The Study On Extraction And Properties Of Pectin From Soybean Hull

Soybean hull as major co-product of the soybean processing industry hasn’t been utilized fullydue to its special component and structure. The research on extraction and properties of soybeanhull pectin could provide theoretical basis for soybean hull application and improve the added valueof soybean hull.The comparison of different extraction and purification methods on the production of soybeanhull pectin （SHP） was studied. There extraction methods including hydrochloric acid heated bywater bath （WH）, ammonium oxalate heated by water bath （WO） and ammonium oxalate heated byhigh pressure steam （HO） were investigated by comparing the yields and purities. The resultsindicated that the yield of HO （9.21%） and WH （8.71%） were higher than WO （7.13%）, the purityof WH （37.25%） was lower than WO （56.28%） and HO （56.59%）, but HO extraction time was just20min, so HO was the best extraction method. The optimal conditions were as follow: the ratio ofmaterial and liquid was1:20, the extracting temperature was125℃, the extracting time was20min,the concentration of ammonium oxalate was0.6%. Comparison the different purification methodsincluding dialysis, washed by alcohol and ultrafiltration illustrated that ultrafiltration was mosteffective to purified SHP. The purities of SHP purified by50kDa and100kDa ultrafiltration were71.69%and74.99%. The SHP recovery by50kDa and100kDa were85.05%and80.25%. Theyields by50kDa and100kDa were9.53%and9.12%. Considering the recovery, yield and purity,50kDa ultrafiltration was chose as the purification method.The physicochemical properties of SHP were studied. The results were as follow: the totalgalacturonic acid was71.28%, ash was1.87%, acid insoluble ash was0.58%, lose on drying was6.9%, protein was4.74%, the degree of esterification was53.19%. SHP had the characteristicabsorption peak of pectin at1630¹650cm-1and1740¹760cm-1during FTIR test. The Molecularweight of SHP and Commercial pectin were4.914×105Da and3.777×105Da. The study ofmonosaccharide composition illustrated that SHP was rich in galacturonic acid. The main neutralsugars of SHP were mannose, rhamnose, glucose and galactose.The rheological properties and emulsion stabilizing properties of SHP were discussed. Theresults showed that the viscosity of SHP was increased as the raise of concentration of pectin andCa²⁺. The viscosity of SHP was decreased as the raise of temperature and shear rate. The viscosityof SHP was highest when pH was3.0-5.0. The emulsion stabilizing properties test illustrated thatthe emulsion particle size of SHP was decreased as the raise of pectin concentration. The emulsionparticle size of SHP was increased as the raise of Ca²⁺concentration. The emulsion particle size ofSHP was smallest when pH was5.0. After7d storage at37℃, the particle size of4%Commercialpectin and10%Arabic gum increased from5.63μm and5.84μm to6.41μm and6.56μm, but theparticle size of4%SHP increased from8.30μm to11.72μm.The modification procedure was conducted as follow: SHP and water were mixed and the ratioof SHP and water was20:80. After12h storage at75℃, the solution was freezed drying. Themodification procedure conjugated protein and polysaccharide and the hydrophobicity of SHP wasimproved. The results illustrated that the Molecular weight of modified SHP （1.182×106Da） wasimproved. After7d storage at37℃, the emulsion particle size of4%modified SHP increased from5.60μm to6.69μm. The pectin adsorption ratios of4%Commercial pectin,4%unmodifiedSHP and4%modified SHP were40.52%,42.42%and58.05%. The viscosities of10%Arabic gum,4%Commercial pectin,4%unmodified SHP and4%modified SHP were11.907mPa s,69.783mPa s,13.960mPa s and15.850mPa s.