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Tannins of Grain Sorghum: Luteoforol (Leucoluteolinidin), 3′,4,4′,5,7‐Pentahydroxyflavan
Author(s) -
BATESMITH E. C.,
RAŠPER V.
Publication year - 1969
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1969.tb00919.x
Subject(s) - tannin , sorghum , food science , chemistry , lightness , tannic acid , proanthocyanidin , anthocyanin , wine color , agronomy , polyphenol , biology , biochemistry , organic chemistry , physics , optics , antioxidant
SUMMARY– The principal tannin of sorghum is a leuco‐anthocyanin yielding luteolinidin (3′,4′,5,7‐tetrahydroxy‐flavylium) when heated with mineral acid. The precursor, luteoforol, has most of the properties of 3′,4,4′,5,7‐penta‐hydroxyflavan prepared by reduction of eriodictyol. Luteoforol, when treated with concentrated mineral acid in the cold, gives a purple color with Λ max 550nm. A method for the determination of luteoforol in sorghum, based on this property, is described. The results with a number of varieties of sorghum are compared with those obtained by the AOAC Folin‐Denis method. The contribution of luteoforol to the “tannin” so determined varies from 1 to < 25%. Except for one sample of Kaffir corn, which contained leucocyanidin as well as luteoforol, no other tannins were detected. The “tannin” content varied widely, (from 0.05 to 0.67% as tannic acid), a white‐skinned variety having the least. The uniformity of commercial samples can be rapidly evaluated by single‐grain determinations of luteoforol.