Sour, rotten, or ammonia-like smell
Slimy or sticky surface
Gray, green, brown, or otherwise unusual discoloration
Dull appearance instead of fresh, bright color
Off, bitter, or unpleasant taste
Gas or bloating in sealed packaging
Package leaking, puffed up, or damaged
Mold growth
Texture that feels tacky, mushy, or excessively dry
Meat past its use-by or expiration date
Strong odor after cooking
Visible spoilage spots or unusual film on the surface