Effect of rice protein on the water mobility, water migration and microstructure of rice starch during retrogradation

The effects of rice protein on the water mobility, water migration and microstructure of rice starch during retrogradation were investigated by low field-nuclear magnetic resonance (LF-NMR), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The addition of rice protein limited the migration of water in rice starch gels and delayed the decrease of the spin-spin relaxation time during storage. The nuclear magnetic imaging showed that the gel without rice protein shrank when it was stored for 7 days, while the gel with rice protein did not change significantly. The SEM indicated that the gel with rice protein had a tighter and more uniform structure than the gel without rice protein. Microstructure analysis proved that adding rice protein could inhibit starch recrystallization, and the inhibitory effect was dependent on the concentration of rice protein. The inhibitory effect of rice protein on the retrogradation of rice starch was hypothesized to be mainly due to the addition of rice protein imported the space restriction, which reduced the cross-linking of starch molecules to form an ordered structure, inhibited the moisture migration in the gel, and enhanced the water-holding capacity of starch gels.