing a valuable source for cultivar improvement. In this context, natural variation in the composition of phenolic compounds in grapevine berries and seeds stands as a pivotal factor in crafting wines with diverse oenological profiles from the same cultivar. To deepen on the understanding of the physiological and genetic mechanisms driving somatic variation in grape phenolics, here we characterized a somatic variant from Tempranillo Tinto, the clone VN21, that exhibits an intense reduced berry skin cuticle and increased extractability of phenolic compounds during wine fermentation.

Light-struck taste (LST) is a wine fault that can occur in white and sparkling wines when exposed to light. This defect is mainly associated to the formation of methanethiol and dimethyl disulfide due to light-induced reactions involving riboflavin (RF) and methionine [1]. The presence of RF in wine is mainly due to the metabolism of yeast [2] which fermenting activity can be favoured by using yeast derivative products (YDPs) as nutrients. Nonetheless, a previous study showed the addition of YDPs before the alcoholic fermentation (AF) led to higher concentrations of RF in wines [3]. Due to the widespread use of YDPs in the winemaking process, this study aimed to understand the possible relation between the content of RF in wine and the YDP adopted as nutrient for AF.

A Syrah/R99 vineyard in the Stellenbosch area was used. The vineyard is vertically trained and spaced 2.75 x 1.5 m in north-south orientated rows on terroir with Glenrosa soil and west-facing slope. Irrigation (to 100% field water capacity) treatments were applied at different development stages [all stages (including berry set stage); pea size; véraison; post-véraison]. Combined effects of water status and ripeness level were investigated. Preliminary results are presented.