Characterization Of Soybean Soluble Polysaccharide Via Esterification And Fractionation

The objective of this research was to study the octenyl succinic anhydride?OSA?modified soluble soybean polysaccharide?SSPS?formed via SSPS esterified with OSA.It was conducted to obtain a new esterified soluble soybean polysaccharide?OSA-SSPS?.Cross-flow ultrafiltration was used to separate polysaccharides after esterification process and then OSA-SSPS with high molecular weight?HM_W?as well as OSA-SSPS with low molecular weight?LM_W?were obtained.In this paper,the physicochemical properties and structural characterization of OSA-SSPS before and after the ultrafiltration were systematically determinedto explore the effect of esterification and ultrafiltration on the structure and properties of SSPS.Through the identification of structures such as FT-IR and¹H-NMR,as well as the characterization of particle size distribution,Zeta potential and viscosity,SSPS after esterification and separation were explored the changes in the structure and properties.Through the analysis the dispersion stability of the polysaccharide after esterification and separation,and exploring the ability of OSA-SSPS?HM_W?to stabilize the protein near the isoelectric point in acidic milk drinks.Then,it was analyzed the influence of the structure change of polysaccharides on its performance.Finally,the emulsifiability and stability of OSA-SSPS?HM_W?are analyzed to provide theoretical guidance for the application of OSA-SSPS?HM_W?in oil-in-water emulsion.It also clarify the influence of structural changes of OSA-SSPS?HM_W?on its properties and functions.This study aims to further deepen the research on the modification direction of SSPS.The research contents and results were listed as follows:?1?.It is showed that a new C=O stretching vibration absorption peak appeared at1730.05 cm^-1 in the FT-IR.This result indicates that the hydroxyl group of SSPS and the carboxyl group in OSA were esterified,which led to the introduction of OSA into the polysaccharide molecules to generate OSA-SSPS.Through the ¹H-NMR spectrum analysis,the characteristic peak in the hydrogen spectrum of OSA-SSPS at 0.86 ppm is the end methyl hydrogen proton in OSA.and the peak reduction?2.02 pm?of methyl hydrogen proton in the acetyl group was decreased.Due to the reaction conditions for the weakly alkaline environment,SSPS also occur in the deacetylation reaction and hydrolysis reaction when the polysaccharides in the esterification reaction.?2?.The characterization experiments after esterification showed that OSA-SSPS had larger particle size than SSPS,and the particle size distribution of OSA-SSPS?HM_W?after ultrafiltration separation was more concentrated.The particle size of SSPS less than 500 KDa is about 30 nm,the OSA-SSPS?LM_W?particle size are about 10 nm.At pH 3.8-4.6,the average particle size of OSA-SSPS?HM_W?is also greater than that of SSPS.By comparing the potential values of SSPS and OSA-SSPS?HM_W?,it is found that the absolute Zeta potential of osa-ssps is higher than that of SSPS in the range of ph2.0-7.0.This suggested that esterification modification can improve the electric charge of SSPS.Even under acidic conditions,there are still more negative charges in the molecules.Moreover,compared with OSA-SSPS?HM_W?and SSPS in low concentration,the viscosity of two polysaccharides are similar.However,with the increasing of concentration,the viscosity of OSA-SSPS?HM_W?is gradually higher than that of SSPS.These results provide theoretical guidance for the application of OSA-SSPS?HM_W?in industry.?3?.The dispersion stability and morphological analysis of acid milk drink showed that,OSA-SSPS?HM_W?had better stability in acid milk drink than SSPS.Compared the stability of SSPS with OSA-SSPS?HM_W?in the acidic milk drink?AMD?,the measurement of dispersion state?e.g.precipitation percent and turbidity?after centrifugation confirmed that OSA-SSPS?HM_W?stabilized protein better than SSPS?t-test,p<0.05?.Within the range of0.2-0.5%polysaccharide content,the particle size of acidic milk beverage stabilized by OSA-SSPS?HM_W?is smaller than that stabilized by SSPS,and the Zeta value is also higher.It indicates that the OSA-SSPS?HM_W?can provide more steric hindrance and electrostatic repulsion,so that the protein near the isoelectric point can be stably dispersed in the system.?4?.Emulsion activity and emulsion stability of OSA-SSPS?HM_W?were superior to OSA-Starch and SSPS.The characterization of the nano-emulsion emulsified by OSA-SSPS?HM_W?or SSPS as emulsifiers showed that the particle size of the nanoemulsion of OSA-SSPS?HM_W?was between 200-300nm,while the particle size of the nanoemulsion prepared by SSPS was larger.Moreover,at the addition of 2%SSPS,oil-water separation will occur in the emulsion during the storage.OSA-SSPS?HM_W?also has better emulsification and stability even at low concentrations.This is related to the introduction of hydrophobic groups in the esterification process.The introduction of OSA enhances the amphiphilicity of polysaccharides and improves their emulsification performance,while the large particle size and increased charge of polysaccharides also improve the emulsification stability of OSA-SSPS?HM_W?.