The group, led by animal science and food science professor Joseph Sebranek, started with pork products in modified atmosphere packaging, which changes the composition of the air within the film-covered package. The researchers sought to determine if inhibitory improvement against pathogens might be achieved by packaging for pork loins and boneless ham muscles that were injected with potassium lactate and sodium diacetate.

Lactate and diacetate are already being used to reduce microbial growth. Scientists developed a hypothesis that a modified atmosphere of 99.5 percent carbon dioxide and 0.5 percent carbon monoxide would make the antimicrobials more effective.

Sebranek said the research showed that the high carbon dioxide levels did not appear to increase the effectiveness of the ingredients injected into the meats. A lower level of carbon dioxide – above 40 percent with the approximately 0.5 percent carbon monoxide level added to prevent discoloring – will help inhibit bacteria but appears to do so independently.

“There is still merit to the idea of using high carbon dioxide in modified

atmosphere packaging because there are concerns about those particular microbial inhibitors such as diacetate,” Sebranek said. “Some processors are beginning to back away from it because it has a bit of an acidic taste and a little sensory impact. The modified atmosphere would offer the opportunity to inhibit the organisms without the use of diacetate.”

“You would probably not want to go as high as 99 percent,” Sebranek said. “There can be a disadvantage to very high carbon dioxide, which is that meat systems will absorb a considerable amount if it’s in the atmosphere.”

Carbon dioxide by itself already been recognized for a significant effect of inhibiting pathogens, but concentrations over 30 percent or 40 percent usually result in discoloration of fresh meat. But in combination with carbon monoxide, the color is greatly improved.

“For fresh meat products, carbon monoxide gives you beautiful color,” Sebranek said. The low levels of carbon monoxide will maintain stable, cherry red color and allows greater levels of carbon dioxide for extending the shelf life.

With cooked, cured, processed products, the higher levels of carbon dioxide are acceptable. It doesn’t discolor those products as it does fresh meats such as ground meat or pork chops, where the use of carbon monoxide now offers significant color improvement.

Although combining modified atmosphere packaging with lactate and diacetate didn’t add any significant benefit, the use of modified atmosphere packaging on its own still provides industry an important option. “The big advantage is the use of carbon monoxide in fresh meat from the color standpoint,” Sebranek said. “That’s something that’s only recently been available.”

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