Effect of natural fermentation on milled rice grains: Physicochemical and functional properties of rice flour

This study examined the effects of natural fermentation on rice components to understand how fermentation affects the physicochemical and functional properties of rice flour. We found that natural fermentation for 72 h had almost no effect on the structural properties of rice starch and slightly affected the protein content and composition. The charged amino acid content of rice flour decreased after fermentation, while the surface hydrophobicity increased. The surface charge of rice flour increased from −12.7 mV before fermentation to +7.06 mV after 72 h of fermentation. The reduced protein content in fermented rice flour increased the gelatinization enthalpy of rice flour to a level similar to that of starch, and enhanced starch granule expansion, resulting in an increased peak viscosity and granule breakdown, but decreased final viscosity, setback, and pasting temperature. Differences in the protein composition, surface hydrophobicity, and surface charge between fermented and non-fermented rice flour explained the greater hardness of fermented rice flour. We conclude that natural fermentation can improve the functional properties of rice flour through protein modification on the starch granule surface.