Effects of Alpinia oxyphylla fructus polysaccharide on the gelatinization, retrogradation, structural characteristics, antioxidant activity, and in vitro digestibility of corn starch

Alpinia oxyphylla fructus polysaccharide (AOFP) exhibits diverse biological activities, but its influence on starch properties remains underexplored. This study elucidates the effects of AOFP on the gelatinization, retrogradation behavior, and functional characteristics of corn starch (CS). Iodine binding capacity, XRD, and FTIR analyses revealed that AOFP significantly inhibited amylose leaching, likely through hydrogen bonding interactions, thereby suppressing starch recrystallization and retrogradation. At a 6 % AOFP concentration, the relative crystallinity of the system decreased from 14.910 ± 0.320 % to 6.023 ± 0.142 % on Day 7, the retrogradation rate (R₇) declined from 54.95 ± 1.07 % to 32.58 ± 1.08 %, and the gel hardness was reduced from 187.32 ± 1.87 gf to 66.06 ± 1.08 gf. Additionally, AOFP significantly increased the resistant starch (RS) content from 10.96 ± 0.38 % to 19.08 ± 1.06 % and enhanced the antioxidant capacity of the composite system, with ABTS⁺ and DPPH radical scavenging activities increasing by 88.59 ± 1.1526 % and 76.24 ± 1.3277 %, respectively. These findings collectively demonstrate that AOFP is a functional ingredient capable of modulating both structural and functional properties of starch-based foods.