Sour, rancid, or otherwise off smell
Slimy, sticky, or unusually tacky surface
Discoloration such as yellowing, graying, or dark spots
Mold growth
Puffy or swollen package
Package leaking or damaged
Sour or bitter taste
Strange texture that is mushy, crumbly, or excessively dry
Excessive gas bubbles or fermentation signs in opened tofu
Passed the expiration date and has been stored improperly
Left out at room temperature for more than 2 hours
Been refrigerated too long after opening, especially more than 3 to 5 days