Amino nitrogen content in grapes: the impact of crop limitation

Climate change and harvest date decisions have led to the evolution of must quality over the last decades. Increases in must sugar concentrations are among the most obvious consequences, quantitatively. Saccharomyces cerevisiae is a robust and acid tolerant organism. These properties, its sugar to ethanol conversion rate and ethanol tolerance make it the ideal production organism for wine fermentations. Unfortunately, high sugar concentrations may affect S. cerevisiae and lead to growth inhibition or yeast lysis, and cause sluggish or stuck fermentations. Even sublethal conditions cause a hyperosmotic stress response in S. cerevisiae which leads to increased formation of fermentation by-products, including acetic acid, which may exceed legal limits in some wines.

Although there are detailed studies on the microbiota of Vitis vinifera L. grapes, little is known about the diversity of yeast communities present in non-vinifera Vitis ecosystems (i.e., grapes and spontaneously fermenting grape musts). Potentially scientific and/or enological valuable yeast strains from these non-vinifera Vitis ecosystems might never be isolated from V. vinifera L. Using a standard culture-dependent strategy, we studied the population of yeast species during initial stages of spontaneous fermentation of V. labrusca L. (Isabella) grape musts. Rare non-Saccharomyces yeast species were recognized in Isabella, including Candida azymoides, Pichia cecembensis, Candida californica, Candida bentonensis, Issatchenkia hanoiensis and Candida apicola.

Glutathione plays a key role in preventing some oxidative processes during winemaking. This molecule limits the must enzymatic oxidation, reacts with caffeic acid and generates a colourless compound that prevents subsequent browning. It also has a protective effect on wine aroma, preventing the oxidation of the volatile compounds with a high sensory impact.

Vine growers face an increasing number of decisions, both tactical and strategic, in a context where available data and constraints are on the rise, such as resources, societal, environmental, climatic, and economic factors. This has led to a growing supply of decision support systems (DSS) and softwares to manage vineyards. Facing this new complexity, growers must now consider several options: giving up the use of DSS, using systems that are compatible with each other but may limit their options, or using a single system that may be too complex to use effectively. In this context, itk has expanded its Vintel® tool, which was originally designed for grapevine water status management (irrigation, inter-row, cover-crop, etc.), to include fertilization and disease management.

Cabernet Sauvignon grapes from recently planted vines in Santa Catarina State (Brazil), were sampled during ripening from the 2005 and 2006 vintages.