Structural Analysis And In Vitro Inhibitory Effect On ?-glucosidase Activity Of Dietary Fiber Of Millet Bran

The purpose of this paper is to investigate the modifiecation methods,structural characteristics and in vitro inhibitory effect on ?-glucosidase activity of water soluble dietary fiber of millet bran.In order to increase the yield of water soluble dietary fiber of millet bran,the method of ultrasonic cooperated with microwave and enzyme were used to modify the dietary fiber of red valley millet bran which was pre-processed by the method of steam explosion.Also,the process conditions of water soluble dietary fiber of millet bran was optimized by response surface methodology.After that,the structures of the unmodified and modified dietary fiber of millet bran were investigated with the scanning electron microscopic,gel permeation chromatography-refractive index-multi-angle light scattering(GPC-RI-MALS),X-ray diffraction,infrared spectroscopy and ion chromatography.The in vitro model of inhibitor of ?-glucosidase was created to explore the inhibitory effect of original water soluble dietary fiber of millet bran and modified water soluble dietary fiber of millet bran on ?-glucosidase activity.Results are listed as follows:(1)The steam exploration condition is set as pressure of 1.0 MPa and time of 90 s,under which the content of water soluble dietary fiber is as high as 10.841% with the optimal process parameters: microwave power is 535 W,material-to-liquid ratio is 1:50 g/mL and the synergistic time of the ultrasonic-microwave is 57 min.For the method of enzyme,the content of water soluble dietary fiber is 10.507% with the optimal process parameters: enzyme dosage is 5.94%,temperature is 56 ?,pH value is 4.65 and time is 3 h.(2)Scanning electron microscopic observation demonstrates that the surface of modified water soluble dietary fiber of millet bran becomes rough,loose and porous and it is assembled by small particles.GPC-RI-MALS indicates that both the original water soluble dietary fiber of millet bran and the modified one have a wide molecular weight distribution.According to the idea of average molecular weight,the molecular weight of modified water soluble dietary fiber of millet bran is considered to be smaller.The X-ray diffraction analysis illustrates that the crystallinity of the modified insoluble dietary fiber increases,meaning that the non-crystalline region in the modified insoluble dietary fiber of the millet bran partially degrades and converts to water soluble dietary fiber.The infrared spectroscopic analysis demonstrates that there are no significant changes in the chemical functional groups between the modified water soluble dietary fiber and insoluble dietary fiber of millet bran,and both of them possessed the characteristic absorption peaks of carbohydrates.The result of ion chromatogram shows that both the original water soluble dietary fiber and modified water soluble dietary fiber of millet bran consist of arabia,galactose,glucose,xylose,mannose and fructose yet with different contents.(3)Based on the test of inhibitory effect on ?-glucosidase activity of water soluble dietary fiber,the inhibitory curve equation of original water soluble dietary fiber of millet bran can be concluded as:y=26.36499×ln(x+15.62773),R2=0.90282.Its half-maximal inhibitory concentration(IC50)value is 2.934 mg/mL.The inhibitory curve equation of modified water soluble dietary fiber of millet bran is: y=61.70976×ln(x+3.61844),R2=0.91352.Its IC50 value is 0.423 mg/mL.In conclusion,the method of ultrasonic cooperated with microwave is more suitable for the the modification of millet bran dietary fiber with respect to the method of enzyme.The structures of millet bran dietary fiber before and after modification are analyzed in this paper.The ultra-structure,molecular weight distribution,crystal type,chemical functional group composition,monosaccharide composition and content of millet bran dietary fiber are determined.The structures of millet bran dietary fiber before and after modification are compared and analyzed.Based on in vitro test,both of original water soluble dietary fiber and modified water soluble dietary fiber of millet bran possess the inhibitory effect on the activity of ?-glucosidae.The inhibitory effect on ?-glucosidase activity of modified water soluble dietary fiber of millet bran is stronger than that of original water soluble dietary fiber of millet bran.