Multiscale Structural Disorganization of Indica Rice Starch under Microwave Treatment with High Water Contents

While the cooking of rice into porridge or similar foods is widely practiced, how microwave treatment, a rapid heating technology, changes the structure of rice starch with excess water remains largely unexplored. This work describes the multiscale structural changes of indica rice starch (IRS) with high water contents (70, 80, and 90 wt %, wet basis) subjected to microwave treatment for 1-3 min. Microwave treatment destructed crystalline lamellae, changed the crystalline type from A to B+V, and decreased crystallinity and double-helix content. While these changes depend on both water content and treatment time, the former had a stronger effect due to combined effects of water and heat for starch gelatinization. Interestingly, a highly porous material can be obtained simply upon microwave treatment of IRS for 3 min at a water content of 90 wt %. Thus, this work presents a simple method for creating such material promising for encapsulation and delivery applications.