Physicochemical Property of Starch-Soluble Dietary Fiber Conjugates and Their Resistance to Enzymatic Hydrolysis

Preparation and investigation of the resistant starch-soluble dietary fiber conjugates are very important, considering the different and meaningful physiological properties of resistant starch and soluble dietary fiber. In this study, the different starch-soluble dietary fiber conjugates were obtained by crosslinking using sodium trimetaphosphate, under the different treatments of conventional heat moisture and microwave heat moisture. The starch-soluble dietary fiber conjugates prepared under the treatment of conventional heat moisture almost completely resisted the hydrolysis of the amylolytic enzymes. However, the hydrolysis of the starch-soluble dietary fiber conjugates treated by microwave heat moisture was obvious. In the treatment of conventional heat moisture, soluble dietary fiber was combined into outer layer of the overall starch granule by the linking with 2-, 3-, or 6-OH of glucose in the amorphous region. This combination showed a large protective effect on the resistance to enzymatic hydrolysis of the whole starch granules. Whereas, in the treatment of microwave heat moisture, soluble dietary fiber was linked into the amorphous part of starch blocks derived from destructive starch granule, resulting in the conjugates with high homogeneity. Therefore, the as-prepared resistant starch-soluble dietary fiber conjugates under the treatment of conventional heat moisture have a potential to be used as new dietary supplement in the food industry.