Stressing a carrot
It happens all the time at work: you have more tasks to do, you're stressed and challenged, but you're more productive today than last year. Why not applying this principle to fruits and vegetables? This is what has done Luis Cisneros-Zevallos, Assistant Professor at the Department of Horticultural Sciences of Texas A&M University. Cisneros and his team found they could easily stress carrots to produce five more times "phenolic compounds" which are associated with a reduced risk of cancer and heart disease. This could be beneficial to the $76 billion U.S. food industry as well as individual growers. Cisneros is also working on other kinds of fruits and vegetables, such as potatoes. But read more...
Here are some comments from Luis Cisneros-Zevallos.
"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."
On the left is an illustration of Cisneros's proposed concept for using controlled postharvest abiotic stresses to enhance the nutraceutical content and adding value to fresh fruits and vegetables (Credit: Luis Cisneros and his research group). This diagram was extracted from a document that Luis Cisneros sent me, "The Use of Controlled Postharvest Abiotic Stresses as a Tool for Enhancing the Nutraceutical Content and Adding-Value of Fresh Fruits and Vegetables." This article has been published by the Journal of Food Science under a slightly different title in 2003.
Now, let's look at a real example of what these techniques could bring -- without genetically modifying the plants.
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 "fresh produce" and they accumulate more anthocyanin, that means more money," he said. "Now imagine using that " fruit or vegetable" 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."
Both food processors and growers would make more money by increasing the percentage of phytochemicals produced by various fruits and vegetables. Still, the researchers admit that they still have to check if they can replicate the success they had with carrots.
Cisneros latest research work has been published by Food Chemistry under the name "The increase in antioxidant capacity after wounding depends on the type of fruit or vegetable tissue" (Volume 101, Issue 3, 2007, Pages 1254-1262). Here are some numbers picked from the abstract.
Phenolic changes ranged from a 26% decrease to an increase up to 191%, while antioxidant capacity changes ranged from a 51% decrease to an increase up to 442%. Reduced ascorbic acid decreased up to 82%, whereas the changes in anthocyanins and carotenoids were less evident. In general, the wound response was dependent on the type of tissue and influenced by the initial levels of reduced ascorbic acid and phenolic compounds.
Even with these encouraging results, the researchers know that there more research is in front of them. "We are trying to see if these responses can be duplicated in other types of plants -- different types of fruits and vegetables," said Cisneros.
Sources: Kathleen Phillips, Agricultural News, Texas A&M University, October 6, 2006; Luis Cisneros-Zevallos documents; and various websites
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