| By virtue of high shear dispersing emulsification(HSDE) technology,the extraction of four kinds of polyphenols(e.g.(-) epigallocatechin gallate,(-) epigallocatechin,(-) epicatechin gallate,and (-) gallocatechin gallate),gallic acid and caffeine in the tea leaves was studied by using 20% ethanol aqueous solution as extraction solvent.The kinetics and thermodynamics of the extraction process were investigated.The kinetic equations in extraction process of the four kinds of polyphenols,gallic acid and caffeine were obtained according to kinetic theory,and the rate constant k was also calculated.The values of thermodynamic parameters such as enthalpy,entropy and free energy were computed based on thermodynamic theory.Furthermore,the extraction mechanism was explored on the basis of kinetic and thermodynamic analyses.The optimal conditions of the extraction method through HSDE technology were as follows:extraction solution:20% alcohol aqueous solution,solid-liquid ratio:1∶50,rotation speed:10 000 r/min,extraction time:180 s,extraction temperature:313.15 K.Under the optimum conditions,the extraction efficiencies of active ingredients in tea leaves could reach up to 95%.Compared with other pretreatment methods for tea leaves,the proposed method possesses many advantages such as higher extraction speed,less consumption of extraction solution and higher extraction efficiency.The method would have a good prospect in application of the extraction of natural product. |