Structural characteristics and prebiotic effects of Semen coicis resistant starches (type 3) prepared by different methods

In order to investigate the effects of different preparation methods on Semen coicis resistant starch, the structural properties and prebiotic effects of autoclaving treatment-purified S. coicis resistant starch (GP-SRS3), ultrasonic-autoclaving treatment-purified S. coicis resistant starch (UP-SRS3), enzyme-autoclaving treatment-purified S. coicis resistant starch (EP-SRS3) and microwave-moisture treatment-purified S. coicis resistant starch (MP-SRS3) were studied compared to high-amylose maize starch (HAMS). Fourier transform infrared spectroscopy and Solid-state 13C NMR spectroscopy showed all of SRS3 displayed B-type crystallite structure, furthermore, MP-SRS3 and UP-SRS3 showed higher degree of ordered structure and degree of double helical structure compared to other samples. Field emission scanning electron microscopy showed MP-SRS3 displayed deeply layered strips and UP-SRS3 exhibited some cavities. Moreover, S. coicis resistant starch could promote the growth of Bifidobacteria adolescentis better compared to high-amylose maize starch, among these samples. MP-SRS3 exhibited best prebiotic effect, which was possible attributed to its rough surface and double helix structure. B. adolescentis displayed a higher survival rate to the simulated gastrointestinal tract environment in SRS3 medium than that in high-amylose maize starch medium, especially MP-SRS3 and UP-SRS3, which partly contributed to its strips and cavities. Overall, MP-SRS3 could be regarded as a potential prebiotic to promote the growth of B. adolescentis for its structural trait.