| Recent years,Ginkgo biloba health tea has been wildly developed.However,there was no uniform production and testing standard of Ginkgo biloba health tea in China.Hence,this work systematically studied the preparation technology of Ginkgo biloba tea which influences its health substances,toxicity and flavor substance content.Furthermore,its detection and evaluation methods has discussed in detail.All of these works were conducted on the basis of exploring the methods for detecting biological activities in Ginkgo biloba tea.(1)HPLC method was used to determine the content of flavonoids,terpene lactones,ginkgolic acids,caffeine,five catechin monomers and gallic acid.Moreover,the phenol-sulfuric acid method was applied to measure the polysaccharide determination.The content of amino acid and cyanide content was investigated by ninhydrin colorimetry and fluorescence spectrophotometry,respectively.In order to avoid the interference of flavonoids in the determination of tannins,dual chromophoric systems was adopted in present work.The test result suggested that the standard deviation of tannin content was varied from 0.24 to 0.62 mg/g and the recovery was range from 101.8 to 108.0%.(2)The effects of the preparation technology of Ginkgo biloba tea on the content of flavonoids,terpene lactones,tannins and polysaccharides were studied.The results showed that the fixation time,temperature,rolling time and drying conditions had different effects on the health and flavor content of Ginkgo biloba tea.Under the optimal condition(steam fixation(100°C)for 2.5 min,rolling for 5 min,and drying at 60°C for 4 h),Ginkgo biloba tea can retain the highest health substances content.Moreover,the highest content of health substances in tea infusion was found when the first brewing(100°C)at 15 min.(3)The Chinese tea national standard was adopted to test the flavonoids catechins,gallic acid and amino acids of Ginkgo biloba tea.The effects of Ginkgo biloba tea's preparation technology on catechin,gallic acid and amino acid content were investigated.The phenol-ammonia ratio was further calculated.The results showed that the phenol-ammonia ratio in the tea infusion was the lowest under steam-fixing conditions.The content of flavor substances in Ginkgo biloba tea was the highest when rolled for 5 min and dried at 60? for 4 to 6 h.The flavor of tea was the best,when the tea was first brewed at 80? for 15 min.(4)The toxicity of Ginkgo biloba tea and its influencing factors were discussed.The results showed that ginkgolic acids content decreased with the increaseing fixation temperature and drying time.However,the ginkgolic acids content in tea infusion increased with prolonged rolling time.Under the optimized process,10.34 mg/g of ginkgolic acids in Ginkgo biloba tea and 2.8 mg/L of ginkgolic acids content(? 5 ppm)in tea infusion can be detected.The fluorescence spectrophotometric method was used to detect cyanide in Ginkgo biloba leaves and Ginkgo biloba tea,the content was lower than the detection limit(0.002 mg/L).(5)The best preparation process of Ginkgo biloba tea: steam fixation 2.5 min,rolling 5 min,60? drying 4 h.Under these conditions,the contents of flavonoids,terpene lactones,polysaccharides,and tannins in Ginkgo biloba tea were 6.12 mg/g,1.356 mg/g,57.02 mg/g and 8.64 mg/g respectively.The content of amino acid,+C and GA were 45.68 mg/g,0.68 mg/gand 0.46 mg/g,respectively.The tea was brewed for 15 minutes at 100°C for the first time,the corresponding health and flavor substances in the tea infusion were 38.78 mg/L,19.12 mg/L,926.56 mg/L,40.43 mg/L and 322.35 mg/L,11.09 mg/L 5.14 mg/L,respectively.The phenol-ammonia ratio was 0.169.The content of ginkgo acid and cyanide in ginkgo biloba health tea can reach the safety requirements of Chinese tea national standard. |
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