Use of γ-irradiation to alleviate the poor protein digestibility of sorghum porridge

One limitation to the use of sorghum as a food is that its proteins become more indigestible on wet-cooking, primarily through the formation of disulphide-linked enzymatically resistant protein polymers. Irradiation can modify bonds involved in protein secondary structure. The effects of irradiation (10 and 50 kGy) of dry and wet sorghum and maize flours on the digestibility and solubility of their proteins, when further cooked into porridge, were investigated. Irradiation of sorghum flour, followed by cooking, alleviated the adverse effect of cooking on sorghum protein digestibility. Maize porridge digestibility was unaffected by irradiation of dry flour but decreased with wet-irradiation. Increase in digestibility was not accompanied by an increase in protein solubility, suggesting that it was probably related to modification of protein structure, allowing better access to proteolytic enzymes. Maillard reactions and protein aggregation, at high doses, negatively affected digestibility. Polyphenols influenced the effects of irradiation. (C) 2004 Elsevier Ltd. All rights reserved.