【正文】 s the growth of microanisms that cause both food spoilage and foodborne illness. Once thawed, however, these microbes can again bee active, multiplying under the right conditions to levels that can lead to foodborne illness. Since they will then grow at about the same rate as microanisms on fresh food, handle thawed items as you would any perishable. Trichina and other parasites can be destroyed by subzero freezing temperatures. However, very strict governmentsupervised conditions must be met. It is not remended to rely on home freezing to destroy trichina. Through cooking will destroy all parasites. NUTRIENT VALUE The freezing process itself does not destroy nutrients. In meat and poultry products, there is little change in nutrient value during freezer storage. PACKAGING Proper packaging helps maintain quality and prevent freezer burn. It is safe to freeze meat or poultry directly in its supermarket wrapping, but this type of wrap is permeable to air. Unless you will be using the food in a month or two, overwrap these packages as you would any food for longterm storage using airtight heavyduty foil, plastic wrap or freezer paper, or place the package inside a plastic bag. Use these materials or airtight freezer containers to repackage family packs into smaller amounts or freeze foods from opened packages. It is not necessary to rinse meat and poultry before freezing. Freeze unopened vacuum packages as is. If you notice that a package has accidentally torn or has opened while food is in the freezer, it is still safe to use。 merely overwrap or rewrap it. 山東建筑大學(xué)畢業(yè)設(shè)計 外文文獻(xiàn)及譯文 2 FREEZER BURN Freezer burn does not make food unsafe, merely dry in spots. It appears as grayishbrown leathery spots and is caused by air reaching the surface of the food. Cut freezerburned portions away either before or after cooking the food. Heavily freezerburned foods may have to be discarded for quality reasons. COLOR CHANGES Color changes can occur in frozen foods. The bright red color of meat as purchased usually turns dark or pale brown depending on its variety. This may be due to lack of oxygen, freezer burn or abnormally long storage. Freezing doesn’t usually cause color changes in poultry. However, the bones and the meat near them can bee dark. Bone darkening results when pigment seeps through the porous bones of young poultry into the surrounding tissues when the poultry meat is frozen and thawed. FREEZE RAPIDLY Freeze food as quickly as possible to maintain its quality. Slow freezing creates large, disruptive ice crystals. During thawing, they damage the cells and cause meat to drip or lose juiciness. Ideally, food 2 inches thick should freeze pletely in about two hours. If your home freezer has a quickfreeze shelf, use it. Never stack packages to be frozen. Instead, spread them out in one layer on the shelves, stacking them only after frozen solid. REFRIGERATOR FREEZERS If a refrigerator freezing partment can’t maintain 0 ℃ , or if the door is opened frequently, use it only for shortterm food storage. Eat those foods as soon as possible for best quality. Use a freestanding freezer set at 0 ℃ or below for longterm storage of frozen foods. Keep a thermometer in your freezing partment or freezer to check the temperature. LENGTH OF TIME 山東建筑大學(xué)畢業(yè)設(shè)計 外文文獻(xiàn)及譯文 3 Because freezing keeps food safe almost indefinitely, remended storage times are for quality only. (See freezer storage chart below.) If a food is not listed on the chart, you may determine its quality after defrosting. First check the odor. Some foods will develop a rancid or off odor when frozen too long and should be discarded. Some may not look pictureperfect or be of high enough quality to serve alone, but may be edible。 cover with water and freeze. To prevent evaporation of the ice, wrap the container in freezer paper after it is frozen, label and freeze. 山東建筑大學(xué)畢業(yè)設(shè)計 外文文獻(xiàn)及譯文 5 Fish Roe: Thoroughly wash and package in freezer containers or bags and boxes, leaving 1 inch head space. Seal and freeze. FREEZING SHELLFISH Clams: Clams can be frozen either in the shell or shucked. To freeze the clams in the shell, simply place the live clams in moisture and vaporresistant bags. Press out excess air and freeze. To freeze the clam meat, shuck the clams, then clean and wash the meat thoroughly. Drain and pack in freezer containers, leaving 1 inch headspace. Seal, label and freeze. Crabs: Select only live crabs to prepare for freezing. Crab freezes better if not picked before freezing. Simply remove the back, legs, entrails and gills either before or after boiling the crab for five minutes. (Be sure to cool the crab quickly after it is cooked.) The claws and body or core of the crab that still contains the meat should then be wrapped or iceglazed and wrapped in freezer wrap or paper. Seal, label and freeze. Lobster: For best quality, lobster should be frozen uncooked. Freeze the lobster whole, or clean it and freeze just the shell portions that contain the edible meat. (Some lobsters have large front claws that contain edible meat, while others have edible meat mainly in the tail section.) Freeze lobster in the shell, to help keep the meat from drying out. Simply wrap the whole lobster or lobster portions in moisture and vaporresistant wrapping and freeze. Lobster can be cooked and then frozen, but the quality will not be as good. Oysters: Oysters that are still in the shell should only be frozen live. A live oyster will keep its shell tightly closed or will close when tapped. If you have plenty of freezer space and want to freeze the oysters in the shell, simply wash the shells thoroughly and place in moisture and vaporresistant bags. Shuck the oysters to save freezer space. First, wash the oyster shells, discarding any that have died. Shuck oysters into a strai