If changes color when air hits it. Look in your supermarkets sometimes they are selling old meat for fresh. The first layer is nice and color coated with red ink and the ones underneath are light brown or brown. Unless if it smells putrid and has a glossy white goo on it. Don't eat it. The best way to find out if the beef is bad. Give it a rinse if it's steak. Wash the ground beef in its true form, do not break it apart whatsoever. Cut the in the middle if its red or pink its probably ok!. The same for the ground beef. Then put a piece on the hot skillet with hot oil to seer the top if its a steak, and do the same for the ground beef. Smell and taste and let your survival instincts do the rest. If it still smells chances are its bad. If it doesn't you can probably eat as long as you cook to the right temperature where the germs or bacteria are killed. In other words very high heat and make sure you cut the steak in squares and cook it in a sauce for awhile. The the same for the ground meat cook first high temperature, then cook with vegetables and a liquid and let simmer for a while. That's the best I can do, but use your own judgement to the meat. Oh! I forgot if the meat is only brown on top take the brown part off and cook the rest like I mentioned above.