Cereal Chem 63:4-8   |  VIEW ARTICLE
Effect of Genotype on Tannins and Phenols of Sorghum.

D. H. Hahn and L. W. Rooney. Copyright 1986 by the American Association of Cereal Chemists, Inc. 

The color and the phenols of sorghum pericarp and testa are controlled by the R, Y, B1, B2 and S genes. Relatively pure fractions of pericarp, testa, and endosperm were isolated by abrasive milling, sieving, and air flotation from six genetically diverse sorghum varieties grown at two locations. Ground whole grain, pericarp, testa, and endosperm were extracted sequentially with methanol, acidic methanol (1% HCl), and dimethylformamide. The phenolic compounds were measured and characterized by four methods: vanillin assay, Folin-Ciocalteu assay, anthocyanidin pigment determination, and relative degree of polymerization (RDP). The endosperm did not contain significant amounts of extractable phenols. R and Y genes did not affect the level of Folin-Ciocalteu positive phenols or tannins in group I sorghums (b1b2B1-, B1-b2b2, b1b1b2b2). Dominant R and Y greatly increased the levels of anthocyanidin pigments in group I (b1b1B2-) and II (B1-B2-ss) sorghums. Group II sorghums with a red pericarp (R-Y-B1-B2-ss) had higher levels of Folin-Ciocalteu-positive phenols or tannins in group I sorghums (b1b2B1-, B1-b2b2), with a white pericarp (R-yy-B1-B2-ss). The RDP of the tannins in the testa was not affected by R or Y, but the tannins in the pericarp of group II sorghums with a white pericarp had a higher RDP. The level of tannins in the testa of group III sorghums was not affected by R and Y, but more Folin-Ciocalteu phenols were extracted with methanol from the testa when the pericarp was white (R-yy-B1-B2-S). The pericarp and testa of group III sorghums (B1-B2-S-) had similar levels of anthocyanidin pigments. Group III sorghums had higher levels of Folin-Ciocalteu phenols and tannins in the whole grain, pericarp, and testa fractions than group II sorghums. The S gene did not affect the RDP of the tannins but did affect the extractability.