WOOSTER, Ohio - Something as simple as moisture levels or heat stress can alter the chemical characteristics of a vegetable crop, which may change its nutritional or market value.
Ohio State University vegetable researchers are studying how farm management practices are tied to the biochemistry of a crop and whether specific techniques can be applied to alter chemical compounds in the plant that tie together its health and market value.
"We know that management matters in crop production. There's enough scientific evidence to support our looking at these effects on crop quality," said Matt Kleinhenz, an Ohio State Extension vegetable specialist with the Ohio Agricultural Research and Development Center. "What we need to know more about is what the crop goes through when it's irrigated or is stressed through heat or lack of water. We want to nail down definitively what a grower needs to do to specifically optimize the level of those compounds that are related to the potential health or market value of the crop." One vegetable crop the researchers are focusing on is cabbage, which contains compounds known as glucosinolates. The compounds, also found in broccoli, Brussels sprouts and horseradish, have been associated with preventing cancer.
Additionally, they have ties to flavor. The vegetable, when chewed, combines with an enzyme in the plant tissue that releases the glucose, or sugar portion of the compound. This action leaves behind a component that produces the perceived bitter or spicy taste associated with those vegetables.
"It's thought that heat stress can affect the levels of those compounds. Higher temperature or heat stress would increase the levels," said Ted Radovich, an Ohio State doctoral student who is working on the project. "If we can characterize the relationship between the environment and plant response, we may be able to manage those stresses in the field and manipulate those chemical levels." Another crop researchers are studying is red lettuce. The lettuce contains anthocyanins, natural colorants that give red lettuce its red color. Anthocyanins also exhibit antioxidant properties, which, among other things, guard against cancer, cardiovascular and neurological diseases and diabetes.
"Red lettuce is visually appealing. Consumers tend to be more attracted to lettuce that has the most red color," said Kleinhenz. "So if we can identify the environmental factors - water, light, temperature, soil moisture - that can affect pigmentation, we can offer a product that is important in the marketplace from a crop's appearance and has a nutritional value." Aparna Gazula, a master's student, is studying these issues in field and greenhouse-grown lettuce.
The studies not only involve fieldwork, but sensory evaluations, as well, to determine the relationship between chemical levels and consumer preference.
"Because human perception of flavor is so complex, there are many different relationships between consumption and chemical levels that must be identified," said Radovich.
For example, over 100 different glucosinolate compounds that have been identified and many can produce a different response in taste and odor, he said.
"If we can find a crop with high glucosinolates or anthocyanins that produces an odor and taste consumers like, then we can potentially go back in the field and adjust practices to produce that desired product," said Radovich. "The evaluations are a way of standardizing the measurement of crop sensory quality." The study is supported through the OARDC Seed Grant program.