Sour, musty, or rancid smell
Discoloration or unusual dark spots
Clumping from moisture
Presence of insects, larvae, or webbing
Mold growth
Bitter, off, or stale taste
Texture feels damp or sticky
Package is damaged, open, or has signs of pests
Past the recommended storage time
Rancid odor in whole wheat or nut-based flours
Strange color change compared with normal flour
Visible contamination or foreign particles