Dunno. Not my area of expertise. I'm just repeating what I heard on The Today Show from their medical reporter.
I *do* know that whenever I'm in a hurry and buy a bag salad, I open it up in the checkout line. If it smells sour, I refuse to pay for it. I can't tell you how many times in the past I have gotten dinner ready, thrown a bag salad into a bowl to mix it with dressing, and smelled that awful smell. Then we either have to drive to the store when the rest of the dinner is ready or skip the salad. As a result, now I very rarely buy bag salads. The exception is the Dole salads that are in a box instead of a bag. They very rarely have that funky smell. My theory is that the greens don't get bruised in a box like they do in a bag, so they last longer. Plus there are ventilation holes in the boxes but not in the bags. This theory of mine was reinforced tonight when I heard a CDC official on the news say that one problem with bag salads is that the bag is totally sealed, so if there is the tiniest bit of bacteria, the sealed bag is a perfect environment for their rapid growth.
