We’ve heard the complaints, and have even made them ourselves: You buy a bag of prewashed lettuce, paying a premium because it’s convenient and attractive, open it on or before its use-by date, and find brown or gooey leaves among the green. Is it your imagination, or is this stuff old before its time? What’s more, the bag might say “ready to eat,” but are unwashed greens safe?

With $2.5 billion of precut salads sold in supermarkets in one year, the concerns can become serious for a lot of consumers. In late July, there was a voluntary recall of some packages of Classic Salads lettuce and spinach that could have been contaminated with salmonella. (The potential problem was found during routine sampling by the company, and no illnesses had been reported as of press time.) And in 2005, about 250,000 packages of Dole salad were voluntarily recalled because of possible contamination with E. coli bacteria. Without admitting fault, Dole recently settled four lawsuits and an undisclosed number of claims from consumers who complained of stomach cramps, bloody diarrhea, or, in one case, acute kidney failure after eating the salads.

How we tested. We chose six bagged salad blends from two of the biggest purveyors: Dole’s American, Classic Iceberg, and Spring Mix; and Fresh Express’s Double Carrots, Green & Crisp, and Spring Mix. Then we performed two types of tests. For our yuck test, we bought 32 bags of those salads, opened them on or before their use-by date, sniffed, and went through them leaf by leaf, weighing the pieces deemed inedible or undesirable. For our bacterial test, we sent 62 bags to a lab to have them analyzed for generic E. coli, which can indicate contact with fecal material but isn’t necessarily hazardous to your health (E. coli O157:H7 is the best-known hazardous strain).

What we found. Only one of 62 bags harbored a detectable level of generic E. coli, but results of our search for brown, gooey leaves might make you say “yuck” a little too often. The percentage of inedible salad per bag, by weight, ranged from 0.5 percent to 83 percent. Sometimes even salads with a low percentage of inedible leaves looked so unappealing overall that we would have thrown out the whole bag. What’s more, the vast majority of bags had “off” odors, smelling like rotten vegetables, sauerkraut, or chlorine. A couple of salads smelled like imitation crab meat.

Asked to comment about use-by dates, Dole said that it stood by them. “I think it’s pretty amazing the shelf life you do get from the lettuce,” said Marty Ordman, Dole’s vice president of marketing and communications. “You’re talking about a fairly sensitive vegetable product.” Fresh Express said that its dates are valid if the salads are properly handled and refrigerated.

CR’s take. If the convenience of precut lettuce encourages you to eat your greens, great. But bagged salads can be less fresh than homemade, might have “off” odors and wilted lettuce, and usually cost more. Per pound, we paid from $1.73 (for an iceberg blend) to $11.17 (for a spring mix). Our homemade equivalent of the iceberg blend cost about $1.35 in ingredients.

Further­more, produce is more open to bacteria when it’s cut up than when intact. Always wash salad, even if it’s labeled as prewashed. Other sensible advice, from Fresh Express: Refrigerate a bag of lettuce as soon as you get it home, keep unused lettuce in the original packaging, and seal the bag tightly.

Finally, be sure to check for the latest safety alerts regarding fresh produce. In September 2006, an outbreak of E. coli led to the recall of several brands of bagged spinach--and advice from government agencies to avoid all fresh spinach. You can find CR's coverage of the E. coli outbreak here, and the latest information on this and other food-safety issues on our safety blog, Consumer Reports on Safety.