Effect of extrusion cooking and simulated invitro gastrointestinal digestion on condensed tannins and radical scavenging activity of type II and type III whole grain sorghum

The effect of extrusion cooking and simulated invitro gastrointestinal digestion on proanthocyanidins in type II and III tannin sorghums was studied. Extrusion cooking was performed at different feed moisture levels (2Lh(-1), 3Lh(-1), 5Lh(-1) and 8Lh(-1)), with a barrel temperature of 150 degrees C followed by invitro gastrointestinal digestion. Extrusion cooked samples had lower total phenols, tannin content and radical scavenging properties than unprocessed tannin sorghum flour. For extrudates, there was progressive increase in total phenols and tannin content with increase in feed moisture. Extrusion cooked samples had increased proportion of dimers and decreased oligomers in the two tannin sorghums. Gastric and duodenal digests of the extrudates contained high proportions of monomers and dimers and some oligomeric proanthocyanidin species. Undigested porridges, gastric and duodenal digests inhibited radical-induced oxidative DNA damage. Extruded tannin sorghum may have health-promoting potential in relation to combating chronic diseases associated with oxidative stress.