Largely due to frequent recalls, lettuce (romaine in particular) has gained a reputation as a generally untrustworthy vegetable. And many people, operating under the “better safe than tormented by foodborne illness” mentality, are quick to trash any lettuce with even the slightest imperfection.
One especially common defect is the tinges of pink you’ve probably seen throughout lettuce that’s spent several days in the fridge. As Eat or Toss? reports, this is often the result of a stress response called “pink rib,” which can happen when lettuce is stored at the wrong temperature, starts to get old, or experiences other less-than-ideal conditions. But while pink may seem suspicious on a green vegetable, it’s not a red flag on its own.
Catherine Belisle, a Ph.D. student in horticulture at the University of Florida, studied the progression of pink rib in some lettuce over four weeks. “I didn’t see any symptoms of decay from microorganisms or from fungi,” she told Eat or Toss?. And while she acknowledges that pinkish lettuce could taste a little bitter, she’s personally always thought it tasted the same as unstressed lettuce.
In other words, if your lettuce has a few pink bits but is otherwise dry and crisp, it should be fine to eat. If, however, it’s exhibiting classic signs of decay—it’s wet, slimy, soft, malodorous, etc.—you should toss it. If the discoloration on your lettuce is more brown than pink, it could be the result of oxidation (the same reason apple and avocado slices turn brown) or exposure to ethylene, a gas released by certain fruits and vegetables that can cause other produce to ripen faster. According to Livestrong, brownish spots on lettuce aren’t a health risk by themselves, either; but, again, if they’re accompanied by other issues like sliminess or foul odor, you shouldn’t risk it.
[h/t Eat or Toss?]