Study On The Extraction-purificationa And Some Propeties Of Polysaccharide Extrated From Gracilaria Greville

Previous studies found that the biological activities of polysaccharide are related to its content of sulfated groups.Gracialaria Greville contains high sulfate groups with multiple biological activities.In order to have an o verall study of Gracialaria Greville and explore its possible application for intensive processing,the present study extracted polysaccharides from Gracialaria Greville assisted with celluase,and the optimal condition was obtained through well fitted models;Deproteinization technique for crude polysaccharides from Gracialaria Greville was investigated and optimized,and purified Gracialaria Greville polysaccharides(GSPS)were obtained;Using agar(sold in market)as a reference,the antioxidant activity and rheological characteristics of GSPS were studied and compared.The main conclusions were as follows:1.Based on single-factor experiment results,the effects of different particle sizes,enzyme addition amo unts,temperatures,materia to liquid ratio s on GSPS extraction were studied and the data were fitted into three empirical models.The results showed that the optim1m model was Ct=C∞(1-e-kt-b).Compared with same extraction condition with water,the activation energywas decreased by 54.6%with cellulose assisted.2.Single-factor experiments showed that the deproteinization rate of GSPS was influenced by enzyme addition amount,enzymolysis temperature and time.Box-Behnken design was used to optimize the deproteinization process of GSPS.The optimal parameters were obtained as:enzyme addition of 149 U/mL,enzymo lysis temperature of 57 ℃,and time of 1.5 h.Under these parameters,the deproteinization rate was 80.05%.UV-Spectrum scan in 220-400 nm indicated that protein is nearly moved.3.Starch,amino acid,reducing sugar and phenols were not found in agar and GSPS.Compared with agar,GSPS had a lower content of polysaccharide and 3,6-anhydro-galactose,but contents of protein and sulfated group were much higher.The antioxidant activity of GSPS and agar in vitro had a certain linear relationship with their concentrations.Except for H2O2 scavenging activity,GSPS showed higher activities than agar in ·OH,·DPPH scavenging activities,and lipid peroxide inhibition ability of GSPS at high concentrations was equaled to Victim C.4.GSPS and agar solution of 8.0 mg/mL were pseudoplastic fluid with distinct characteristic of shear thinning at 75℃.The viscoity and thixotropy of GSPS both were lower than agar under the same concentration and temperature.The storage modulus(G’)of GSPS was lower than loss modulus(G")at high or low frequency,indicating that the solution system was under collosol condition.On the contrary,the loss modulus(G")of agar changed to be higher than the storage modulus(G’)when the angular frequency increased to 3 rad/s,which indicated that the solution system was under gel condition.The tenperature of melting and freezing of GSPS both were lower than agar(melting temperature:GSPS 37 ℃,agar 91℃;freezing temperature:GSPS 10℃,agar 37℃),which means it could be used as a thickener for chilled foods.It was found that pH changing did not alter the fluid type of GSPS.However,the viscosity of solution system significantly decreased but thixotropy increased when pH of GSPS solution(pH=6.0)was adjusted to 3.0.But no significant influence on its viscosity and thixotropy was observed when GSPS pH was adjusted to 9.0.In addition,the additions ofNaCl,CaCl2 and sucrose did not alter fluid type of GSPS solution,but the viscoity and thixotropy of GSPS decreased with the increase ofNaCl,CaCl2 and sucrose concentrations.