Since this wouldn't have affected us, I didn't read this thread before. OK, I'm having a quiet moment!
I've got some info and some questions -
First, here is a link to more info on salmonella:
http://www.cdc.gov/salmonella/
They say that the incubation period is 12 to 72 hours. This fits with what I remember.
This recall (according to what I found) says it's for jars bought since May 2006. That should be still edible unless it's been kept with a loose lid in a warm environment.
Peanut butter DOES go off with time - it depends on how warm it is where it's kept, as well as other things. I've had an unopened jar go off, so it's not just exposure to contaminants. How it goes off - the oils in it go rancid. They taste bitter and are more solid in texture, like axle grease. I suspect, from a chemistry point of view (husband, correct me if I'm wrong, this is your field) that this involves chemical changes in the long chain of carbon atoms that makes up the oils. Any doubly bonds are saturating, possibly combining with oxygen or other groups from within the peanut butter and when this happens in organic chemistry it can totally change what sort of chemical it is, from an acid to an alcohol to an oil to... anyway, the consistency gets stiffer, the product tastes awful and you feel nauseated (maybe just from the taste). I've never got sick from tasting (and throwing out) rancid peanut butter, but it's put me off it for a long time.
ANY peanut butter will go off. For years we used to buy natural peanut butter, ground fresh while you wait. Nothing in it but peanuts. It would begin to goo off in a matter of weeks sometimes. Then I began making it myself, in the blender. Then the kids began to demand peanut butter in bulk so I searched the shelves for some good stuff with no additives. Then they stopped eating it - hence my discovery of what rancid peanut butter tastes like (by the way, the chemical changes begin long before it's unpalatable - you can taste the early changes and it's a sign to either use it up fast, or give up and throw it out now).
One point - if the nuts are old, the freshly made peanut butter will also taste 'old'. You get the best results with fresh nuts. The oils will degrade in the nut, too.
I was thinking that if you cook with the peanut butter, melting it out completely and raising the temperature high enough to kill the salmonella, it should be fine. There are some biscuit recipes, for example. Or satay sauce. You would need to heat the peanut butter thoroughly first before you add it to the recipe. I think somewhere I've got a recipe for roast chicken that's been smeared with peanut butter. husband would divorce me if I cooked it for him. But I just checked the FDA's website - they do not recommend you cook with it. I suspect that is because it's difficult to be sure you have heated it hot enough or for long enough. SO - it's probably best to just chuck it out, because it's not expensive stuff and it's a lot cheaper to buy a new jar than to end up with 7 days of diarrhoea.
And for those who are now wary of peanut butter - try making your own cashew butter. It's different, very tasty, great for kids (who don't have a nut allergy).
One last question - is this a recall where you get refunded, or is it just a warning to throw it out? I couldn't find any reference to "return it to your nearest retailer for a refund".
Marg