There are foods you wouldn't necessarily want to add to. As Dr. Butler-Jones was mentioning about a risk-based system, you want to focus on those foods that have previously been involved in listeria outbreaks. For example, deli meats are obviously high-risk. You would want to add something like sodium diacetate to them to inhibit...but there are other foods that you cannot add to, because of their flavour characteristics. There are other foods, for example, that we know have never caused listeria outbreaks before.
On June 10th, 2010. See this statement in context.