Thermodynamic drivers of rice glutenin Assembly: Multiscale analysis of Hierarchical structure and intermolecular bonding

Abstract

To investigate the effect of temperature on rice glutenin (RG), four rice varieties (WYD 4, SJ 20, LD 28, and JND 738) were selected and subjected to heat treatment at temperatures ranging from 50 °C to 90 °C. Following heat treatment, RG exhibited a rough, spongy network structure, with high storage modulus (G′) and loss modulus (G") values, indicating gel-like properties. Both G′ and G" decreased after heating. However, tan δ decreased while elasticity increased upon heating, with the opposite effects observed after cooling. As the temperature increased, the average particle size of the four types of RG expanded, suggesting aggregation. Fourier transform infrared (FTIR) spectroscopy confirmed that an ordered structure predominated within the secondary structure of RG. Heat treatment initially increased and then decreased the fluorescence intensity and surface hydrophobicity. With rising temperatures, free sulfhydryl groups were converted into disulfide bonds, reaching the highest concentration at 80 °C (335.87 μmol/g、256.72 μmol/g、277.27 μmol/g、338.14 μmol/g). These findings indicate significant alterations in the conformation and interactions among RG aggregates between 70 °C and 80 °C, which suggests that this range is the key transition temperature for the functional properties of RG. These finding contribute to optimizing temperature control in grain processing, offering a theoretical foundation for improving grain-based product design. These results are significant for enhancing the quality of RG-related products and guiding the development of novel formulations.