Health Canada gave the go-ahead on September 20 for food processors in Canada to use sodium diacetate as a preservative in meat, poultry and fish products. When used in combination with sodium lactate, the preservative can curb the growth of Listeria monocytogenes.

Spokesperson Linda Smith said Maple Leaf is aware of the approval and is "assessing it."

The food producer shut down a meat processing plant in Toronto on August 20 after Listeria contamination was detected and linked to the nationwide listeriosis outbreak. The plant underwent an intensive sanitization and production resumed on September 17. Initial product runs were still being tested when, on October 8, more Listeria was detected.

Chief executive Michael McCain held a news conference to stress the prevalence of Listeria. It is everywhere, he said, and reasonable to assume most people consume it every day.

It is however dangerous in very high levels, and food scientists say should low levels of Listeria exist on equipment in plants the preservatives could ensure it never multiplies to dangerously high levels.

Food scientist Martin Wiedmann said sodium diacetate can completely prevent the growth of Listeria or slow it down, depending on several factors. However, he cautioned against viewing it as a "magic bullet" solution.

"It's one piece of an effective total strategy to reduce the risk of Listeria contamination," he said.

From the October 27, 2008, Prepared Foods e-Flash