Role of botrytized grape micro-organisms in SO2 binding phenomena

Aims: The purpose of this work was to study the involvement of micro-organi sms, which develop together with Botrytis cinerea on grapes, in the SO2 bin ding power of musts. Methods and Results: Yeasts and bacteria were involved. Most bacteria were acetic acid bacteria, mainly of the Gluconobacter genus. Unlike oxidative y easts, Gluconobacter produce gluconic acid (in balance with delta -gluconol actone) from glucose, 5-oxofructose from fructose and dihydroxyacetone from glycerol. Production of carbonyl compounds from other sugars and polyols w as not detected or was very weak. Conclusions: Acetic acid bacteria are responsible for the increases in SO2 binding power of musts from botrytized grapes by oxidizing the three main s ugars of these grapes. Significance and Impact of the Study: Up to 80% of the SO2 binds with produ cts of Gluconobacter which easily grow an 'botrytized' grapes. Depending on climatic conditions, some vintages are particularly difficult to stabilize .