Further Studies on the Production of Natural, Sweet Table Wines from Botrytised Grapes

¹ Department of Viticulture and Enology University of California, Davis

During the 1956 season Semillon, Sauvignon blanc and White Riesling grapes were inoculated with the fungus Botrytis cinerea and after an incubation period were made into natural sweet table wines of 5.1 to 21.8 per cent sugar and 12.4 to 14.5 per cent alcohol. Spoilage from other microörganisms during botrytis growth was not a problem provided that the fruit was initially sound and uninjured. The drying rate of the botrytised fruit was closely related to incubation temperature, decreasing appreciably at temperatures below 68°F. Relative humidities of from 50 to 80 per cent had little effect on the drying rate.

The Balling-acid ratio of the treated must was inversely proportional to the total acid content of the fruit and was always greater than the ratio of the untreated must. The volatile acid content of the wines was correlated with the degree Balling of the treated must. The wines contained less than 0.1 per cent volatile acid when made from musts of less than 35 degree Balling. However, even a volatile acid content of 0.17 per cent was not objectionable, partially because the high sugar content in the wine masked its flavor.

Pilot-plant fasts in two wineries revealed no serious or inherent difficulties in commercial production of such wines. However, cost and consumer acceptance studies need to be made.