Interactions between recrystallized rice starch and flavor molecules

Two flavor compounds in cooked rice—2,3-butanedione and 2-acetyl-1-pyrroline were selected as representative flavors that could respectively form B- and V-type crystal complexes with starch. Interactions between recrystallized starch and these flavor compounds were systematically investigated using Fourier-transform infrared (FT-IR), laser confocal micro-Raman (LCM-Raman) spectroscopy and 13C cross-polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR). Results of FT-IR and LCM-Raman showed that 2,3-butanedione and 2-acetyl-1-pyrroline molecules could interact with recrystallized starch via hydrogen bonding affecting the molecular water environment of starch but with different modes of action. 13C CP/MAS NMR results further indicated that flavor molecules affect the water distribution microenvironment and starch chains conformations in the recrystallized region. The 2-acetyl-1-pyrroline molecules could potentially enter the hydrophobic cavities of B- and V-type crystals, whereas 2,3-butanedione could only interact with the starch chains. These results could enrich knowledge on the flavor retention mechanisms of recrystallized starch.