Mixed greens and bagged salad mixes (regardless of how many times they are washed prior to purchase) have a tendency to carry certain bacteria associated with poor sanitation because they are handled so frequently. Mixed greens also get a dark, slimy appearance as they expire; a visual cue that they’re no long safe to consume.
Fresh berries can carry a parasite called cyclospora. Always wash berries thoroughly before consuming them and don’t use them past their expiration date or once they begin to break down, whichever comes first.
Deli meat should never be consumed past its expiration date, even if it hasn’t developed a strange odor or slimy appearance; it can carry listeria, bacteria that can grow in cold temperatures. That means listeria can thrive even if your deli meat has been properly stored in the refrigerator.
The chances of an egg being contaminated inside the shell are very low (about five thousandths of one percent) but egg shells commonly carry bacteria. If your eggs have passed their expiration date it’s best to either toss them or use them for hard-boiled eggs.
Ground meats are generally more dangerous to consume post-expiration date when compared with whole cuts of meat; ground meats are handled more (including the grinding process) and may include meat from many different slaughterhouses – all this adds up to more opportunities for contamination.
Soft cheeses (especially those made with unpasteurized milk) can be contaminated with listeria. With soft cheeses it’s difficult to effectively trim away any moldy or spoiled portions. If soft cheeses like queso fresco, feta, brie, or blue are past their expiration date it’s best to throw them away.
Alfalfa sprouts can be dangerous to consume after their expiration date as well. The sprouts need a warm, moist environment to grow, the same environment bacteria needs to thrive. Since spouts are most often eaten raw, it’s difficult to eliminate any bacteria that may be present.
Consumer Reports tested 300 store-bought chicken breasts for bacteria; 97% of the chicken breasts were contaminated — not surprising given the conditions under which chickens are raised, and rising nationwide concerns about antibiotic-resistant bacteria. If your chicken is past its expiration date, toss it — it’s not worth the risk.