Effect of Foxtail Millet Flours with Different Particle Sizes on Rheological Properties of Dough and Texture Characteristics of Steamed Bread

This work was undertaken in order to study the effects of the addition of foxtail millet flour on the rheological properties of dough and the textural properties of steamed bread. The damage starch content and pasting characteristics of waxy and non-waxy foxtail millet flours with different particle sizes were analyzed using a damaged starch tester and a rapid viscosity analyzer. The rheological characteristics of doughs made from blends of wheat and foxtail millet flour were measured using a rheometer and the microstructure was observed using a scanning electron microscope (SEM). The texture characteristics of steamed breads made from wheat-foxtail millet doughs were measured using a texture analyzer. The results showed that the iodine absorption rate of damaged starch increased with decreasing millet flour particle size for most cultivars (except Jigu 39 and Huihua Jinmi). The peak viscosity, trough viscosity, final viscosity and setback value of nonwaxy millet flour were larger than those of waxy millet flour at the same particle size, depending on the ratio of amylopectin to amylose. Rheological studies showed that the storage and loss moduli generally increased with increasing angular frequency for most cultivars except Huihua Jinmi and Jigu 39. SEM observation revealed that the addition of millet flour made the dough structure looser. The addition of millet flour negatively affected the hardness, chewiness and springiness of steamed bread to a certain extent. Principal component analysis (PCA) showed that the chewiness of steamed bread and the damaged starch, peak viscosity, trough viscosity, final viscosity, disintegration value and setback value of millet flour are useful indicators to distinguish foxtail millet flours and steamed breads from waxy and non-waxy cultivars.