Protecting ready-to-eat beef from pathogens

Vacuum packaging meat products has made it possible to keep them fresh in appearance and taste. The problem is that pathogenic bacteria can grow on the meat in this packaging at both room and refrigeration temperatures.

Food Safety Consortium researchers at Kansas State University have found that a solution of sodium citrate can inhibit the growth of the bacterium Clostridium perfringens on restructured roast beef.

Ready-to-eat meals go through a mild heat treatment, but the treatment stimulates rather than reduces the growth of the bacterium in vacuum packaging. One way to prevent the problem would be to follow federal guidelines to sharply cool down the meat within five hours. But not all of the current refrigeration technology makes that possible.

So, according to KSU food science professor Daniel Fung, "There is a need for additional secondary safety barriers in vacuum-packaged meat products that will help prevent the growth of anaerobic bacteria such as C.perfringens during cooling procedures."

C.perfringens is a common foodborne bacterium that is claimed to be responsible for more than 6% of bacterial foodborne disease.

Fung's experiments showed that all sodium citrate treatments reduced C.perfringens after the cooking step and before the end of the 18 h cooling step and suppressed its further growth.

The process would be particularly beneficial to smaller meat processors that may not have the equipment to cool down their meat far enough fast enough. Fung said sodium citrate would create another hurdle to block the growth of C.perfringens.

With ground beef, results were similar after heating followed by cooling. "The combination of heat and sodium citrate proved to an effective preventive method against C.perfringens growth by damaging the bacterium's cell structure," Fung said.

Fung said his research team continues to examine the issue by using electron microscope transmissions to study the mechanism of killing the pathogen. "We want to see whether the organisms disintegrate or whether the cell structure changes," he said, noting that industry could likely use such data.