This is from the March 2010 issue of Consumer Reports and is available free online.
They are convenient and a good buy when you don't eat enough greens to justify whole heads of lettuce or bunches of spinach but they do have a risk. None of these greens found contaminated would have made you sick but it does show that they are not properly cleaned and protected from environmental contamination. The article goes on to recommend how you can reduce your risk when using these packaged greens.
- Buy packages far from their use-by date.
- Wash the greens even if the packages say "prewashed" or "triplewashed." Rinsing won't remove all bacteria but may remove residual soil.
- Prevent cross contamination of greens by keeping them away from raw meat and poultry.