Role of botrytized grape micro-organisms in SO₂binding phenomena

Abstract

Aims: The purpose of this work was to study the involvement of micro-organisms, which develop together with Botrytis cinerea on grapes, in the SO 2 binding power of musts. Methods and Results: Yeasts and bacteria were involved. Most bacteria were acetic acid bacteria, mainly of the Gluconobacter genus. Unlike oxidative yeasts, Gluconobacter produce gluconic acid (in balance with d-gluconolactone) from glucose, 5-oxofructose from fructose and dihydroxyacetone from glycerol. Production of carbonyl compounds from other sugars and polyols was not detected or was very weak. Conclusions: Acetic acid bacteria are responsible for the increases in SO 2 binding power of musts from botrytized grapes by oxidizing the three main sugars of these grapes. Signi®cance and Impact of the Study: Up to 80% of the SO 2 binds with products of Gluconobacter which easily grow on`botrytized' grapes. Depending on climatic conditions, some vintages are particularly dif®cult to stabilize.

Metschnikowia Strains Isolated from Botrytized Grapes Antagonize Fungal and Bacterial Growth by Iron Depletion

“…Many hyphae lysed at the tip, and in others extensive protoplasmic coagulation occurred. Forty- 3 and then flooded with Botrytis conidia. The greater the amount of iron added, the narrower the halos and inhibition zones were (Table 2).…”

Yeast Diversity and Persistence in Botrytis-Affected Wine Fermentations

“…During the fermentation of botrytis-affected musts, the indigenous bacteria and non-Saccharomyces yeast populations decrease as Saccharomyces species dominate (18,28). By their nature sweet wines possess residual sugar, and thus fermentations are prematurely stopped, often by judicious use of SO 2 . Recently the production of gluconic acid, 5-oxofructose, and dihydroxyacetone by the acetic acid bacteria in botrytis-affected musts was shown to reduce the effective concentration of SO 2 , making these wines more difficult to stabilize against further microbial growth (2).…”

Microbial Succession in Spontaneously Fermented Grape Must Before, During and After Stuck Fermentation

“…Interestingly, in both years Gluconobacter cerinus was isolated during the whole fermentation period. Its presence was also described in botrytised wines by Barbe et al (2001). Lactic acid bacteria are known to be found in must and wine due to their tolerance of acidic conditions and ethanol.…”