Educate yourself about the differences between “sell by,” “best if used by” and “use by” dates that are imprinted on sour cream tubs. The “sell by” date informs the store how long it should display the sour cream for sale, according to the U.S. Department of Agriculture. Consumers should purchase sour cream before the “sell by” date. “Best if used by” is a quality measure; it tells you when the sour cream will be of the best quality and taste its best. The “use by” date is the last date that the sour cream should be consumed. Both the USDA and the Food and Drug Administration recommend that consumers follow the “use by” date on sour cream.

Interpret the “best if used by” date with caution. In general, if the sour cream is unopened, it will be safe in the refrigerator for two weeks after the “best if used by” date. Once the sour cream has been opened, it can be safe for one or two weeks after the date has passed. Note the operative words: “can be safe.” If a tub of sour cream has been left on a counter at room temperature for several hours, bacteria can fester and it will not be safe to eat, no matter what the “best if used by” date.

Heed a warning from Weill Cornell Medical College: There is "no absolute expiration date" that guarantees sour cream is safe prior to a "best if used by" date -- or that bacteria is festering immediately after that date. This is why the college calls upon consumers to rely on their common sense and senses and to follow safe food storage advice.

Judge the sour cream by its appearance. Look for an unusual amount of whey floating on the surface of the sour cream. Some whey is normal; an abundance is not. Inspect the sour cream for discoloration; moldy green or black areas as well as the bacterial colors of yellow, blue and pink are signs of spoilage. Discard such sour cream tubs immediately. Don’t confuse discoloration with separation, which is normal for sour cream. If your sour cream has separated, stir it with a spoon to return it to its normal consistency.

Smell the sour cream. An unfamiliar odor, beyond the normal “sour” aroma, is a sign of spoilage. Throw off-smelling sour cream away.

Taste just a little of the sour cream. A strange or bitter taste is a sign that the sour cream is bad and should not be fully consumed.

Trust your instincts and err on the side of caution. Or, as Georgia Giannopoulos, registered dietitian at Weill Cornell Medical Center says, “When in doubt, throw it out!”