Flor yeast metabolism in a model system similar to cellar ageing of the French "Vin Jaune": Evolution of some by-products, nitrogen compounds and polysaccharides

French flor-sherry wine "Vin Jaune" (Jura region) made from Savagnin grapes is aged under a film of Saccharomyces cerevisiae flor yeasts for 6 years a nd three months. During this ageing, velum develops and falls corresponding to yeast multiplication and autolysis, In a model system using glass recep tacles ("Fioles de Roux") containing sterilised Savagnin wine inoculated wi th a pure culture of S. cerevisiae flor yeast, the evolution of velum was s tudied for 15 weeks. At the same time, nitrogen compounds (amino acids, pep tides and proteins) and neutral polysaccharides were quantified in relation to glycerol, volatile acidity and acetaldehyde, Compounds such as glycerol , acetic acid and amino acids including proline are consumed by the flor ye asts whereas other compounds such as peptides and neutral polysaccharides a re released. At the same time, yeasts produce other compounds, namely aceta ldehyde.