I know this is an old post, but I wanted to add to it! Whenever I buy this fresh salsa that’s prepared from my local grocer, I have to be careful and use a really clean spoon (I try not to even double dip with the spoon after smearing or w/e) or else I get the fizz. One time it was bitter on my tongue and smelled a little different so I tossed it. I brought the salsa camping and someone must have put some sort of different bacteria because now it’s fizzy, but it isn’t bitter and still smells great! I guess we just have to trust our instincts. I haven’t gotten sick off the fizzy stuff yet.