Effect of superheated steam treatment on rice starch: study on in vitro digestibility and morphostructural, thermal and functional changes
摘要
This study evaluated the effects of superheated steam treatment (SST) on rice starch and changes in vitro digestibility, morphostructural, thermal, and functional characteristics were investigated. SST was applied at 150 °C for 3 min (SS150/3) and 5 min (SS150/5) and for the same times at 190 °C (SS190/3 and SS190/5), followed by drying and storage. SST affected the structural order, favoring gelatinization and exposing more of the double helix structure. Results indicated increased mobility of starch chains and disrupted ordered structures. The control shown a higher amount of long branches (DP ≥ 37), whereas thermally treated starches by SST exhibited a higher proportion of small amilopectin molecules, with SS190/5 being particularly noteworthy. Longer treatment times and higher temperatures caused pronounced morphological changes, including gelatinization, agglomeration, granule destruction, and surface roughness. SST also increased water and oil absorption, reduced syneresis index, and altered crystallinity. Crystallinity experienced a significant reduction for all starches subjected to SS, with SS190/5 standing out with a maximum reduction of 55.07%, as confirmed by the IR (1047/1022) cm−1. The results demonstrated the feasibility of structural and morphological modification of starch with superheated steam, mainly SS150/5 and SS190/5, obtaining properties distinct from native starch.