Cheese

Cheese storage divides on one variable: moisture content. Hard cheeses like cheddar and parmesan keep 3–4 weeks opened; soft cheeses like brie, fresh mozzarella, and queso fresco keep about a week.

The most common mistake is wrapping cheese in plastic film. Cheese is alive and needs to breathe; sealed tightly in plastic it suffocates, sweats, and takes on a plastic taste. Cheese paper or wax paper, then loosely in a container, is much better — it lets moisture escape while stopping the cheese drying out entirely.

Store cheese in the vegetable crisper or a dedicated drawer, which is the most humid and most temperature-stable part of the refrigerator. Cold, dry refrigerator air is what cracks and hardens a cut face.

Hard cheese freezes for about six months but comes out crumbly, since ice crystals rupture the structure — fine for cooking, poor for a cheese board. Soft cheeses do not freeze usefully at all.

Cheese is a preservation technology. Turning milk into cheese removes most of the water, adds salt, and drops the pH through bacterial fermentation — three independent barriers to spoilage. How many of those barriers a given cheese has determines how long it keeps.

A hard aged cheese like parmesan has very little free water, a great deal of salt, and a dense protein structure. Bacteria struggle to grow in it at all, and it can sit for years. A fresh high-moisture cheese like ricotta or queso fresco has had almost none of that done to it, and it behaves much like the milk it came from.

This difference drives the mold rule, which is the most practically useful thing to know about cheese. On a firm or hard cheese, mold cannot penetrate far into the dense low-moisture body, so the USDA advises cutting at least one inch around and below the spot, keeping the knife out of the mold itself. The rest of the block is fine.

On soft, shredded, sliced, or crumbled cheese, discard the whole package. High moisture lets mold filaments spread invisibly through the mass, and the increased surface area of shredded cheese means contamination is everywhere at once.

Other signs: ammonia smell (over-ripening, normal in small amounts on bloomy-rind cheese but not elsewhere), sliminess on a cheese that should be dry, and pink or black mold, which is never acceptable on any cheese.

Cheese packaging often shows "best by" or "sell by" dating. Those are quality or inventory dates for most cheeses, not automatic safety kill switches. Soft cheeses still need the short opened windows on this page; hard blocks keep longer. Soft cheese with mold: discard it. Hard cheese: you may cut mold away with a 1-inch margin per USDA advice — that is about mold growth patterns, not about ignoring a sour smell.