Ground beef makes a tasty burger, meatloaf or pot of chili, but not if it’s past its prime. Whether you’re making patties to toss on the grill or cooking the beef for tacos, know the warning signs of spoiled beef.

Common warning signs tell you when to toss, rather than prepare, ground beef. You should not consume any meat with a foul odor or sticky or slimy film. Visible mold growth also indicates bad beef.

Fresh ground beef has a clean odor and soft texture. Look on the package for a valid sell-by date, but recognize that these dates are really designed for the seller. The United States Department of Agriculture recommends that you cook or freeze ground beef within two days of buying it.

When meat ages and gets exposed to air, its color changes -- but that doesn’t always mean it's bad. Ground beef that has darkened or gone quite pale should be examined, though, for other signs of spoilage. A grayish interior or darkened exterior does not automatically mean the meat is bad, but if odor or slime accompany the color change, toss it.

The pathogens salmonella, campylobacotr, listeria, E.coli and staphylococcus can all infiltrate ground beef. The beef can be exposed to the pathogens when meat is ground, and they can increase exponentially when the temperature is between 40 and 140 F. No clear visible signs tell you that meat has been infected with a food-borne pathogen that can make you ill.

Refrigerate or freeze ground beef as soon as you get it home from the store. Always cook ground beef to an internal temperature of 165 F -- never partially cook it, which only invites bacterial growth. In summer, do not leave raw patties out by the grill as it heats up; likewise, don't leave cooked patties out for more than an hour. If you're defrosting frozen ground beef, place it in the refrigerator or use the microwave's defrost setting. You may also place tightly wrapped frozen ground beef in a bowl of cold water for quick defrosting. Never leave frozen ground beef out on the counter or in an empty sink to thaw.