As part of polyphenolic acids, tannic acid or gallotannin has many useful properties, such as the ability to form strong complexes with metals and proteins. This makes it useful for improving the composition and taste of food.
Tannic acid is also a very good antioxidant. Therefore it is used in particular in the formulation of animal feed.
Gallotannin is also used for leather protection (tanning) and textile processing, as a rust stabilizer, corrosion inhibitor and for clarification of beer and wine.