Bioprotection and oenological tannins association to protect Rosé wine color

Climate change is introducing a high variability on grape ripening, causing uncertainty, excessive spending on pesticides and eventually frustrating results in terms of the quality of the vintage, with the increasingly frequent appearance of aromatic problems associated with overripeness, raisining and greenness, which sometimes only appear in bottled wines.

Recent advances in phenomics and transcriptomics have the enhanced capacity for understanding how clonally propagated perennial crops like grapevines respond to their environments seasonally and over the course of multiple years. Because most grapevines are grafted, above-ground grapevine traits reflect scion genotype and its interaction with the local environment. In addition, traits expressed by the scion reflect rootstock genotype and how that rootstock is interacting with its environment seasonally and across years. To investigate rootstock x environment interaction on shoot systems in grafted grapevines we characterized comprehensive phenotypic variation in an experimental vineyard in Mount Vernon, Missouri, USA where the grapevine cultivar ‘Chambourcin’ is growing on its own roots and is grafted to three different rootstocks (‘1103P’, ‘3309C’, ‘SO4’).

Grapevine grafting is a complex process that since the establishment of phylloxera has become mandatory for grapevine. Grafting success in grapevine nurseries considerably varies among years and batches with most variety/rootstock combinations reach a high success rate (between 75% and 90%), but some combinations show lower success rates of around 40-50%. The causes of this variation are unknown, although biotic stresses like those caused by some viral infections have been demonstrated to affect the process. European certification schemes for the vegetative propagation of the vine include five major viruses (Arabis mosaic virus, Grapevine Fanleaf Virus, Grapevine Fleck Virus, and Grapevine-associated Leafroll Virus 1 and 3).

All along the red winemaking process, many microorganisms develop in wine, some being beneficial and essential, others being feared spoilers. One of the most feared microbial enemy of wine all around the world is Brettanomyces bruxellensis. Indeed, in red wines, this yeast produces volatile phenols, molecules associated with a flavor described as “horse sweat”, “burnt plastic” or “leather”. To produce significant and detectable concentrations of these undesired molecules, the yeasts should first grow and become numerous enough. Even if the genetic group of the strain present and the cellar temperature may modulate the yeast growth rate¹ and thus the risk of spoilage, the main factor seems to be the wines themselves, some being much more permissive to B. bruxellensis development than others.

Visual clarity in wines is crucial for commercial purposes [1]. Potential protein haze in white wines remains a constant concern in wineries, commonly addressed using bentonite [2].