Effects of processing sorghum and millets on their phenolic phytochemicals and the implications of this to the health-enhancing properties of sorghum and millet food and beverage products.

Sorghum and millet grains are generally rich in phytochemicals, particularly various types of phenolics. However, the types and amounts vary greatly between and within species. The food-processing operations applied to these grains, i.e. dehulling and decortication, malting, fermentation and thermal processing, dramatically affect the quantity of phenolics present, most generally reducing them. Thus the levels of phytochemicals in sorghum and millet foods and beverages are usually considerably lower than in the grains. Notwithstanding this, there is considerable evidence that sorghum and millet foods and beverages have important functional and health-promoting effects, specifically antidiabetic, cardiovascular disease and cancer prevention, due to the actions of these phytochemicals. Also their lactic acid bacteria-fermented products may have probiotic effects related to their unique microflora. However, direct proof of these health-enhancing effects is lacking as most studies have been carried out on the grains or grain extracts and not the food and beverage products themselves, and also most research work has been in vitro or ex vivo and not in vivo. To provide the required evidence, better designed studies are needed. The sorghum and millet products should be fully characterised, especially their phytochemical composition. Most importantly, well-controlled human clinical studies and intervention trials are required.