Regulation mechanisms and effects of thermal processing methods on starch digestibility in cornmeal staples

Current studies focus on the effect of the interaction between gluten and starch granules on starch digestibility, in a single-staple food system. However, the impact of different thermal processing methods on this interaction remains largely unexplored. This study aimed to investigate the effects of three different thermal processing methods, steaming, boiling, and baking, on the interactions between starch and non-starch components in corn flour-simulated dough and the regulatory mechanisms of action on starch digestibility. The study revealed a significant variation in starch digestibility among samples subjected to different thermal processing methods; baked samples exhibited the lowest content of rapidly digestible starch (RDS) (54.54 %); boiled samples demonstrated the highest RDS content (71.95 %), while steamed samples showed intermediate RDS contents. Multiscale analysis revealed that the primary factor responsible for these disparities was the formation of a protein network and its interaction with starch granules significantly affected starch digestibility. The low-moisture, high-temperature conditions of baking fostered a protein network stabilized by extensive hydrogen bonds and hydrophobic interactions and a high proportion of stable disulfide bond conformations. This network formed a cohesive physical barrier encapsulating starch granules and significantly impeded enzyme access. The opposite was true for samples subjected to steaming and boiling because of their high moisture environments. This study reveals the molecular mechanism by which different thermal processing methods regulate protein network stability and the structure-function relationship between protein network stability and starch digestibility.