Many sweet and dessert wines are made from grape juice with sugar concentrated by partial drying, freezing, botrytis infection and late harvesting, according to UC viticulture specialist Matthew Fidelibus, a conference organizer.

Fidelibus researches winegrape cultivars best suited for the San Joaquin Valley of California at the UC Kearney Agricultural Research and Extension Center near Parlier, where the weather is quite different from the storied wine production locales in Napa and Sonoma counties.

Fidelibus’ interest in sweet wine was piqued in 2008 by an unplanned, but fortuitous experiment with Diamond muscat raisin grapes. Fidelibus was researching a labor-saving process for drying raisins, called dried-on-the-vine.  Instead of putting grapes on paper trays between vineyard rows, the producer cuts the grapes’ stems and leaves the clusters to dry in the canopy, where they can later be harvested mechanically.

Sometimes, however, cool temperatures early in the fall prevent the grapes from drying adequately. Such was the case with the Diamond muscat grapes. The weather that year left Fidelibus with a supply of partially dried, withered grapes. Fidelibus shipped them to enologists in Davis to be made into wine.

“It was really delicious sweet wine,” Fidelibus said. “It started me thinking, maybe we should be studying grapes intended be dried and made into wine to offer another opportunity for smaller local vintners to produce a product with a higher value than the products we have now.”

There is still a great deal of experimentation necessary to expand the valley sweet wine industry, such as which grapes are ideal, under what conditions should they be grown and how to treat those grapes after they have been dried. Fidelibus hopes to add ancient Greek winegrape varieties – such as Assyrtiko and Athiri –  to the collection of fruit he is growing for observation at Kearney.

“I think the Greek wines are very interesting,” Fidelibus said. “The way the grapes are dried is similar to the way raisins are dried here. Farmers are familiar with that kind of process. And the wines are very distinctive. “

Among the participants at the sweet wine seminar were Dinuba farmer Tory Torosian and his sons Tory Jr. and Sarkis. The Torosians cultivate a diversity of specialty fruit on an 80-acre farm at the foot of Smith Mountain. They sell their produce directly to consumers at San Francisco and Fresno farmers markets. Sarkis, currently a junior at Dinuba High School, is planning to major in enology at Fresno State or UC Davis and dreams of eventually producing a special sweet wine from grapes grown on the family farm.

“Those are the kind of people who would be able to do something like this,” Fidelibus said. “It wouldn’t make sense for them to make regular table wine. That’s readily available. These would be handmade, top quality wines that demand a premium price.”

Such a specialty product corresponds with the Old World custom of sharing an exquisite sweet wine with guests, a practice described by Wine Hall of Famer Darrell Corti at the sweet wine seminar.

“They are used as welcome drinks,” he said. “They indicate your standing in the household when they are served to you. The glass is always small, but it may be refilled often. They show the esteem the producer has for you. Table wine is for consumption. Sweet wines, especially the natural sweet ones, are for celebration. We should look at them in that light.”