Study on the differences in the effects of sulfite and protease on the structure and processing quality of high purity corn starch

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This study aimed to investigate the effects of sulfite and protease treatments on the molecular structure and processing quality of starch. Analyses showed that starch purity exceeded 90 % for both extraction methods. Compared with protease-extracted starch, sulfite-extracted starch exhibited a 0.05 % reduction in residual protein content. Fourier-transform infrared (FTIR) spectroscopy demonstrated that sulfite treatment hydrolyzed starch granular-associated proteins (SGAPs), which enhanced molecular ordering within the starch matrix. Sulfite-extracted starch also had higher solubility (over 4.8 %) and swelling degree (over 11.29 g/g) than protease-extracted starch. Electron microscopy revealed protein residues on the surface of protease-extracted starch granules. Additionally, protease-extracted starch exhibited higher peak viscosity, trough viscosity, and final viscosity than sulfite-extracted starch, with a lower hydrolysis rate in the first 30 min. These findings provide a foundational basis for advancing the functional applications and molecular-level investigations of these two starch types. • The purity of starch extracted by sulfite method and protease method was more than 90 %. • H 2 SO 3 could hydrolyze SGAPs and thus increase the ordering degree of starch. • Protease starch preserves the native stable structure of the starch-protein and has anti-digestibility.