| In this paper,jujube(’Jinsixiaozao’)and wild jujube(from Zanhuang county)as material were studied the properties and activities of the carboxymethylated polysaccharides products.This research will provide guidance for the scientific development and utilization of jujube polysaccharides.The main research results are as follows:1.The polysaccharides of wild jujube and ’jinsixiaozao’ were isolated by water extraction-alcohol precipitation,purified by Sevage method to remove the free protein and modified by carboxymethylation.The carboxymethylation condition was optimized by response surface method.The optimal process conditions for wild jujube polysaccharide carboxymethylation were reaction temperature:80℃,addition of monochloroacetic acid:3%,NaOH concentration:2.5 mol/L which caused the highest substitution degree,0.76.The optimum process conditions for polysaccharide carboxymethylation of Jinsixiaozao were reaction temperature:60℃,addition of monochloroacetic acid:2%,concentration of NaOH:2.5 mol/L,and the degree of substitution was 0.24.2.Properties of the polysaccharides and modified were compared by determination of solubility,viscosity and molecular weight,monosaccharide composition analysis,UV scanning,infrared spectroscopy analysis and scanning electron microscopy observation.(1)Wild JujubeCompared with unmodified wild jujube polysaccharide,water solubility and viscosity were improved in polysaccharide carboxymethylation.The water solubility of the modified and un-modified particles were 48.63±1.23 mg/mL and 86.73±0.72 mg/mL respectively;the viscosity 2698±99.8 mPa.s and 2430.4±95.65 mPa.s respectively.Chemical analysis revealed that wild jujube crude polysaccharide was composed of Rha:Ara:Xyl:Man:Glc:Gal-0.60:1 0.13:0.80:0.32:0.37:2.29 with a molecular weight of 297636 Da,Chemical analysis revealed that polysaccharide carboxymethylation was composed of Rha:Ara:Xyl:Man:Glc:Gal=2.27:56.57:4.42:5.31:1.67:12.45 with a molecular weight of 317120 Da.The results of infrared spectroscopy was capable of proving that CH2COOH was successfully led into jujube polysaccharide by the observation of enhanced vibration absorption COO-.Scanning electron microscopy exhibited that carboxymethylated wild jujube polysaccharides were stacked in flakes,the surface was smooth and the bonding of the polysaccharides was loose.Energy spectrum analysis showed that the proportion of O was increased and Na was led into.(2)JujubeThe carboxymethylation also increased the solubility of ’Jinsixiaozao’ polysaccharide and decreased its viscosity.The water solubility of the modified and un-modified particles were 50.8±0.93 mg/mL and 85.1±1.27 mg/mL,respectively,and the viscosity 2701.5±100.1 mPa.s and 2628.5±90.2 mPa.s,respectively.Chemical analysis revealed that ’Jinsixiaozao’ polysaccharide was composed of Rha:Ara:Xyl:Man:Glc:Gal=0.31:7.69:0.54:0.15:1.08:1 with a molecular weight of 274727 Da,Chemical analysis revealed that polysaccharide carboxymethylation was composed of Rha:Ara:Xyl:Glc:Gal=0.18:9.09:0.45:0.36:1 with a molecular weight of 303910 Da.The infrared spectrum results of’Jinsixiaozao’ polysaccharide showed that CH2COOH was introduced after carboxymethylation.The scanning electron microscope results of ’Jinsixiaozao’ showed that its carboxy methylated polysaccharide had a dense structure with different surface levels and spherical particles.The proportion of O was increased in the energy spectrum,and the Na was introduced.3.The activity of carboxymethylated jujube polysaccharide was also studied.The results showed that carboxymethylated polysaccharide exhibited certain antioxidant activity which stronger with the increase of polysaccharide concentration.Carboxymethylation was not capable of improving the reducing ability of jujube polysaccharide,yet it significantly improved the scavenging ability to hydroxyl radicals.At a concentration of 5 mg/ml,the scavenging rate was 95.8±1.06%,whereas only 82.8±0.78%for crude polysaccharide.For carboxymethylated‘Jinsixiaozao’polysaccharide,the ability of scavenging 1,1-diphenyl-2-picrylhydrazyl(DPPH)and hydroxyl free radicals was evidently improved.The DPPH scavenging rates before and after carboxymethylation were 86.02±0.85%and 90.47±0.04%at 5 mg/ml carboxymethylated‘Jinsixiaozao’polysaccharide,and the scavenging rates to hydroxyl radicals were 37.34±0.68%and 79.44±1.06%,respectively.The reduction ability of‘Jinsixiaozao’crude polysaccharide and carboxymethylated polysaccharide were similarly weak.4.The prebiotic activity of jujube and wild jujube polysaccharides were also studied.The results showed that carboxymethylated wild jujube polysaccharide had better growth-promoting effects on Lactobacillus Acidophilus and Lactobacillus Rhamnosus,and the growth-promoting effect was positively correlated with polysaccharide concentration.In addtion,carboxymethylated ’Jinsixiaozao’ polysaccharide significantly improved the growth of probiotics at all the tested concentrations of 0.5%,1%,1.5%. |
PDF Full Text Request