Swiss Cheese

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

Wrap it in wax or cheese paper rather than plastic film, and keep it in the crisper. Swiss is a semi-hard cheese with moderate moisture, so it needs to breathe but also dries out faster than a parmesan would.

Sliced Swiss from a deli counter is more perishable than a block, since slicing multiplies the exposed surface. Keep slices interleaved and tightly covered, and expect closer to two weeks than four.

Freezing makes Swiss crumbly and prone to breaking at the holes, which is a real drawback for a cheese usually wanted in slices. Freeze it for cooking rather than for sandwiches.

The holes in Swiss cheese are the most interesting thing about how it is made, and they are deliberate biology.

A third bacterial culture, Propionibacterium freudenreichii, is added along with the usual starters. During the warm-room ripening stage it consumes lactic acid produced by the other bacteria and releases carbon dioxide. That gas cannot escape the elastic curd, so it collects into bubbles — the "eyes" — and the propionic acid it also produces gives Swiss its characteristic sweet, nutty flavor.

So the holes, the flavor, and the texture all come from the same organism, and a Swiss with no eyes was simply ripened differently rather than being defective.

For storage, Swiss behaves as a semi-hard cheese: firmer and drier than mozzarella, wetter than parmesan. The one-inch rule applies to a solid block — cut an inch around and below any mold and use the remainder. Sliced or shredded Swiss should be discarded at the first mold.

Watch for a slimy surface, ammonia smell, or pink and black molds. A dried, darkened cut face is dehydration and can be trimmed. Moisture pooling inside the eyes of a cut block is normal condensation rather than a spoilage sign.