In the refrigerator:
Bacteria thrive on most meat unless it is kept below 4°C/40°F in the refrigerator. Cold temperatures reduce the rate at which bacteria multiply and the rate at which enzymes degrade the meat protein. Nevertheless, the bacteria are still partially active and will spoil the meat if it is stored for too long.
Uncooked meat must be stored separately from cooked meat and food that will not be heated before it is eaten. Raw meat loses fluid and blood, containing bacteria, while it is stored, and this could drip onto and contaminate other food stored nearby, resulting in food poisoning. For this reason, it should always be stored at the bottom of the refrigerator.
To preserve its freshness and colour, meat must be allowed to breathe. If it comes tightly wrapped, pierce the cling film or rewrap in oxygen-permeable cling film or paper and refrigerate for no longer than 2 or 3 days. Meat bought in oxygen-flushed sealed containers at a supermarket is best left intact as this packaging is designed to keep meat fresh as long as possible. Some cuts of meat are vacuum-packed, which will keep the meat fresh for several weeks. However, many chefs feel that vacuum packing is detrimental to the texture of meat.
In the freezer:
Meat can be kept for much longer if it is stored in the freezer at -18°C/0°F. Most bacteria responsible for meat spoilage require water and warmer temperatures to work actively and are therefore inhibited as long as the meat is frozen. However, meat can still oxidize when frozen, which is why thawed meat is often dull in colour. It is important to wrap the meat tightly before storing it in the freezer, to prevent the surface of the meat drying out, which would affect its taste and texture.
Although meat freezes well, when defrosted it will be of lower quality than fresh if ice crystals that might have formed, damage the muscle cell walls. When the meat is defrosted, liquid or water contained in the cells sometimes drains away to form a pool of fluid. The loss of fluid results in tougher, drier cooked meat. Meats containing a high proportion of unsaturated fats, such as lamb, pork and poultry, should be eaten within a few months of freezing, as the fats may become rancid. Beef may be frozen for 9 months as its fat is saturated and is less likely to deteriorate.