Debbie Payton has never liked onions. She didn’t eat them growing up, and she won’t eat them now.

Which is unfortunate, since it’s her job to find out just how pungent onions are.

The smell is predictably powerful inside AgSource Laboratories in Umatilla, where Payton diligently peels, cores, mixes and mashes onion samples from across the country for testing. Farmers request pungency tests around harvest time as a marketing tool for their produce.

The process is long and labor-intensive, said Payton, one of four lab technicians at AgSource. And, while the staff also tests for things like nitrates in wastewater and manure, Payton says onion pungency is her least favorite responsibility.

“Sometimes I’ll smell it all day,” she said. “If they get really bad, I’ll turn the exhaust fan on.”

Onion pungency is measured by the amount of pyruvic acid contained in the bulbs — that’s the chemical that makes people’s eyes sting and water. Sweet onions typically have higher amounts of sugar and low pungency, which is why they’re so popular and able to fetch a higher price in stores.

It might seem like all Payton has to do to gauge pungency is take a whiff and fight back the tears, but there’s a lot more to it than that, she said. Her work area is like a cross between a kitchen prep station and science lab, with cutting board and knife alongside chemicals and test tubes.

Preparation is the key to good data, Payton said as she puts on a pair of blue rubber gloves. Each sample contains a batch of 5-10 onions, which are peeled and cored into a large bowl. After mixing, samples are measured out and pureed into an onion slurry, with the liquid filtered into separate tubes.

Hydrochloric acid is added to the mix, which turns the solution a different color that ranges from light orange to brown. The color is then measured as a wavelength of light using a small electronic device known as a spectrophotometer.

Payton takes those values and runs one final calculation to come up with a number somewhere between 0-8. The lower the number, the less pungent the onion. The less pungent the onion, the more money a grower can potentially make off the crop.

“They get pretty ecstatic when it’s between a 1 and 4,” Payton said.

A different test, known as a Brix test, measures the sugar content of onions and can be done in seconds, as opposed to hours. Payton places a small amount of onion juice on a Brix reader, which resembles a long kaleidescope, to come up with the reading.

Occasionally farmers disagree with the results of the test. That doesn’t come as a surprise to Craig Simson, business agronomy manager at AgSource, who has seen how competitive onion growers can be.

“We had one fairly large client stay here all day and watch us from beginning to end,” Simson said. “This pungency is a very personal thing to an onion grower.”

AgSource is a large farmer-owned cooperative with seven labs nationwide, primarily in the Midwest. Umatilla is the co-op’s western-most location, and the only lab that does onion pungency testing. Most samples come from around the Columbia and Walla Walla basins, Simson said, but sometimes are sent in from out of the region.

The test is used mostly for marketing, but can also be used in a variety of ways, Simson said.

“By testing at the end of the year, they can compare their secrets and growing techniques to the final result,” he said. “What people are looking for is high sugar and low pyruvic acid ... People don’t want something that makes you cry and burn.”


Contact George Plaven at or 541-966-0825.

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