Effect of cooking on the total antioxidant capacity and phenolic profile of some whole-meal African cereals

Background: At present, sorghum, fonio and millet are not placed as important commodities in the North American and European food basket, but their importance as ingredients in multigrain and gluten-free cereal products is highlighted. Therefore in this study the phenolic profile (evaluated by liquid chromatography/tandem mass spectrometry), total phenolic content (assessed by Folin-Ciocalteu assay) and total antioxidant capacity were measured in three African whole grains, i.e. sorghum (Sorghum bicolor ssp. bicolor), fonio (Digitaria exilis) and pearl millet (Pennisetum glaucum L.), before and after a cooking procedure. Results: After the cooking process, soluble phenolic acids increased significantly in sorghum, whereas bound ones and anthocyanins decreased significantly. In millet the cooking process significantly enhanced soluble phenolic acids without affecting those bound, whereas in fonio a slight but significant decrease in almost all soluble phenolic acidswas observed along with a significant increase in bound ones. Finally, the cooking process negatively affected both total phenolic content and total antioxidant capacity. Conclusion: This is one of the few reports dealing with the antioxidant compounds of these three African whole grains in which the effect of cooking was also evaluated. The data suggested that, to improve their antioxidant properties, specific cultivars should be selected and the cooking procedures carefully considered.