Vegetables, Like People, Urged To Live Up To Potential

A major stress in a carrot's life – like the slash of a kitchen knife – and the tapered tuber kicks in the juice and pumps up its phytochemicals.

That's the finding of Dr. Luis Cisneros, Texas Agricultural Experiment Station food scientist. He calls it abiotic stress – pushing the button, so to speak, on a crop after it has been harvested.

"What happens is that on many occasions, plants do not express their real potential. They can actually express more if they are challenged to a point," he said.

"It's something similar to what would happen with people. You stress people, and people tend to respond more to the challenges in front of them," he added. "In this case, when you stress plants, you actually trigger this genetic response, and the plant will synthesize chemical compounds. You end up with a carrot that is healthier than the original carrot in a short period of time with a very cheap and easy stressor."

A key to his research was understanding the plant's pathway to a specific, desired compound and getting it to increase only that one. So far, his lab has successfully increased the amount of antioxidant activity in carrots up to five times.

The finding is important for food processors, Cisneros said, because as companies increasingly seek ways to add healthier components to foods, the technique could yield more of those desired substances.

One kilogram of anthocyanin extract is valued at $1,000 in the marketplace, Cisneros said. Anthocyanin is the red pigment in vegetables which is associated with a reduced risk of cancer and heart disease.

"So, if you stress (carrots) and they accumulate more anthocyanin, that means more money," he said. "Now imagine using that carrot to make a juice or making an extract of it that could be added to bread or some other product. You end up with an array of different products that you can benefit from."

Growers also stand to gain, he said. In traditional vegetable marketing, the only way for a producer to make more money is to harvest higher yields.

"But with this process, a grower could market not for the yield in tonnage, but for the percent of phytochemicals," he explained.

Other current research on producing phytochemicals in foods focuses on breeding fruits and vegetables to have increased amounts of the compounds, Cisneros noted. While that is beneficial, the ability to quadruple the phytochemical with a simple, post-harvest technique would add even more value.

In his lab, the "wounded," or cut, carrots were placed under an ultraviolet light for a few seconds. Analysis a couple of days after that simple treatment showed a "huge increase" in antioxidants, he said.

"Abiotic stress has been known for decades," he said. "But our work is new because we targeted something specific to accumulate what we wanted. We used stress to manipulate."

The finding opens the door for more research, he said.

"We are trying to see if these responses can be duplicated in other types of plants – different types of fruits and vegetables," he said. "We want to see the signal molecule that is promoting these types of responses to maybe improve the way we are applying these stresses."