Structural Characterization Of Jujube Polysaccharides From Subcritical Water And The Stability Of Jujube Juice

In this paper,subcritical water was used to extract crude polysaccharides from jujube,and the influencing factors and main components were analyzed.The crude polysaccharides extracted from subcritical water at 130℃ were fractionated by cellulose column,and the oxidation stability of the separated components was studied.The stability of jujube juice was also discussed.The main contents are as follows:In the first part of this paper,the extraction of crude polysaccharides from jujube was studied.The results showed that the crude polysaccharide yield was relatively higher at the temperature of 140℃ and the ratio of solid to liquid 1:20 than others.Sugar analysis showed that jujube crude polysaccharides mainly contain glucose and arabinose,in addition to galactose and galacturonic acid,a small amount of xylose and mannose.The apparent structure of jujube residue obtained at different temperatures was not significantly different by electron scanning microscopy.In the second part,crude polysaccharides extracted from subcritical water at 130℃ were decolored by AB-8,deproteinized by Sevag reagent,dialyzed by flow water and lyophilized.Neutral polysaccharide(JDPN)and acidic polysaccharides(JDP1,JDP2 and JDP3)were obtained by fractional separation of DEAE-52 cellulose column.The isolated jujube polysaccharides were characterized by UV,IR,sugar analysis,thermal stability analysis,molecular weight determination,methylation and apparent structure observation,and so on.JDPN was mainly composed of glucose(43.35%),galactose(26.35%)and arabinose(24.47%),and a small amount of mannose.JDP2 is mainly composed of galacturonic acid(40.5%)and glucose(30.4%),in addition to arabinose,rhamnose,galactose and a small amount of mannose;JDP3 mainly composed of galacturonic acid(97.56%)and a small amount of galactose.It was found that the thermal stability of JDPN was the worst,and the thermal stability of JDP1 and JDP2 was similar,the thermal stability of JDP3 was relatively good.JDPN composition is not uniform,containing 9807 Da and 3409 Da two relative molecular weight,acid polysaccharide composition is relatively uniform,JDP1 is 3689 Da,JDP2 is 3313 Da,and JDP3 is 3242 Da.The results of methylation of JDP2 show that the glycosidic bonds are mainly composed of 1,4-D-galacturonic acid(31.27%)and 1,4-D-glucopyranose(29.73%),in addition to 1,3-L-rhamnose,terminal furan arabinose and 1,3,4-L-pyran arabinose.The surface of the two types of polysaccharides are smooth,with hollow beads and stripes,but their morphology is slightly different.The oxidative stability of jujube polysaccharides isolated from cellulose column was studied.It was found that some jujube polysaccharides had certain ability to remove superoxide anion,hydroxyl radical and DPPH,and had certain reducing power.Finally,the stability of jujube juice extracted from subcritical water was explored.It was found that the addition of different concentrations of sucrose,citric acid and salt had some influence on the stability of jujube juice.When 5% sucrose was added,the value and stability coefficient are favorable,more conducive to the stability of-20℃ low temperature preservation of jujube juice.