2,3,5-Triphenyltetrazolium chloride

2,3,5-triphenyltetrazolium chloride (TTC) is a dye largely used for enumeration of microbial colonies in solid culture media, being a key component of the dry rehydratable film system used for microbiological analysis of food. This dye is colorless in the oxidized form and red when reduced by microorganisms, due to formation of formazan. Live microorganisms reduce TTC by enzymatic action, forming red color formazan that is kept inside granules in the cells.

2,3,5-triphenyltetrazolium chloride (TTC) is an indicator recommended for the microbiological analysis of food.