Impact of steam explosion on Sorghum starch digestibility and physicochemical properties

Steam explosion (SE) treatment induced structural and compositional modifications in sorghum grains, synergistically enhancing the digestion-resistant properties of the sorghum flour through promoting interactions between constituents. However, the synergistic mechanism between starch and polyphenols in influencing these properties remains underexplored. Results established that SE treatment significantly improved the anti-digestive characteristics of sorghum flour, with polyphenols playing a pivotal role, as evidenced by comparisons with de-phenolized flour. SE treatment notably increased the content of bound phenolics, facilitating starch-polyphenol complexation and thereby elevating resistant starch (RS) content. Higher SE intensities induced starch gelatinization and amylose degradation, reducing starch viscosity. Specifically, RS content rose from 39.89 % (untreated) to 54.29 % (1.2 MPa, 120 s), while rapid digestible starch (RDS) decreased from 35.93 % to 23.00 % (1.2 MPa, 180 s). Moderate SE conditions (e.g., 1.2 MPa, 120 s) optimally balanced polyphenol content and starch structural changes, maximizing anti-digestive effects. Multi-scale structural analyses (SEM, XRD, FTIR) revealed that SE altered starch crystallinity, promoted V-type complex formation, and disrupted short-range molecular order. These findings demonstrate that SE enhances anti-digestive properties through physical starch modification, while the concurrent changes in polyphenol content may also contribute, though their specific role requires further investigation to assess overall processing suitability.