Egg Substitute

Opened liquid egg substitute keeps only 3 days refrigerated — a much shorter window than shell eggs, and the most surprising number in this category. Unopened, it keeps about 10 days, or its package date if that comes sooner.

Keep the carton closed and on a cold shelf, never in the door. Pour what you need and return it immediately.

Frozen egg substitute keeps about a year, and many brands are sold frozen. Thaw in the refrigerator and use it within a few days; do not refreeze.

Do not pour unused product back into the carton after it has been sitting out or come into contact with a bowl or utensil.

The three-day rule seems severe next to a shell egg's five weeks, and the contrast is instructive.

A shell egg is a sealed, single-portion package with its own antimicrobial defenses — lysozyme in the white, a physical barrier in the shell membrane, and a yolk isolated from the outside world. Liquid egg substitute has none of that. It is pasteurized liquid egg, usually whites with added color and stabilizers, poured into a shared carton.

Pasteurization is the key to both the safety and the short window. It destroys Salmonella, which is why liquid egg products are the safe choice for anything uncooked such as homemade mayonnaise, mousse, or Caesar dressing. But it does not sterilize, and it strips out none of what makes liquid egg an excellent bacterial medium: high protein, high moisture, and a near-neutral pH.

Opening the carton introduces air and organisms into a homogeneous liquid where anything that lands disperses through the whole volume immediately. There is no shell, no compartment, and no acidity to slow it.

Spoilage shows as a sour or sulfurous smell, thickening or sliminess, and any color change from the uniform pale yellow. Given how quickly it turns and how mild the early signs are, go by the calendar rather than the nose.