The tannin and related pigments in the red skins (Testa) of peanut kernels

Summary The red skins of peanut kernels contain a catecholtype tannin. The purified tannin represented about 7% of the weight of the skins. Much smaller quantities of phlobaphene and so-called “leuco-anthocyanic chromogen” were isolated from the skins. Some evidence of the presence of traces of a flavonic-type pigment was obtained. Spectrophotometric investigations of the isolated tannin, phlobaphene, and “leuco-anthocyanic chromogen” indicated a close relationship of the three pigments. The tannin gave a water-soluble red pigment when refluxed with alcoholic hydrochloric acid. This pigment exhibited certain properties which are indicative of an oxonium-type structure. The elementary analyses and certain properties of the isolated tannin and related pigments were considerably different from those reported by previous investigators. The amorphous nature of these substances makes chemical investigation difficult. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.