| Tea polyphenols are a class of polyhydroxyphenol compounds that are rich in tea.It has anti-oxidation,hypoglycemic,blood pressure and other properties.This article focuses on the efficient extraction of tea polyphenols and antioxidant work.1.From the investigation of the material-liquid ratio,extraction times,extraction temperature,extraction time in the extraction process,combined with orthogonal optimization,the best extraction conditions are obtained,that is,the material-liquid ratio is 1:25 at 85?,3 times extraction of tea polyphenols,each extraction for 30 min.Under this condition,the leaching rate is 17.31%.2.According to the investigation:the the selection properties of twelve resins for tea polyphenols and conclude that DM-16X resin is the best resin.The effects of time,temperature,and pH on the static adsorption of tea polyphenols by DM-16X resin were investigated.Orthogonal software optimization was used to obtain the best static adsorption process at 25 ? for 3 h in pH 7 solution.Under this condition,the adsorption capacity of DM-16X resin is 50.58 mg/g.According to the investigation:the effect of loading speed on the dynamic adsorption of tea polyphenols by DM-16X resin,the best loading speed was 6 BV/h(1BV=10 mL resin).According to the adsorption characteristic curve,the adsorption volume of 10 mL DM-16X resin to 1.51 mg/mL tea polyphenol solution should be controlled at 12.5 BV,at which time the resin utilization rate is the largest.3.Comparing the static desorption effect of ethanol solution and self-made ternary desorption solution,the best desorption agent is 10%distilled water+90%(70%ethanol+30%eluent A).Check the time,temperature and pH the impact on desorption,combined with the optimization of response surface parameters,changed the process to eluent 30%distilled water+70%(70%ethanol+30%eluent A),temperature 55?,pH value 6,time 2 h.The elution rate measured under this condition was 93.37%.Comparing the dynamic desorption effect of ethanol solution and self-made ternary desorption solution,the best desorption agent is 10%distilled water+90%(60%ethanol+40%eluent A).It was found that when the elution rate is 6 BV/h and the volume is 80.00 mL,the dynamic elution rate can reach 91.63%.4.By establishing an adsorption thermodynamic model,it is judged that the adsorption method of DM-16X resin for tea polyphenols belongs to Langmuir adsorption.It is calculated that ?G=-2 kJ/mol<0,and the adsorption is judged to be a process.From the establishment of the adsorption kinetic model,the adsorption rate constant k=0.82 h-1,which is in line with the first-order kinetic model,indicating that the entire adsorption process of DM-16X resin for tea polyphenols is mainly controlled by the diffusion step.5.The tea polyphenol content of the obtained product measured by the ferrous tartrate method is 76.57 wt%.According to the UPLC results:EGC content is 35.94%;EC content is 4.22%,EGCG content is 18.56%,ECG content is 6.90%;final It was calculated that the content of the four catechins reached 65.62 wt%,and the content of caffeine was 16.96 wt%.The research on the antioxidant properties of tea polyphenols found that with the increase of concentration,the removal rate of DPPH free radicals and ABTS free radicals in tea polyphenol products gradually increased.The FRAP value also increased from 298.73?mol/L to 1842.36 ?mol/L,and the FRAP value of the mixture of the two components also increased,comparing the synergistic antioxidant capacity of tea polyphenols and ascorbic acid at a concentration of 0.02-0.04 mg/mL From 273.01 ?mol/L to 708.03 ?mol/L,tea polyphenol products are converted from limiting factors to promoting effects.The FRAP value of the mixture of the three also increased due to the increase in the concentration of each component.And compared with 0.1-0.3 mg/mL,the difference between the FRAP value of the three components and the mixture of the three components increased from 2916.79 ?mol/L to 3278.39 ?mol/L,indicating that the synergistic antioxidant effect is related with the concentration of each component. |
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