Effect of dry and wet heating and extrusion treatments on the phytochemical, antioxidant activity, techno-functional and nutritional properties of red and white sorghum flour

• Effects of dry heat (DHT), heat-moisture (HMT) and extrusion treatments (EXT) on the properties of white and red sorghum flour. • Only red sorghum flour contains tannin, and all treatments have resulted in a significant reduction in its content. • HMT and EXT led to increase in antioxidant compounds, while the content of phenolic decreased after EXT. • HMT samples could retain higher crystallinity, short-range ordered structure of starch. • EXT process had preferentially damaged the starch structure. Sorghum ( Sorghum bicolor (L.) Moench) is a widely cultivated gluten-free cereal grain; however, it requires appropriate processing to reduce anti-nutritional factors and to enhance its nutritional quality and functional properties. This study investigates the impacts of dry-heat treatment (DHT; 100°C, 1 hour), moist-heat treatment (HMT; 110°C, 6 hours), and extrusion treatment (EXT) on chemical composition, minerals, phytochemicals, structural properties, gelation behavior, and starch digestibility of white and red sorghum flours. Minerals, phenolic content and antioxidant activities were consistently higher in red sorghum flour compared to the white one. DHT and HMT increased the phenolic content, whereas EXT notably decreased it by 42.75 % in white sorghum and 23.06 % in red sorghum flour. Conversely, antioxidant activities significantly improved after HMT and EXT treatments. Structural analyses indicated that EXT primarily caused starch granule breakdown, while HMT favored starch-lipid complex formation. HMT produced optimal gel structures in white sorghum flour, whereas both HMT and EXT resulted in liquid states in red sorghum flour, which is unsuitable for rheological assessments. DHT and EXT exhibited the most significant effects in enhancing the resistant starch (RS) content. The results demonstrate that DHT and HMT can cost-effectively modulate starch functionality and the techno-nutritional attributes of sorghum, whereas EXT flour is particularly suited to industrial applications, including infant foods, porridges, and noodle products.