A novel source of resistant starch from ginger (Zingiber officinale Roscoe): Structural characteristics and bile acid...

A comparative study was conducted to investigate the structural properties and bile acid binding capacity in vitro of type II, III, and IV ginger-resistant starches. The results demonstrated that both ginger resistant starch types II (GRS2) and IV (GRS4) exhibited a similar granular morphology to the original starch, manifesting as an elliptical, flaky structure. Ginger resistant starch type III (GRS3) displayed a dense, ravine-like rough structure. The relative molecular weight of GRS2 (3.485 × 10⁶ g/mol) was greater than those of GRS3 and GRS4. This finding indicated that the molecular weight of resistant starch was reduced by physical and chemical modification, respectively. GRS4 exhibited the lowest crystallinity (49.91 %), indicating that citric acid modification reduced the crystallinity of ginger starch and destroyed the degree of ordering of the starch molecules. Following the implementation of physical modifications, the ordered structures (long-range and short-range ordered structure) of GRS3 exhibited an increase. GRS2 and GRS4 contained a negligible amount of free water, while GRS3 contained a small amount of weakly bound water. GRS3 exhibited the highest degree of branching, whereas GRS4 showed the lowest. Furthermore, among these samples, GRS3 exhibited the most robust in vitro bile acid binding capacity (37.37 %), which was associated with the granular characteristics and the degree of ordered structure of ginger resistant starch.