Influence of Fluidized Bed Jet Milling on Structural and Functional Properties of Normal Maize Starch

Normal maize starch samples with moisture contents of 11.24%, 6.18%, and 1.5% are ground using a fluidized bed jet mill at classifier frequencies of 2400, 3000, 3600, and 4200 to produce micronized starch powder. The changes in structural and functional properties of the starch after jet milling process are studied. The particle size of starch significantly (p < 0.05) decreases after jet milling and as the classifier frequency increases. Also, the bulk and tap density decreases; while the specific surface area increases and the flowability of the milled samples becomes quite poor as the classifier frequency increases. The microscopy analysis shows that the jet milling destroys the crystalline areas and promotes amorphous areas of starch granules. The micronized starch samples show a significant (p < 0.05) increase in their water solubility, swelling power, water and fat holding capacities, and pasting temperature compared with native starch. However, a decrease in viscosity parameters of starch is found after jet milling and as classifier frequency increases. The initial moisture content of starch shows a slight effect on the functional properties of the micronized starch. The obtained results suggest that modified starch can be produced by fluidized bed jet milling.