Effect of thermal sterilization intensity on starch composition, structure and in vitro hydrolysis behavior of chestnuts

Thermal sterilization is essential for ensuring the safety of packaged chestnuts, previous studies have demonstrated that nitrogen packaging effectively preserves their sensory and textural quality. However, the effects of different sterilization intensities (F 0 =3, 5, 7, and 9) under nitrogen packaging on starch composition, microstructure, rheology, and digestibility remain unclear. To address this issue, this study was conducted. Increasing intensity reduced total starch from 50.38% to 31.90% and amylose from 17.94% to 12.76%. Rapidly digestible starch rose from 14.61% to 28.85%, while resistant starch fell from 61.88% to 36.89%. Intestinal hydrolysis rate increased from 58.93% to 73.06%, and estimated glycemic index from 53.50 to 62.30. XRD confirmed C-type crystallinity retention, but relative crystallinity was lowest at F 0 = 9. SEM revealed progressive matrix fragmentation, surface cracking, and structural integrity loss. Starch isolated from more intensely sterilized chestnuts exhibited lower storage modulus, loss modulus, and complex viscosity, indicating weakened molecular association and gel-network formation. Correlation analysis further linked the reductions in total starch, amylose, resistant starch, and viscoelastic strength with enhanced enzymatic hydrolysis and glycemic potential. These findings demonstrate that intensive sterilization facilitates starch accessibility via coordinated compositional, structural, and rheological changes, whereas milder sterilization better preserves resistant starch and low-glycemic traits.