Lobster

The governing rule for lobster is simple: cook a live lobster the day you buy it. After cooking, the meat keeps 3–4 days refrigerated.

Keep a live lobster in the refrigerator in a container covered with a damp cloth or damp newspaper — never sealed in a plastic bag, and never submerged in fresh water. Both suffocate or kill it, and a lobster that dies uncooked is a problem rather than an inconvenience.

Cook lobster tails and meat, once removed from the shell, within 3–4 days. Cooked lobster freezes for 2–3 months and does much better frozen in the shell or in its own cooking liquid, which shields the meat from air.

Frozen raw tails should be thawed in the refrigerator overnight and cooked immediately.

Lobster is the clearest illustration of why some shellfish are sold alive, and the reason is enzymatic rather than bacterial.

Lobster tissue contains powerful digestive enzymes, and on death these begin breaking down the surrounding muscle almost at once — a self-digestion that proceeds rapidly even under refrigeration. Within hours the meat turns soft and mushy and develops off flavors. This is why lobsters are kept in tanks rather than on ice, and why a lobster that dies before cooking should be discarded rather than cooked. It is not a question of squeamishness; the meat genuinely deteriorates that fast.

Live lobsters also carry Vibrio and other marine bacteria in their gut, which spread through the meat once the animal's own defenses stop working. Cooking a lobster that died an unknown number of hours ago means cooking an unknown quantity of bacterial growth and enzymatic damage.

Once cooked, lobster behaves like other cooked seafood: 3–4 days refrigerated, watching for sour smell and slimy texture.

The green tomalley (the digestive gland) and red roe are normal and edible, though the tomalley concentrates contaminants and health advisories recommend limiting it.