In the United States, sale of cow's milk is closely regulated to keep the public safe and prevent outbreaks of foodborne illness. The law requires that Grade A milk, sold in supermarkets, is properly pasteurized, a process that involves heating milk to destroy bacteria, followed by rapid cooling. Pasteurization is the only way to be sure that milk doesn't contain harmful bacteria. However, even pasteurized milk spoils rapidly when stored improperly.
Milk at Room Temperature
Never allow milk to sit out of the refrigerator at room temperature, even for a short time because disease-causing bacteria develops rapidly in temperatures above 45 degrees Fahrenheit. Pour milk into a glass or other serving container and then return the jug to the refrigerator immediately. Discard milk left at room temperature and never pour the warm milk back into the original container because it can contaminate the entire jug. Anybody can become ill from drinking improperly stored milk; elderly people, pregnant women, infants and chronically ill people, however, are most at risk.
Storing Fresh Milk
Use an appliance thermometer to monitor the temperature of your refrigerator because safe food storage of milk and other perishable food requires cooling between 34 F and 40 F. Check the temperature in several places in your refrigerator to determine the coldest spot, which is usually the area nearest the freezer compartment. When you store milk properly, the milk usually retains its flavor and quality for one to two weeks, or one to five days beyond the "use by" date stamped on the container. Don't overload your refrigerator, because proper cooling requires the air to circulate.
Buying Fresh Milk
Look closely at the date on the milk container and always buy milk that has the most recent date. Generally, supermarkets promptly remove outdated milk from the shelves. Do not purchase outdated milk or milk with a sour smell. Legally, stores must store milk at 45 F or lower. Purchase dairy products and other perishables last, and then go directly home and immediately put the products in the refrigerator. Never allow milk to sit in a hot car for any length of time.
Other Dairy Products
As a general rule, buttermilk, cream and half-and-half retain quality for one to two weeks, the same length of time as whole, low-fat or skim milk. Sour cream keeps for two to three weeks and yogurt is safe to eat for up to one month, when you properly store these in an airtight container in the coldest part of your refrigerator. Canned evaporated milk keeps for up to one year when stored in a cool, dry location. However, once opened, the storage life of canned milk is no different from that of fresh milk. Unopened nonfat dry milk retains quality for six months, with storage time dropping to three months, once you have opened the container. Once mixed with water, storage is the same as for fresh milk.
- Clemson Cooperative Extension: Safe Handling of Milk and Dairy Products
- University of Wisconsin Cooperative Extension: Keeping Food Safe
- Texas Agricultural Extension Service: Safe Home Food Storage
- National Dairy Council: Frequently Asked Questions
- University of Nebraska-Lincoln Extension: Refrigerated and Freezer Storage
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