Evaluation of solid state of rice flours produced by different milling processes using ATR-FTIR spectroscopy

This study evaluated the influence of the milling process on solid state of rice flours according to water activity using ATR-FTIR. A band at 1740 cm-1 attributed to the C=O stretching of lipids was detected for crystalline samples, and it disappeared at a high aw range. The CH band at 2930 cm-1 of crystalline samples gradually shifted to a higher wavenumber with aw. This band of the α-formed and wet-milled samples shifted to higher wavenumbers above 0.8 aw. A band due to OH stretching mode in the 3500–3000 cm-1 region did not shift with aw. The result obtained from IR spectra suggests that the parameter K calculated by Guggenheim–Anderson–de Boar (GAB) model reflected not only the interaction between water molecules but also the changes of state in solids. Consequently, the results from this study provide insights about the adsorption properties of non-ideal solids such as rice flour.