Bad ground beef typically smells pungent, putrid, sour, or rancid. It may have a strong, unpleasant odor that can be described as sour, ammonia-like, or similar to sulfur. Fresh ground beef usually has a neutral or slightly metallic (iron) smell, so any strong off-putting or foul odor is a clear sign of spoilage

. In summary, if ground beef smells bad, sour, rancid, or ammonia-like, it is spoiled and should be discarded to avoid foodborne illness. Trusting your nose is one of the best ways to determine if ground beef has gone bad