A 2010 study from Consumer Reports found that nearly 40 percent of pre-washed salads sold in plastic bags or so-called plastic clamshells may be contaminated with bacteria that could be harmful to your health.
They did a small study, just over 200 samples, and they found that 39 percent of those samples contained a family of bacteria known as coliform, which is a general indicator for contamination. Twenty-three percent of them contained a bacteria known as enterococcus, which is usually associated with fecal contamination. Not what you want to hear in your produce. It's not sterilized, it's just pre-washed.
But there weren't other bacteria found in the study that we tend to associate with foodstuffs. It's important to note they did not find E.coli, they did not find salmonella, but they actually found the worst contamination in package containing spinach. We've heard a lot about spinach in the past. Spinach was a big offender and especially those packages that were bought within one to five days of their recommended sold by date.
It is important to remember is that bacteria usually doesn't like cold temperatures. So when you take it home from the store, keep it refrigerated and rinse it, don't soak it in water - let water rinse through it. It's helpful in removing some of the soil contamination.
1. Buy a bag that is within it's Sell By date and refrigerate immediately.
2. Before using, rinse the greens under running water.
3. Keep any unused greens in the fridge.