Edited 5/16 9:21 pm to reflect additional information (at end of post)
If you go to a grocery store in the Pacific Northwest, you can find packaged, sliced, deli meats advertised as being free of preservatives. Natural foods advocates love it–no preservatives, yay!–but I wince. See, I study a bacterium which thrives in deli meats–Listeria monocytogenes. This little rascal is unfazed by salt, refrigeration, and semi-acidic foods. In many other foods, Listeria monocytogenes would be killed by cooking, but we don’t generally cook deli meat, so any bacteria in it at the time of packaging will be live and healthy and maybe multiplied when you go to eat it. It is, however, slowed down by preservatives. So when I see preservative-free, all I see is an opportunity to possibly acquire listeriosis.
Now, for the good news. Listeria monocytogenes is rare in packaged deli meats (if you want to really risk some listeriosis, buy deli meats from the deli counter). Nonetheless, I prefer to reduce my risk by buying deli meats with preservatives. Maybe it’s a microbiologist thing, but I’m more worried about the bacteria than the chemicals.
Caveat and addendum–A friend of mine sent me an article which explains how companies are able to claim their product has “no preservatives” while still maintaining “cured” properties in their product as well as some bacterial growth inhibition. Basically, the company mixes celery juice or other vegetable products in, along with some safe bacteria which can convert the chemicals naturally found in the celery juice into the normal form of the preservative. The actual chemical content of the preservative is lower in these “preservative-free” meats, but they still contain preservatives which are identical to those in normally labeled preserved meats. So it’s mostly a marketing gimmick, which comes with slightly reduced food safety, but not as much as I’d originally thought.