Effect of inulin on the pasting and retrogradation characteristics of three different crystalline starches and their interaction mechanism.

At present, there are hardly any studies about the effect of inulin (IN) on the physicochemical properties and structures of different crystalline starches. In this study, three different crystalline starches (wheat, potato, and pea starch) were compounded with natural IN, and its pasting, retrogradation, and structural characteristics were investigated. Then, the potential mechanism of interaction between IN and starch was studied. The results showed that there were some differences in the effects of IN on the three different crystalline starch. Pasting experiments showed that the addition of IN not only increased pasting viscosity but also decreased the values of setback and breakdown. For wheat starch and pea starch, IN reduced their peak viscosity from 2,515 cP, 3,035 cP to 2,131 cP and 2,793 cP, respectively. Retrogradation experiment dates demonstrated that IN delayed gelatinization of all three starches. IN could reduce the enthalpy of gelatinization and retrogradation to varying degrees and inhibit the retrogradation of starch. Among them, it had a better inhibitory effect on potato starch. The addition of IN reduced the retrogradation rate of potato starch from 38.45 to 30.14%. Fourier-transform infrared spectroscopy and interaction force experiments results showed that IN interacted with amylose through hydrogen bonding and observed the presence of electrostatic force in the complexed system. Based on the above, experimental results speculate that the mechanism of interaction between IN and three crystalline starches was the same, and the difference in physicochemical properties was mainly related to the ratio of amylose to amylopectin in different crystalline starches. These findings could enrich the theoretical system of the IN with starch compound system and provide a solid theoretical basis for further applications.

Effect of inulin on pasting, thermal, rheological properties and in vitro digestibility of pea starch gel.

The influence of inulin (IN) on pasting, thermal, rheological properties, and in vitro digestibility of pea starch gel was investigated. Results showed that as the concentration of IN in PS increased, the pasting temperature of PS gradually increased, while the value of peak viscosity, breakdown, and setback decreased. Rheological test suggested that all PS-IN gels were typical non-Newtonian fluids and exhibited a solid-like behavior. With the increased concentration of IN, hardness, chewiness, and gumminess of PS-IN gels significantly declined, in which the minimum value was at addition level of 20%. The presence of IN increased the gelatinization temperatures of PS-IN gels, while decreased the gelatinization enthalpy. Fourier-transform infrared spectroscopy (FT-IR) results indicated that no covalent bonding but intermolecular hydrogen bonding occurred between PS and IN. No influence of IN on the diffraction peak of PS after pasting was confirmed by X-ray diffraction analysis. In addition, IN decreased the content of rapidly and slowly digestible starch of PS, while increasing the content of resistant starch. These results will expand the application range of PS, and also provide a theoretical basis for the development of inulin-starch based products.

A Review of Isolation, Chemical Properties, and Bioactivities of Polysaccharides from Bletilla striata.

Recently, polysaccharides from Bletilla striata, a member of the orchidaceous family, aroused the wide interest of people, especially their isolation, chemical properties, and bioactivities. It is reported that these polysaccharides are the most important biologically active components of B. striata, exhibiting various biological activities, such as immunomodulatory, antioxidant, antifibrotic, and hemostatic effects. This review appraised the available literatures which described different aspects of B. striata polysaccharides, including the extraction, separation, purification, structural characterization, and biological activities. We expect to lay the foundation for further investigation of the application of B. striata polysaccharides in the field of functional foods and biomedicine.