Rheological Properties, Molecular Distribution, and Microstructure of Fortunella margarita (Lour.) Swingle Polysaccharides

Fortunella margarita polysaccharides (FMPS) are one of the main bioactive components of F. margarita. The activity is related to their rheological properties and structure. The objective of this study was to investigate the relationship between rheological properties, molecular distribution, and microstructure of crude FMPS (C-FMPS) and purified FMPS (P-FMPS). The results showed that both of solutions were shear-thinning pseudoplastic fluids with flow properties in line with the Power Law model. The pseudoplasticity of P-FMPS was stronger compared to C-FMPS. Additionally, the molecular weight and polydispersity of P-FMPS were greater, whereas the molecular radius was less compared to C-FMPS. The surface of C-FMPS was rough and dense whereas P-FMPS displayed a smooth network structure by environment scanning electron microscopy. According to confocal laser scanning microscopy, C-FMPS dispersed in the medium without connected network, whereas the network of P-FMPS was unevenly distributed in the medium and the shape was compact and smooth. The molecular distribution and microstructure of P-FMPS were attributed to the purification process while rearrangement and aggregation of polysaccharide molecules took place, which resulted in the significant difference of rheological properties between C-FMPS and P-FMPS. Practical Application The rheological properties, molecular distribution, and microstructure of F. margarita polysaccharides were first time investigated in this study. The results provided background and practical knowledge for the effective preparation, purification of FMPS, and demonstrated the relationship between the structure and rheological properties. FMPS could be explored as a natural food thickener, stabilizer, and texture modifier due to its specific rheological properties.