A combination of biotechnology tools and coopers elements for an alternative the addition of SO2 at the end of the malolactic fermentation in red wines or at the “mutage” for the “liquoreux” wines

The grapevine is an important economical crop that is very sensitive to climate changes and microclimate. The observations made during the last decades at a vineyard scale all concur to show the impact of climate change on vine physiology, resulting in accelerated phenology and earlier harvest (Jones and Davis 2000). It is well-known that berry content is affected by the ambient temperature. While the first experiences were primarily conducted on the impact of temperature on anthocyanin accumulation in the grape, few studies have focused on others component of phenolic metabolism, such as tannins.

Vitis vinifera L. is the most widely cultivated Vitis species which includes numerous cultivars. Owing to their superior quality of grapes, these cultivars were long considered the only suitable for the production of fine wines. However, the lack of resistance genes in V. vinifera against major grapevine pathogens, requires for its cultivation frequent spraying with large amount of fungicides. Thus, the search for alternative and more sustainable methods to control the grapevine pathogens have brought the breeders to focus their attention on other Vitis species. In fact, wild Vitis genotypes present multiple resistance traits against pathogens, such as powdery mildew, downy mildew and phylloxera.

Condensed tannin is a principle group of polyphenol compounds derived from grape, greatly contributing to the bioactivity and the sensory perception of wine. Condensed tannins present as a heterogeneous mixture in nature involving various degrees of both polymerization and galloylation. Even though multiple attempts focusing on fractionation of grape condensed tannins by solid-phase have been conducted over the past decades, few individual tannins have been purified and identified. Hence, our knowledge on grape and wine condensed tannin moleculars has to be limited at the several known monomeric, dimeric and trimeric proanthocyanidins

The effectiveness of enzyme-mediated maceration processes in red winemaking relies on a clear picture of the target (berry cell wall structure) to achieve the optimum combination of specific enzymes to be used. However, we lack the information on both essential factors of the reaction (i.e. specific activities in commercial enzyme preparation and the cell wall structure of berry tissue). In this study, the different combinations of pure recombinant enzymes and the recently validated high throughput cell wall profiling tools were applied to extend our knowledge on the grape berry cell wall polymeric deconstruction during the winemaking following a combinatorial enzyme treatment design.

Proteins constitute one of the three main components of grape juice and white wine, phenolic compounds and polysaccharides being the others. A specific group of the total grape-derived proteins resists degradation or adsorption during the winemaking process and remains in finished wine if not removed by the commonplace commercial practice of bentonite fining. While bentonite is effective in removing the problematic proteins, it is claimed to adversely affect the quality of the treated wine under certain conditions, through the removal of colour, flavor and texture compounds. A number of studies have indicated that different protein fractions require distinct bentonite concentrations for protein removal and consequent heat stabilization.