UW-Stout News Story

Professor’s study offers promise of fresher, safer asparagus

January 5, 2012

For many people, eating a nutritious stalk of asparagus is a rite of spring. The tender green vegetable is one of the first kinds of local produce to appear in grocery stores each year.

Unfortunately, asparagus growing season is short. Also, because commercially sold asparagus undergoes very little processing and has a high respiration rate — the speed at which it breaks down — it usually lasts less than a week on store shelves.

What’s more, fresh-cut asparagus is susceptible to bacteria because it rapidly loses moisture.

Recently published research led by Joongmin Shin, a University of Wisconsin-Stout assistant professor in the engineering and technology department, could help alleviate those problems.

Shin and three colleagues from Michigan State University found that asparagus exposed to low doses of x-ray irradiation had less bacteria and maintained sugar levels, thereby slowing the respiration rate and extending shelf life, possibly up to 75 percent.

“This is an effective way to control the respiration rate,” Shin said. “X-ray treatment will enhance consumer safety by decreasing the number of viable micro-organisms on asparagus.”

The asparagus treated with x-rays was in a typical consumer package, a vacuum-packed tray covered by breathable plastic film.

Further tests must be done, such as for taste, before the results of the study could be implemented by distributors, Shin said.

Another hurdle, Shin said, is a lack of widespread public acceptance of irradiation. X-ray irradiation is the newest irradiation technology commercially used for foods; other types are gamma ray and electron beam irradiation.

Irradiation is approved by the Food and Drug Administration, and the Center for Disease Control calls it “safe and effective.” No radioactive substances are used. Some consumers and consumer groups, however, have concerns about the safety of irradiated food.

Testing for the study was conducted at Michigan State in East Lansing, Mich. Shin’s co-researchers were MSU professors Bruce Harte, Janice Harte and Kirk Dolan. The study was published in HortScience, a journal for the American Society for Horticultural Science.

Michigan is one of the leading producers of asparagus. Imported asparagus, because of distribution time, would benefit the most from extended shelf life. Asparagus from Peru was used in the study; it had bacteria many times higher than U.S. asparagus but still was safe to eat.

Shin, in his second year at UW-Stout, earned his Ph.D. at Michigan State and previously was involved in a postdoctoral asparagus study there. He teaches courses in UW-Stout’s packaging program, including a class on food packaging.


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