Package Dates

• A few of the package dates you find on your groceries are required by law to ensure food safety. However, in most cases what you see is a freshness or "use-by" date, which has little to do with food safety. Usually, that date is the manufacturer's conservative estimate of how long the product retains its best flavor and texture, and a substantial margin of error is built in. If the "use-by" date actually reflected the end of the product's useful life, consumers would often taste the product at less than its best. No manufacturer wants that to happen.

Original Packaging

• Firm cheeses such as cheddar are almost always sold as a solid brick, carefully sealed in airtight packaging. The absence of oxygen inside the packaging creates unfavorable conditions for the growth of undesirable molds and bacteria. As long as the package remains sealed and the cheese is properly refrigerated, it can remain flawless for up to six months. For longer storage, you can freeze the cheddar, which extends its shelf life almost indefinitely.

Opened Packages

• Once you've opened your cheddar, its remaining shelf life is very much in your hands. Once the seal is broken, your cheese needs to "breathe," so wrap it first in wax paper or parchment paper. After that it can be packaged loosely in a plastic bag or plastic film wrap. Depending on how often you open and use it, your cheese should last for up to a month. This technique also works for cheese you've bought at the deli as store-cut pieces, so rewrap them as soon as you get home.

Danger Signs

• If your wrappings are too loose, your cheddar might develop a dark, dried spot where the air got in. Grate these spots into sauces, in which they'll reabsorb the moisture they've lost, or simply trim them off with a knife and discard them. If something unidentifiable drips onto your cheese and is absorbed, a high risk of bacterial contamination exists, and you should discard the cheese. If your cheddar shows visible mold on the surface, consider it unsafe. You'll have to cut away a full inch of cheddar on all sides to remove the mold because it sends filaments deeper into the cheese. If your piece of cheddar isn't large enough to do that, discard it.