‘Méi biàn’ literally combines ‘méi’ (mold, mildew) and ‘biàn’ (change, transformation), referring specifically to the physical and chemical deterioration of organic materials—especially food, grains, herbs, or stored goods—caused by mold growth. It is not just surface discoloration but indicates spoilage that may produce harmful mycotoxins, making the substance unsafe for consumption or use.

This term is commonly used in agricultural, food safety, pharmaceutical, and traditional Chinese medicine contexts. Unlike general terms like ‘fā méi’ (to get moldy), ‘méi biàn’ emphasizes the *result* of mold activity—the spoiled, degraded state—and often carries implications of loss, contamination, or health risk. It appears frequently in quality control reports, storage guidelines, and public health advisories.