Structure characteristics and physicochemical property of starch, dietary fiber, protein in purple corn flour modified by low temperature impact mill

The structural changes of macromolecules (starch, dietary fiber and protein) in purple corn flour (PCF) modified by a low temperature impact mill (LTIM) at different air classifier speed (ACS) were investigated. LTIM changed the multi-scale structure of starch, which was characterized by increased starch damage, stronger destruction of relative crystallinity (from 37.85 % to 15.53 %) and short-range ordered structure (R1047/1022, from 1.21 to 0.73) with the increased ACS. The structure of dietary fiber was also destroyed on multi-level, including decreased particle size, destructive morphology, and slightly changed crystalline structure. Additionally, LTIM showed high damage on the senior structure (surface hydrophobicity, disulfide bond, secondary structure) of protein. Due to the structure changes modified by LTIM, starch, dietary fiber and protein played different role on hydration property of PCF. Starch had positive effect, while dietary fiber and protein had negative effect. Our experimental results may provide valuable information for further analysis of other quality changes (oil holding capacity, cation exchange capacity, ability to produce high-quality dough or end-out products, etc.) of purple corn flour after LTIM treatment.