Ricotta

Opened ricotta keeps about 5–7 days refrigerated. It does not freeze well.

Keep the lid tight and the container on a cold shelf. Ricotta is very wet and very mild, and it takes on refrigerator odors faster than almost any other cheese.

Do not drain off the liquid that separates. It protects the curds from air, and stirring it back in restores the texture. If ricotta has become watery on top, tip it off only if the recipe requires a drier cheese.

Always use a clean spoon. Ricotta's near-neutral pH means anything you introduce grows readily.

Freezing turns ricotta grainy and weeping as the delicate curd structure collapses. Thawed ricotta is acceptable stirred into lasagna or baked into a filling, and poor eaten as it is.

Ricotta is not technically a cheese at all in the usual sense. It is made from whey — the liquid left over from making other cheeses — reheated until the remaining proteins coagulate. The name means "recooked".

That origin explains its short life. Ricotta has none of cheese's preservation mechanisms: it is not pressed, so it holds enormous amounts of water; it is barely salted; it is not aged; and its pH is close to neutral rather than acidic. It is essentially a wet, mild, protein-rich curd, which puts it among the most perishable items in the dairy case despite being sold alongside cheeses that keep for months.

Any mold means discard the entire container. The one-inch rule for hard cheese depends on a dense, dry body that mold cannot penetrate; ricotta is the opposite of that in every respect.

The clearest early signal is smell. Fresh ricotta smells faintly sweet and milky; as it turns it becomes sour and sharp, and the change is noticeable well before anything is visible.

Watch also for a pink or yellow tinge, a texture that has gone slimy rather than granular, and liquid that has turned thick or ropy instead of thin and clear.