The Antioxidant Activity And Rheological Property Of Modified Polysaccharides From Ulva Fasciata

Ulva fasciata is a kind of medicinal and edible seaweed,which has a high nutritional value and pharmacological effect.Most of the study is focused on its structure,extraction,isolation,purification and biological activity,the study about modified polysaccharide is ignored.To expand the apply of Ulva fasciata polysaccharide on the field of functional food,this paper choosed 10-30K Ulva fasciata polysaccharide as raw material,which has relatively good antioxidant activity.First,pectase was choosed as the right hydrolase through sieve enzyme experiment,then the enzymatic hydrolysis condition of polysaccharide from Ulva fasciata were optimized by single factor experiment and orthogonal design.The optimal extraction conditions obtained by orthogonal design were as follows:reaction temperature 55,reaction pH 4.5,concentration of enzyme solution 7.5%and reaction time5h.The effect of single factor in the order was temperature,time,pH and concentration.The Ulva fascita polysaccharide before and after enzymatic degradation were evaluated on their antioxidant activity in vitro systems.The result showed that Uf5 showed the best scavenging effect on·OH?DPPH·and reducing power;Uf5's·OH and DPPH·removal rate reached 51.5%and 29.31%,while its concentration was 2.5mg/mL.The reducing power was also not significantly improved after enzymatic degradation.The spectral characteristics and antioxidant capacity of polysaccharide-gelatin peptide maillard product in different pH,temperature,time and ratio were analyzed.The result showed that the maillard brown products and intermediate products increased with the increase of pH,polysaccharides concentration,temperature and time.pH and free amino groups decreased with the increase of temperature and time;the antioxidant activity of maillard products increased with the increase of temperature,time and pH.UG-100's removal rate of·OH reached 57.68%after 3h reaction.The DPPH·scavenging ability and reducing power of UG-1:1 was better than that of UG-2:1 and UG-1:2,its removal rate was 58.74%;and its reducing power was 0.295,when the pH was 10;the O^2-·scavenging ability of UG-2:1 was better than that of UG-1:1,UG-1:2.Through the study of pH,polysaccharides concentration,Ca²⁺concentration,Na⁺concentration and temperature's effect on the rheological properties of maillard products,the result showed temperature had the greatest influence on viscosity,the change value reached0.74mPa·s,other factors according to the size of effect as follows:pH,Ca²⁺,Na⁺,polysaccharides concentration.pH had the greatest influence on the properties of the fluid.During pH1-5,maillard sample showed shear thinning non Newtonian properties.During pH7-12,showing a similar Newtonian fluid properties.While other factors didn`t change the fluid properties significantly.