Background and Aims. If bioprotection has already been proven to limit the development of spoilage flora on musts, its effectiveness against oxidation depends on the winemaking process. To optimize its application, this study analyzed the evolution of the chemical composition of the bioprotected musts and wines, according to different settling routes. Their impacts on the organoleptic characteristics of wines were also studied. Methods and Results. A bioprotected must was subjected to 6 different maceration routes before AF (triplicates), varying the duration and temperature parameters. A temperature value ≤12°C was the main factor independently of the duration which allowed a good implantation of the bioprotectant. An increase of the maceration duration at 12°C led to browning of the must, without significant effect on the final color of the wine, which was felt as more “floral,” with more length in the mouth. Conclusions. The bioprotectant implantation and its effectiveness on the sensory profile of the wine was guaranteed at maceration temperature values lower than 12°C. Significance of the Study. This study participates in the improvement of the bioprotection management in white winemaking, with the guarantee of a positive impact of the prefermentation maceration without sulphites on the organoleptic profile of the wines.

Saccharomyces cerevisiae, as the workhorse of alcoholic fermentation, is a major actor of winemaking. In this context, this yeast species performs alcoholic fermentation to convert sugars from the grape must into ethanol and CO2 with an outstanding efficiency: it reaches on average 92% of the maximum theoretical yield of conversion. Primary metabolites produced during fermentation stand for a great importance in wine where they significantly impact wine characteristics. Ethanol indeed does, but others too, which are found in lower concentrations: glycerol, succinate, acetate, alpha-ketoglutarate... Their production, which can be characterised by a yield according to the amount of sugars consumed, is known to differ from one strain to another. S. cerevisiae is known for its great genetic diversity and plasticity that is directly related to its living environment, natural or technological and therefore to domestication. This leads to a great phenotypic diversity of metabolites production. However, the range of metabolic diversity is variable and depends on the pathway considered. In the aim to improve wine quality, the selection, development and use of strains with dedicated metabolites production without genetic modifications can rely on the natural diversity that already exists. Here we detail a screening that aims to assess this diversity of primary metabolites production in a set of 51 S. cerevisiae strains from various genetic backgrounds (wine, flor, rum, West African, sake...). To approach winemaking conditions, we used a synthetic grape must as fermentation medium and measured by HPLC five main metabolites. Results obtained pointed out great yield differences between strains and that variability is dependent on the metabolite considered. Ethanol appears as the one with the smallest variation among our set of strains, despite it's by far the most produced. A clear negative correlation between ethanol and glycerol yields has been observed, confirming glycerol synthesis as a good lever to impact ethanol yield. Genetic groups have been identified as linked to high production of specific metabolites, like succinate for rum strains or alpha-ketoglutarate for wine strains. This study thus helps to define the phenotypic diversity of S. cerevisiae in a wine-like context and supports the use of ways of development of new strains exploiting natural diversity. Finally, it provides a detailed data set usable to study diversity of primary metabolites production, including common commercial wine strains.