Protein Contents Determine the Thermal Stability and Gel Consistency of High-Amylose Milled Rice

Protein and starch are the two primary components of rice flour, significantly influencing their gelatinization and gel consistency. However, the role of protein in the gelatinization properties and gel consistency of high-starch starch remains unclear. Our study investigated the influence of protein on the gelatinization and gel consistency of high-amylose rice flour by analyzing six high-amylose rice varieties with differing protein levels. The results demonstrated that elevated protein content was associated with reduced breakdown (BD) and gel consistency. Additionally, a recombinant rice flour (RRF) system was developed by reintroducing extracted proteins into high-amylose rice flour in various ratios. The findings indicated that increasing protein proportions in the RRF system led to a marked decrease in gel consistency, accompanied by reductions in peak viscosity (PV), BD, final viscosity (FV), and setback (SB), while peak time (PeT) and pasting temperature (PaT) exhibited significant increases. Correlation analysis and microstructure observations support the hypothesis that proteins may enhance the stability of the paste by restricting the expansion of starch granules during gelatinization, which is related to the reduction in gel consistency. This study confirmed that protein content plays a significant role in determining the gel consistency of high-amylose rice, guiding the improvement of the quality of use or cultivating high-amylose rice suitable for processing.