ALBANY, Ga. (AP) -- The timing of the harvest can determine whether peanut butter is a "roasted peanutty" treat for the taste buds, or a pain in the palate with flavors that can range from paint to cardboard, according to a new research study.

Scientists have known for years that harvest timing can affect peanut yields, quality and taste.

The taste aspect was highlighted again when a team of researchers launched a three-year study to determine the optimal maturity dates for five new peanut varieties. They compared the taste and performance of those varieties with a well-established variety, the Georgia Green, which accounts for about 60 percent of the peanuts grown in the Southeast. "Harvesting at optimal maturity is extremely important as far as flavor is concerned," John Beasley, a University of Georgia peanut agronomist and member of the research team. "We know from previous research and from the industry that when immature peanut kernels are processed, they develop a bitter or off-flavor taste."

One part of the study compared the taste of peanuts that were harvested at full maturity with peanuts that were harvested 10 days early and 10 days late. They peanuts were submitted to a U.S. Agriculture Department Laboratory in North Carolina and to a private laboratory in Albany for evaluation by taste panels.

Years of training and practice have equipped these gustation experts to detect the 32 taste descriptors of peanuts, including sweet, bitter, sour, paint, woody and cardboard. The optimum taste is roasted peanutty.

With U.S. growers facing stiffer competition from Argentina, China and India — countries that may offer lower prices on the world market — there's pressure on them to offer the highest quality.

Georgia produces nearly half the nation's domestic peanut supply, mostly for peanut butter. "Georgia has maintained a reputation for having the best, most consistent-tasting peanuts around because our growers get the crop in when it needs to come in," Beasley said. "We need to continue doing this because the peanut industry is competitive and consumers will taste the difference."

Anna Resurreccion, a food scientist at the university's research center in Griffin, said harvest timing has a huge impact on the flavor profile of peanuts.

"It's that roasted peanutty flavor that's most important," said Resurreccion, who has been conducting peanut taste tests for 21 years, but was not involved in Beasley's project. "Harvesting at an immature state introduces off flavors," she said. "These do not bring out that roasted peanutty flavor. When the peanut butter tastes like cardboard instead of freshly roasted peanuts, you know something is wrong."

Peanuts mature 135 to 160 days after planting, depending on the variety, but growers can't rely strictly on a time factor because of varying climatic and environmental conditions.