Beef that is spoiled will start to turn gray or brown in color, have a slimy feel and will smell sour. Once beef starts to lose its reddish color, it is best to throw it away to practice proper hygiene. Even if the beef is not completely spoiled by the time it turns brown, the taste of the meat will be different and often less enjoyable to eat.
It is important to avoid eating spoiled beef whenever possible. There is a good chance of getting food poisoning after eating spoiled beef. Some of the symptoms that go along with food poisoning include watery diarrhea, vomiting, fever, belly cramps and nausea.
Beef does not have to be spoiled to taste bad. Beef that has become freezer burned is often just as inedible as spoiled beef. To tell if beef is freezer burned, look for dull white patches of ice. These patches of ice look different than other ice because patches form in the actual meat itself.
Sometimes freezer burned beef is salvageable by cutting out the freezer burned spot and removing about 1 inch of meat around that area.
Cooking spoiled beef does not make it any safer to eat. Bacteria, such as E.coli, grows in meat even when it is frozen. Cooking the beef to proper temperatures kills the bacteria but toxins often still remain. This is why it is better to throw away spoiled meat.