Freezing and Food Safety

• Freezing preserves foods in several ways. For one thing, the low temperature slows -- but doesn't stop -- the natural enzymes that cause the tissues to break down over time. Freezing can also kill parasites, such as Trichina spiralis, which causes trichinosis, leaving the meat safer than it began. Finally, and most importantly, it stops the action of bacteria that can cause illness. This is crucial because most bacteria must reach a certain population, called the infective dose, before they can make you ill. Freezing prevents the bacteria from reproducing, and therefore from reaching the infective dose.

A Healthy Start

• The sooner your meats are frozen initially, the lower the bacterial population they'll contain. The safest of all are meats purchased already frozen from the packing plant, in part because they were frozen shortly after butchering and in part because commercial blast-freezing is fast. If you routinely buy extra meats or large packages specifically for freezing, package and freeze them as soon as possible after you get home from the store. The longer the meats remain in your refrigerator before freezing, the livelier their bacterial population can become.

Keeping It Safe

• If you want the option of refreezing your meats, you'll need to thaw them safely. The way to do this is by thawing in your refrigerator, which ensures that they remain at a safe temperature at all times. This minimizes bacterial grown, ensuring that the meat remains safe. You can safely thaw meats under cold running water, or in the microwave, but that creates opportunities for bacterial growth. Meats thawed through those methods should be cooked immediately and not refrozen. Meats should never be thawed at room temperature, under any circumstances.

That Quality Thing

• Although it's important, food safety isn't the only issue when you're thawing and refreezing meats. The moisture that fills the cells in muscle tissue behaves like any other water when it freezes, expanding and forming sharp-edged crystals. Those crystals tend to burst the cell walls, and when the meat is thawed some of its moisture is lost from those burst cells. If it's refrozen the damage becomes greater, because the moisture from already burst cells forms larger crystals and causes greater damage. As a result, twice-frozen meats tend to be tougher and drier.