Asymmetrical flow field-flow fractionation combined with liquid chromatography enables rapid, quantitative, and structurally informative detection of resistant starch

• A quantitative and structurally informative detection method for resistant starch. • Field-flow fractionation provided structural information of resistant starch. • Structure characterization and content of RS were studied over entire molar mass. • Amylose molecules from C-type starch had significant resistance to digestion. Resistant starch (RS) is one kind of biomacromolecules with prebiotic effects. Nowadays, it is still a challenge to characterize structure and content of RS over entire molecular weight ( M w ) distribution. In this study, a combined technique of asymmetrical flow field-flow fractionation (AF4) and liquid chromatography (LC) for the accurate structure characterization and quantitative analysis of RS was developed. AF4 coupled online with multiangle light scatting (MALS) and differential refractive index (dRI) detectors (AF4-MALS-dRI) was used to characterize the structural information (radius of gyration and M w ) and content of RS with M w larger than 5 kDa. Meanwhile, RS was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The glucose content in the digested starch solution was quantitatively determined using LC. The results demonstrated that AF4-LC is a simple and rapid method for structurally informative detection and quantitative analysis of RS over entire M w distribution.