Structural characteristics and crystalline properties of lotus seed resistant starch and its prebiotic effects

Lotus seed resistant starch (LRS) is a type of retrograded starch that is commonly known as resistant starch type 3 (RS3). The structural and crystalline properties of unpurified LRS (NP-LRS3), enzyme purified LRS after drying (GP-LRS3), and enzyme purified LRS (ZP-LRS3) were characterized. The result showed that the molecular weights of NP-LRS3, GP-LRS3, and ZP-LRS3 were 0.102 × 106, 0.014 × 106, and 0.025 × 106 Da, respectively. Compared with native starch and high amylose maize starch (HAMS), LRS lacked the polarization cross and the irregularly shaped LRS granules had a rougher surface, B-type crystal structure, and greater level of molecular order. The FT-IR measurements indicated no differences in the chemical groups. Analysis by 13C NMR indicated an increased propensity for double helix formation and higher crystallinity in LRS than in the two other types of starch. Moreover, LRS was more effective than either glucose or HAMS in promoting the proliferation of bifidobacteria.