Emulsification Activity For The Polysaccharide Conjugates Water-extracted And Alkali-extracted From Green Tea

Tea polysaccharide is a kind of protein-binding polysaccharide conjugates extracted from tea,which has possessing various biological activities,such as anti-oxidation,hypoglycemic,enhance immunity.In this study,two tea polysaccharide conjugates?TPC?,named TPC-W and TPC-A,are obtained by water extraction and secondary alkali extraction for low-grade green tea.Otherwise,by determining the physicochemical properties of two TPC,exploring the emulsifying properties and protective abilities of emulsion stabilized by TPC on catechin,the following conclusions are drawn:1.The emulsification activities of TPC-W and TPC-A as emulsifiers and the stability of emulsion stabilized by them are studied.An oil-in-water emulsion were prepared by different concentrations?0.5 wt%,1.0 wt%,1.5 wt%,2.0 wt%,3.0 wt%?of two polysaccharides and medium chain triglyceride?MCT?and meanwhile,the mean particle diameter(d₃₂)and the zeta potential of the emulsion storage 10 days at25?were measured at interval.The results showed that the mean particle diameter?d32?of the emulsion stabilized by TPC decreased gradually with the increase of concentrations and the stability improved continuously during the storage.Especially,the emulsion stabilized by two TPC not only behaved good emulsifying properties,but also possessed well storage stability when the concentration of TPC was 2.0 wt%.2.The stability of the emulsions stabilized by TPC-W and TPC-A treated with different ionic strengths(Ca²⁺and Na⁺)and pH?2⁸?was studied.The results showed that the concentration of Na⁺?0.1⁰.5 mol/L?had little effect on the emulsion stability of the two emulsions,and the effect on the emulsion stabilized by TPC-A was lower than that on the TPC-W emulsion.When it storaged at 25°C for 10 d,the system of emulsion stabilized by TPC-A remained stable,and meanwhile,the laser confocal image also showed that the droplets were uniformly dispersed and no agglomeration occurred in emulsion system.The concentration of Ca²⁺?0.01⁰.05 mol/L?has a great influence on the stability of the two TPC emulsions.When the concentration of Ca²⁺in the two emulsion systems is lower than 0.02 mol/L,the emulsion system is relatively stable.As the Ca²⁺concentration reached 0.03 mol/L and above,the droplets in the emulsion began to aggregate and eventually appeared to be demulsified.The emulsion stabilized by tea polysaccharide showed agglomeration in the emulsion at pH 2⁴,which eventually led to the loss of stability of the emulsion.It still had good emulsifying activity and emulsion stability under the condition of pH 4⁸.