Preparation,Structural Characterization And In Vitro Bioactivity Of Selenized Mung Bean Resistant Starch

In this paper,mung bean starch was used as the test material,and mung bean resistant starch（MB-RS4）was obtained by esterification of citric acid and mung bean starch.Selenized mung bean resistant starch（MB-RS4?Se（IV））was synthesized by using nitric acid-sodium selenite method to provide coordination ions.On the basis of retaining the original biological activity of MB-RS4 endow it with new functional properties;The optimal preparation process of esterified starch and the optimal process parameters of selenization modification were determined.The yield of MB-RS4?Se（IV）and Se content were used as evaluation indicators.Optical microscopy,scanning electron microscopy（SEM）,Ultraviolet spectroscopy（UV）,Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction analysis,gel permeation chromatography（GPC）and hydrogen nuclear magnetic resonance（NMR）spectroscopy were used to determine the morphology of MB-RS4 particles before and after modification,Relative molecular mass,crystal form,functional group change and migration;To explore the in vitro antioxidant-related activity analysis of MB-RS4 before and after modification,as well as the in vitro resistance to digestion and the kinetics of the inhibitory effect onα-GA andα-AA,to explore the in vitro resistance to digestion of MB-RS4 before and after modification,Antioxidant activity and inhibitory effect on enzyme activity;the results show that:（1）The optimal process conditions for the preparation of MB-RS4 were as follows:the dry ratio of starch to citric acid was 5:2,the p H of the reaction system was 3.5,the esterification temperature was 150°C,and the esterification time was 4 h.Under these conditions,the content of MB-RS4 was 83.72%.（2）The optimal process conditions for the preparation of MB-RS4?Se（IV）were as follows:the reaction time was 3.5 h,the reaction temperature was 66°C,the volume fraction of nitric acid was 0.5%,and the selenium content of MB-RS4?Se（IV）was 2.21 when the ratio of material to liquid was 1:1.mg/g,yield 26.4506%;（3）Compared with mung bean starch granules,mung bean RS4 had more pores,appeared different degrees of cross-linking,most of the polarized crosses disappeared,and the C=O stretching vibration absorption peak appeared at 1754 cm^-1in the infrared spectrum.After selenization,the particle structure of MB-RS4 is broken,the ultraviolet spectrum is red-shifted,the crystalline region disappears,the molecular weight is significantly reduced,the configuration is inverted,and the C₆position is substituted.The characteristic absorption peaks of Se=O,C-C（Se）₂and Se-O-C appear at wavenumbers of 787.88 cm^-1,730.88 cm^-1and 654.75 cm^-1.（4）Before selenization,mung bean RS4 had antioxidant activity in vitro,and after selenization,RS4 in vitro scavenging ability of·OH,·O^2-,ABTS⁺was significantly enhanced,and increased with the increase of mass concentration;（5）Compared with mung bean starch,the in vitro anti-enzymatic properties of MB-RS4 and MB-RS4?Se（IV）were enhanced,and the digestion rate was significantly decreased;MB-RS4?Se（IV）had significant inhibitory effects onα-glucosidase andα-amylase The results of the enzymatic reaction kinetics showed that the type of inhibitory effect onα-glucosidase was competitive inhibition,and the type of inhibitory effect onα-amylase was mixed anticompetitive inhibition.