Eggs

Eggs keep 3–5 weeks refrigerated from the day you bring them home, which is usually well past the date printed on the carton.

Keep them in the carton, on a shelf, not in the door. This is the single most common egg storage mistake. The door is the warmest part of the refrigerator and swings through room-temperature air every time you open it, and eggs are unusually sensitive to temperature cycling. The carton also matters: it limits moisture loss and stops eggs absorbing odors through their porous shells.

Store them pointed end down. The air cell sits at the blunt end, and keeping it uppermost helps the yolk stay centered and away from the shell.

Do not freeze eggs in the shell — they expand and crack. You can freeze eggs out of the shell: beaten whole eggs keep about a year, and whites freeze perfectly. Yolks need a pinch of salt or sugar beaten in first, or they turn gluey.

Refrigerate eggs promptly after shopping and do not wash them.

American eggs have to be refrigerated for a reason that surprises most people: they have been washed.

A hen coats each egg as she lays it with a natural antimicrobial layer called the cuticle or bloom, which seals the shell's thousands of pores. US regulations require commercial eggs to be washed and sanitized, which removes that cuticle along with any contamination. The egg is cleaner but no longer sealed, so it must stay refrigerated from packing plant to kitchen. In much of Europe eggs are not washed, keep their cuticle, and sit unrefrigerated in shops — the same food, a different strategy. Once an egg has been refrigerated it must stay refrigerated, since warming causes condensation that draws bacteria in through the pores.

The pathogen of concern is Salmonella Enteritidis, which is unusual in that it can be present inside an intact, perfectly clean egg — passed from the hen before the shell formed. This is why egg safety is about cooking and cold storage rather than shell inspection, and why runny yolks carry a small residual risk for vulnerable people.

Aging itself is mostly a quality matter. Moisture and carbon dioxide escape through the pores, the air cell grows, the white thins, and the yolk membrane weakens — which is why old eggs spread flat in a pan and fresh ones sit up.

The float test is widely misunderstood. A floating egg is old, because its air cell has grown. That is all it tells you — it is a measure of age, not of safety. Judge by cracking the egg into a separate bowl and checking for an off smell or unusual color.

The date on an egg carton is not a safety deadline. "Sell by" is a stock-rotation instruction for the store, and federal rules require it to be no more than 30 days after packing. "Best by" or "use by" is a quality estimate.

Properly refrigerated eggs are generally good for 3–5 weeks after you bring them home, which often runs past the printed date. USDA-graded cartons also carry a three-digit Julian date — the day of the year the eggs were packed, from 001 to 365 — which tells you the real age far better than the sell-by date does.