Speciation And Quality Standard Study Of Organic Selenium In Natural Tea

Selenium is closely linked to human health.Selenium in tea has anti-cancer,anti-oxidation,detoxification,blood fat reduction and immunity effects.Report to inorganic selenium,organic selenium has the characteristics of low toxicity and high bioavailability.In this study,tea was chosen as the research object.Firstly,the extraction method of organic selenium in tea was studied experimentally.On this basis,the optimal extraction scheme of organic selenium(containing protein selenium)was determined.Secondly,the preferred experimental scheme was used to The characteristics of organic selenium in natural tea samples from 14 provinces was analyzed.Then,according to different tea types,origins,and selenium extraction methods,the organic tea selenium was extracted from the natural tea or tea soup in the literature database.The content and ratio of the content and its relationship with the total selenium content were tested.Finally,the quality standards of organic selenium in tea were preliminaries combined with experiments,literature data and related quality standards.According to the selection of different extraction methods of organic selenium,the direct method(continuous dialysis method)and indirect method(water extraction method and the acid extraction method)were initially established as the extraction methods of organic selenium by searching literature.On this basis,the optimal extraction scheme of organic selenium was selected by comparing the experimental results.The results showed that the extraction efficiency of water extraction method(88.68%)was greater than other methods,and the operation was simple and feasible.Therefore,the best extraction method of organic selenium in tea is water extraction.In addition,in order to assist the study of protein and selenium in tea,the extraction method(sequential extraction method)and determination method(biuret method)of protein and selenium were selected through experiments.This study collected natural tea samples from different regions of China(East China,South China,Central China,Northwest China and Southwest China),and analyzed the indicators of total selenium,organic selenium,protein selenium and bioavailability in tea and tea soup.The results showed that the total selenium content of natural tea and tea soup in China was 32.45 ± 18.18 ?g/kg(7.29 ? 89.44 ?g/kg,n =19),0.09 ± 0.05 ?g/100mL(0.03 ? 0.23?g/100 mL,n = 18)..The content of organic selenium in tea and tea soup increased with the increase of total selenium content.There was no significant difference in total selenium between tea and tea soup in different regions(P > 0.05).The average content of total protein selenium in tea was14.29 ± 3.895 ?g/kg(n = 3),accounting for 45.70% of the organic l selenium content.The bioavailability of selenium in tea was 35.36 ± 23.01%(n = 19).In addition,the analysis of organic selenium in tea in the literature database showed that most of the tea samples were from Enshi,Hubei and Ziang,Shaanxi.The total selenium range of tea and tea soup was 850 ± 1.07 ?g/kg(30 ? 5540 ?g/kg,n =65)and 0.43 ± 0.27 ?g/100 mL(0.15 ? 0.99 ?g/100 mL,n = 15).By comparing the literature database and collecting tea samples,it is found that the selenium content of the former is significantly higher than that of the latter,which is related to the fact that the tea in the database is mostly from the selenium-rich areas of Ziyang and Enshi.Comprehensive analysis of tea samples and literature database of selenium content in the literature,this study initially proposed to divide tea into 5(< 200 ?g /kg;200 ? 400 ?g/kg;400 ? 600 ?g/kg;600 ? 1000 ?g/kg;> 1000 ?g/kg);and the ratio of organic selenium in tea or tea soup is ? 70% as the quality standard for selenium in natural tea in China.Similarly,referring to the current standard and the selenium content of tea,the natural selenium-enriched tea is divided into three groups(400 ? 600 ?g/kg;600 ? 1000 ?g/kg;1000 ? 4000 ?g/kg);and tea or tea soup organic selenium Percentage(? 80%).