Studies in the Commercial Production of Natural Sweet Wines from Botrytised Grapes

¹ Department of Viticulture and Enology, University of California, Davis
² Cresta Blanca Winery, Livermore, California

Commercial natural sweet wines of high quality have been produced from grapes harvested when mature and sound, then inoculated with the spores of Botrytis cinera, and held on trays under controlled environmental conditions until crushed. Laboratory techniques in handling the inoculum and fruit were modified to accommodate three tons of fruit at one time. The amount of fruit must be matched to the capacity of the environmental control facilities for close control of temperature, relative humidity, and air velocity during the infection and incubation. A closed system using refrigeration for dehumidification minimizes the danger of activity of undesirable organisms. The musts should be fermented at low temperatures for close control of volatile acid content and stabilization at the desired balance of sugar and alcohol. The wines were easily stabilized at about 13 percent alcohol and 10 degrees Balling by the use of refrigeration and the addition of sulfur dioxide. Neither the sulfur dioxide nor the volatile acid content had an adverse effect on aroma and flavor. The volatile acid content of the wines remained under 0.1 percent if the must did not exced 35° Balling.