In vitro starch digestibility of maize flour and maize extruded noodles based on different particle-size effects

In this study, the particle characteristics of the bimodal distribution of maize flour were utilized to screen maize flour with different grinding degrees. The changes in the digestibility characteristics of maize flour and extruded noodles were compared under the effects of grinding size and screening size. Under the effect of grinding size, the decrease in particle size was accompanied by an increase in the specific surface area and damaged starch contents of maize flour, enhanced the hydration ability of maize flour. And the digestion rate constants of raw flour and cooked flour increased from 0.0278, 0.0646 to 0.0514 and 0.0847, respectively. The digestion rate constant of extruded noodles increased from 0.0088 to 0.0097. Under the effect of screening size, compared to maize large particle flour (LF), small particle flour (SF) had higher total and damaged starch content, higher peak viscosity, and faster starch digestion. However, the digestion rate was lower after cooking. LF contained a higher protein content, and the prepared extruded noodles had thicker edges and a lower digestion rate. Therefore, SF after screening is more suitable for flour products with a low-glycemic index (GI), while LF is more suitable for preparing extruded noodles with a low-GI.