INFLUENCE OF BOTRYTIS INFECTION OF THE GRAPES ON THE BIOLOGICAL AGING PROCESS OF FINE SHERRY

The high content in gluconic acid and glycerol produced because of Botrytis infection can affect biological aging of the wine. In aging, if wine's gluconic acid content is more than 600 mg/L, heterolactic fermentations appear with certain intensity, producing high concentrations of lactic acid and volatile acidity; this last parameter will affect the quality of the wine. Under normal conditions, for lower contents of gluconic acid, one does not observe any increase in volatile acidity, since the acetic acid which is formed is consumed in the metabolism of the florforming yeasts. The lactic acid existing in the wine is also metabolized by yeasts, reducing its content in the last phase of the biological aging. High glycerol content in must is also metabolized by yeasts to very low levels; in the final phase, "solera", one finds levels below 0.5 g/L.