Gluconic acid, its lactones, and SO2 binding phenomena in musts from botrytized grapes

Intramolecular gluconic acid esterification reactions led to the formation of two lactones, gamma- and delta-gluconolactone (glucono-1,4-lactone and glucono-1,5-lactone). The presence of the first has not yet been reported in must or wine. These lactones are in equilibrium with gluconic acid, gamma- and delta-gluconolactone representing, respectively, 5.8 and 4.1% of the acid level. Correlations between Must SO2 binding power, gluconic acid, and consequently its lactones are shown. The SO2 affinity of a mixture containing this acid and gamma- and delta-gluconolactone was determined, and gluconic acid appeared to be indirectly responsible for similar to8% of the bindable SO2 in musts from botrytized grapes.