Sour smell that is unusually sharp, rancid, or rotten
Mold growth on the surface or around the container
Pink, green, blue, or black discoloration
Thick clumps, curdling, or separation that does not mix back together
Slimy or stringy texture
Bitter, off, or spoiled taste
Container is swollen, leaking, or damaged
Expired by a long time and has been opened for several days past the recommended storage time
Any signs of gas buildup or fizzing when opened