University of Illinois scientist helping processors keep E. coli out of meat

A University of Illinois food scientist has discovered that certain solutions used by meat processors to extend shelf life actually do double duty as antimicrobial agents, killing such virulent foodborne pathogens as E. coli 0157:H7.

That's important because E. coli can be spread via recycled solutions used to tenderize and enhance flavor in steaks, chops, and other cuts of meat, said U of I food science professor Susan Brewer.

The problem motivated Brewer and her graduate students to study the process used to inject meat with enhancement solutions before they're offered to consumers. And the results, published in the Journal of Food Science and Meat Science, have interested industry representatives.

"We wanted to find a point in the process at which we could exert some kind of control to keep foodborne pathogens from becoming a problem," said Brewer.

Brewer said that needle injection has been widely used for decades to tenderize meats, and more recently the fresh-meat industry has adopted the use of enhancement solutions, a practice that poultry and ham processors have used for years with very few problems.

"A certain amount of fat makes meat juicy and tasty, but in recent years consumers have been demanding leaner and leaner cuts of meat. Processors are now using the needles that tenderize steaks and chops to inject solutions that make the meat taste better and last longer," she said.

Picture a continuous end-line process in which needles inject cuts of meat with flavor boosters and shelf-life extenders. A basin catches fluid that goes through the meat or runs off the surface, and the solution is recycled into the system.

"With needle injection, organisms that exist on the outside of a piece of meat can get poked down into the meat where they're less likely to be killed if consumers like their meat on the rare side," said Brewer.

Also, as the needles inject one piece of meat after another, they can spread contamination from one piece of meat to another, and recycled enhancement solution can further complicate the spread of pathogens.

At this point, Brewer and her graduate students inserted themselves into the process to learn how contamination was likely to occur and how it could be controlled.

The scientists did two studies; in the first, they contaminated the surface of meat with E. coli K12, an indicator organism for its more dangerous relative, to observe the pathogen's progress as meat went through the system.

"We inoculated meat at various microbial loads, with some seriously nasty surface contamination on some pieces of meat," she said.

In the second study, they added E. coli K12 into the enhancement solution itself, experimenting with different components and combinations.

The scientists found that some solutions used to extend the shelf-life of meat also were effective at killing bacteria. "In certain solutions containing sodium lactate or sodium diacetate, bacteria cells couldn't grow and were substantially reduced. These shelf-life enhancers definitely work, and it really doesn't make any difference whether the steak itself or the solution is contaminated," Brewer said.

Brewer says the threat level for such meat cuts as chops, steaks, and roasts is not high, although ground meat not cooked to high temperatures can be dangerous. "You're always safe cooking red meat to 160 degrees, but if you have questions about food safety, check the USDA's Meat and Poultry Hotline at www.usda.gov," she said.

"The meat industry has been very proactive in attempting to prevent contamination of their products. They have an awful lot to lose if such an outbreak occurs," she said.

"But consumers should realize that the cook is the last point of control for eliminating these toxic organisms," she added.

"If meat is cooked until it's well done, you won't have a problem. These organisms are living cells, and they're fairly easily destroyed by heat, even E. coli 0157:H7," she said.

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Co-authors of the published papers were Brewer and graduate students C. L. Nicholalde, D. D. Paulson, M. C. Rojas, A. J. Stetzer, E. M. Tucker, R. A. Wicklund, and S. E. Wicklund.


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