April 06, 2005

SIUC prof studies new ways to preserve pork

by K.C. Jaehnig


Caption follows story

CARBONDALE, Ill. -- Open a package of pork that's been stored in your pantry for three months and if the smell doesn't kill you, the bad bugs will.

A researcher from Southern Illinois University Carbondale thinks it doesn't have to be that way.

"Our goal is to develop a pork product with a shelf life so greatly extended that it may not need refrigeration at all," says W. David Shoup, a professor of agricultural systems in SIUC's College of Agriculture.

"If we can do that, we can market it to other countries that don't have the electricity for refrigeration. We can improve the diet of our soldiers overseas. And one of the techniques we're using could protect the food supply from possible terrorist attacks. If crops were exposed to bacteria, instead of throwing them out, we could simply treat them."

In an old barracks building that serves as his lab, Shoup is experimenting with a mix of techniques for turning pork into a non-perishable food. The key to it all is ultraviolet light.

"UV sterilization can kill viruses, bacteria, molds and yeasts — all the things that cause food to spoil," Shoup says.

"We have designed a UV tunnel to treat pork, greatly reducing the bacteria count."

UV sterilization, sometimes called UV irradiation, is not new technology. It's already used commercially to disinfect drinking water and the shells of eggs. Canadian researchers have found it can kill E. coli bacteria in both apple juice and egg whites, while Belgian scientists have experimented with using it to treat fungi on newly harvested fruit and vegetables.

Still, most food irradiation at present is done with gamma rays or a powerful form of X-ray, both being high-energy wavelengths that can disable or kill both microbes and insects. (The FDA first approved such irradiation in 1963 as a way to get rid of insects in wheat and flour.) UV light with its longer wavelengths cranks out less energy, taking more time to achieve the same effect. That extra time became a real drawback.

"One of the reasons is because the UV tubes got quite hot so they were actually cooking the food, just like a microwave," Shoup said.

"Our design pulls the heat out — it never gets over 120 degrees — so we can leave the product in there longer without cooking it or affecting its taste and aroma."

Shoup is also using lasers to trim fat from the pork before he treats it.

"UV usually kills only on the surface," Shoup says.

"When you cut the meat with a saw like the butcher does, you get a rough cut. Those rough edges are great places for bacteria to hide. Using a laser leaves a smooth surface that gives you a very high percent of kill."

As a final step, Shoup vacuum packs his treated samples.

"What fat is left in the meat can't oxidize, which is the biggest reason pork goes bad," he says.

"We have collected preliminary data that suggest these three steps together can extend shelf life from the typical four days to a week to three or four months."

While continuing to collect data on how well the multi-step program works, Shoup is also recording microbial kill rates for varying amounts of UV exposure alone.

With that information in hand, he plans to send pork samples up to the Illinois Department of Agriculture's Centralia Animal Disease Laboratory, where they will be infected with 10 types of bacteria that cause food-borne illnesses, then treated in his UV tunnel.

"We'll get everything from salmonella and E. coli to listeria, which is far more wicked," said Shoup with a wicked smile of his own.
"We want to see how well we kill them."

Leading in research, scholarly and creative activities is among the goals of Southern at 150: Building Excellence Through Commitment, the blueprint for the development of the University by the time it celebrates its 150th anniversary in 2019.

(Caption: Wave of the future — An irradiation tunnel at Southern Illinois University Carbondale uses ultraviolet light to sterilize pork packages. SIUC researcher W. David Shoup is combining UV sterilization with laser-assisted meat trimming and vacuum packaging in an effort to create pork products that will not spoil even when unrefrigerated.)