Most Vidalia onion lovers choose the Georgia-grown onion because it tastes sweet. University of Georgia scientists are searching for a way to help Vidalia onion farmers guarantee their crop meets consumers' expectations - sweet, but not too pungent.

"Basically we are trying to get a good measure of pungency," said Rob Shewfelt, a food scientist with the UGA College of Agricultural and Environmental Sciences and leader of the project. "You're not going to find a Vidalia onion that is as pungent as a green onion or a red onion, but certain ones are pungent."

Shewfelt calls pungency "a relative term."

"When you chew an onion with your mouth closed, you taste the sweetness, then you open your mouth and get the pungency," he said. "Pungency is what goes up the back of your nose and makes your nose vibrate, whether it makes you cry or makes it feel hot in your mouth."

UGA scientists are in the final year of the four-year study comparing instruments that measure sweetness and pungency with the views of human trained sensory panelists and untrained onion tasters.

"Years ago, (UGA researcher) Bill Randall used an instrumental method where fresh onions were crushed and measured," Shewfelt said. "Basically, it measured pyruvic acid and the enzymes and substrates that combine and cause us to tear up."