Physicochemical Properties And Emulsifying Activity Of Polysaccharide Conjugates Prepared From Chin-brick Tea

Tea polysaccharide conjugates?TPC?is a glycoconjugate in which proteins are bounded with the polysaccharide chin.It has been reported that they have showed various bioactivities,such as antioxidant,hypoglycemic and immunological activities,and so on.In this study,the hot water extraction process of polysaccharides from Chin-brick tea was optimized by using single-factor and response surface Box-Behnken experiments.And its basic physical and chemical properties were also characterized.Further more,the emulsifying activity and emulsifying stability of TPC used as food emulsifiers were studied by measuring particle size distribution,mean particle size,Zeta-potential,and confocal scanning fluorescent laser microscopy.The results were as follows:1.The optimum extraction process of the TPC of the chin-brick tea was extraction temperature 95?,,extracting time 3.3 h,liquid-raw ratio 1:16?g/mL?,under optimum extraction conditios,the extraction yield of TPC was 10.89%.The molecular weight of the extracted TPC was 31580 Da,and 15 kinds of amino acids were measured in the TPC.Through the FT-IR,UV and Coomassie brilliant blue dye method,it was inferred that the protein contained in the tea polysaccharide is a covalently bound protein,and the protein is surrounded by the surrounding sugar chains,thereby shielding many characteristics of its protein part.The major monosaccharide components in the TPC of the chin-brick tea are arabinose,rhamnose,galactose,glucose,xylose,mannose,and galacturonic acid.2.The emulsifying activity and emulsifying stability of TPC as emulsifiers were studied.The ability of TPC to act as emulsifiers at the same concentration is superior to acacia gum?GA?in reducing interfacial tension.With the increase of the concentration of TPC,the size of the droplets forming the emulsion gradually decreased and the storage stability increased.When the TPC concentration was 2%,the emulsion had both good emulsification activity and good storage stability.Different concentrations of TPC emulsions exhibited pseudoplastic behavior,that is,as the shear rate increased,the viscosity of the emulsion decreased,but the viscosity did not directly affect the stability of the emulsion.3.The thermal stability,pH stability and ionic strength stability of TPC emulsions were studied.The results showed that the TPC emulsions still has stable emulsifying activity and emulsion stability under heat treatment?70-90??and different pH?2-8?.The concentration of Na⁺?0.1-0.5 mol/L?has no effect on the emulsion stability of the emulsion.When stored at 60?for 10 days,the emulsion system remains stable,and the laser confocal images also show that the droplets are uniformly dispersed throughout the emulsion system without polymerization.Ca²⁺concentration?0.01-0.05mol/L?has a great influence on the stability of the emulsion.When the Ca²⁺concentration in the emulsion system is 0.01-0.02 mol/L,the emulsion system is relatively stable,with Ca²⁺concentration increasing to 0.03 mol/L.At or above the concentration,the entire emulsion system loses its stability,and laser confocal images show that there is a large coalescence of oil droplets in the emulsion.The appearance of the emulsion shows that the emulsion forms a similar“gel state”.