Cheddar

Opened cheddar keeps 3–4 weeks refrigerated and about six months unopened; it freezes for around six months.

Do not seal it in plastic film. Cheddar keeps best wrapped in cheese paper or wax paper, then placed loosely in a container in the crisper drawer. Plastic traps the moisture the cheese gives off, which makes the surface slimy and encourages mold, while also imparting a plastic flavor over time.

A block keeps far better than shreds. Pre-shredded cheddar has many times the surface area, dries out quickly, and is contaminated throughout the moment mold arrives — which is why the storage advice for it is so much stricter. Buy blocks and grate as needed if you want the full window.

Frozen cheddar becomes crumbly and loses its slicing texture as ice crystals rupture the protein network. It melts perfectly well, so freeze it destined for cooking rather than for a cheese board.

Cheddar is a hard, aged, pressed cheese, and each of those words is a preservation step. Pressing expels whey and lowers moisture to around 35%. Salting reduces water activity further. Aging drops the pH and allows the protein structure to tighten. The result is a body that bacteria find genuinely difficult to grow in — which is why cheddar keeps for weeks where fresh cheese keeps for days, and why some aged cheddars keep for years.

That density is precisely what makes the one-inch rule valid here. Mold on a firm cheddar cannot send its filaments far into the low-moisture body, so the USDA advises cutting at least one inch around and below the spot, keeping the knife clear of the mold so you do not carry it into the clean cheese. The remainder is fine to eat.

This does not apply to shredded or sliced cheddar — discard those entirely at the first mold.

Two harmless things are often mistaken for spoilage. White crunchy crystals in aged cheddar are calcium lactate, a marker of proper aging rather than a defect. And a dry, darkened, slightly waxy surface on a cut face is simple dehydration — trim it and the cheese beneath is fine.

Genuine warnings: pink, black, or fuzzy colored mold, an ammonia smell, and a slimy surface on a cheese that should be dry.