Can growers produce dried-on-the-vine (DOV) raisins that optimize both farmer returns and consumer tastes?

That’s the question two University of California researchers, Matthew Fidelibus, based at the Kearney Agricultural Center, Parlier, Calif., and Hildegard Heymann, a sensory scientist at UC Davis, are attempting to answer. They’ve released results of the third and latest in a series of experiments to determine how new production methods may affect raisins’ consumer appeal.

They chose Selma Pete and Fiesta varieties because of their contrasting characteristics. Both varieties are popular among growers who produce DOV grapes, but Selma Pete grapes ripen earlier, and are more acidic, than Fiesta grapes.

From previous research they knew that some consumers preferred raisins made from one grape variety or the other. But, they wanted to determine if grape maturity, as measured by a specific Brix degree, could also affect consumer preferences in raisins.

They hoped to identify an optimal maturity level for each variety — one that would produce an acceptable amount of raisins to meet quality standards for packers and also satisfy consumers in terms of sensory characteristics (flavor, appearance and mouth feel).

Raisins were considered acceptable to packers when at least 75 percent met the USDA’s “B & Better” airstream sorter grade requirements. A taste panel of consumers rated the sensory characteristics.

As it turned out, raisins that met packer needs could be made from Fiesta grapes with a 19 Brix reading and from Selma Pete grapes measuring 21 Brix.

“At those values, producers got good raisin yield and quality,” says Fidelibus. “We didn’t see a big increase in raisin yield or USDA grade if the grapes were allowed to ripen beyond that point. But, consumer acceptance of the raisins generally improved if the grapes were allowed to ripen further before drying.”

At present, he notes, consumers don’t know which variety of grapes raisins are made from or whether they are tray dried or DOV. But, the taste and consumer acceptance panels proved that raisins made from different grape varieties and from grapes of different levels of ripeness have different characteristics. Consumers can distinguish those differences. Highlighting the characteristics of different types of raisin might enhance consumer satisfaction and, thus, help expand markets.

“This and our previous studies have shown that type of grape and how you make the raisins affect consumer satisfaction,” he says. “This research could be continued with other varieties. Another step would be to collect demographic information about people who prefer one grape and raisin production method over another. Perhaps that information could be used to target the different varieties and types of raisin production practices to meet the desires of specific consumer groups.”