Functional and nutritional properties of infrared- and microwave heat-moisture-treated sorghum meals

Abstract

BACKGROUND AND OBJECTIVES : Starch modification using heat-moisture treatment (HMT) has been proven to influence starch functionality and nutritional properties as it can increase resistant starch content and reduce the glycemic index (GI). This study aims to determine the nutritional and functional properties of infrared (IR)- and microwave (MW) heat-moisture-treated (HMT) white and red non-tannin, and red tannin sorghum meals with the aim of further reducing the estimated GI. FINDINGS : All treated meals had significantly (p < .05) lower pasting peak viscosity than the untreated samples, possibly due to aggregate formation observed under the light microscope, restricting the starch from swelling to form a high-viscosity paste. There was a decrease in the percentage of starch hydrolysis between the sorghum types and a further decrease after HMT treatment. A significant difference was observed in the protein digestibility between the sorghum types, but not between the treatments. CONCLUSION : HMT with IR and MW further reduced the starch digestibility, possibly because of changes in the starch molecular configuration. SIGNIFICANCE AND NOVELTY : This study suggests that the changes in the starch functionality and nutritional properties of the HMT-treated sorghum meals can potentially be useful in the development of lower-GI sorghum foods. The results also differentiate the characteristics of sorghum types.