| Tea is one of the worldwide popular beverages which is consumed by two third of the world population. China is a gaint producer of tea and tea products. Chinese tea can be divided into Green, Red Black, Oolong, White and Yellow tea due to the colour and the processes methods. Tea is a conbination of nature and human activities, the final tea product was obtained under certain soil and climate conditions, through various cultivation ways and different processing methods (both traditonal and modern ones) as well as classification. Therefore, the geographical and natural conditions will determine the qualities of agricultural products grown there, so does the mineral elements in plants, they have close relationship with the growing environment such as water, atmosphere and soil conditions. Mineral elements in tea reflect the elemental conditions of the growing soil environment, geological environment directly or indirectly influenced the the water, fertilizer, gas and heat in soil thus lead to soil attribute differences, plus the processing technology differences, would eventually lead to different tea quality and style. To protect Chinese tea brand and quality of authenticity, our country make the related provisions of provenance protection and the geographical indication protection, many researchers have done researches on tea authentication through the near infrared spectrum analysis, X-ray fluorescence technology, thermal analysis technology, sensory evaluation methods, chromatography detection methods, etc. However, by using mineral elements to determine tea origin and breed in China is almost empty. The current study reveals the diversity of tea samples form different breeds and producing areas, through analysis of 32 mineral elements in the fresh tea leaves and finished tea products, aim at provide basis for the origin discriminant study on tea in our county.The first period of this study, we apply the airtight microwave digestion method on the pretreatment of tea samples, then established a ICP-OES and ICP-MS methods of detecting 32 elements in tea leaves through the national standard material verification tests, the labeled recovery experiment, detection limit experimental and computational relative standard deviation, and the results show that airtight microwave digestion method and the ICP-MS/ICP-OES detection method of elements of the tea method is accurate, reliable, with high precision and repeatability. On this basis, we collected at one time different steamed green tea sample form Chongqing BaNanErSheng tea factory(LongJing #43, Bayu earlier, Pingyang earlier, Meizhan, NanJiang #2, FuDingdabaicha, etc) and steamed green tea samples from different regions of Chongqing (BaNan, NanChuan, WanSheng, YongChuan, RongChang, ShaPingBa GeLe Shan), we also collected the tea products samples from different regions of Chongqing (BaNan, NanChuan, WanSheng, YongChuan, RongChang, KaiXian), then analysis 32 mineral elements in 20 samples with different breeds but from the same producing area,17 steamed green tea samples from different producing areas and 17 finished tea products samples from different producing areas. Then we incorporated the principal component analysis and cluster analysis to determine the tea varieties differences and regional differences, the results are as follows:32 mineral elements are detected from different varieties of steamed green tea samples, including a kind of macroelement,15 kinds of rare earth elements and other 16 trace elements. Principal component analysis results showed that the YunKang-14 has a strong absorbtion effect on all the rare earth elements, Longjing tea leaf, Qingxin Oulung, Yellow Guanyin, FuDing dahao and YingShuang share certain similarity; And Meizhan Pingyang earlier have weak adsorption ability of rare earth elements and they share certain similarity. Yunnan big leaf population and the NanJiang #2 shows distinct difference on absorbtion ability of Pr、Al、Mn elements, but the rest of the samples show no specificity on absorbing those elements. Clustering analysis and principal component analysis have certain similarities, Yunnan big leaf population, YunKang #14 and the NanJiang #2 gather into three different clusters, and YunKang #14 has weaker absorbing ability of most of the elements than the ability of Yunnan big leaf population and the NanJiang #2. The results indicate that the breeds of tea could be determined through element analysis.Mineral elements in steamed green tea samples from different areas display that YongChuan samples has the least earth element content, Chongqing GeLe mountain samples, WanSheng #3 samples, BaNan YiPinTang tea factory samples containing higher quantity of rare earth elements compared to other samples, this illustrate that these several regions’local soil have higher content of rare earth elements, and different breeds have different absorbing ablility of rare earth elements. Ba elements in Rongchang R1 sample is higher than other regions samples, Ba element is one important basis of distinguish soil geology. Samples of BaNa and NanChuan area has lower Ca, Sr, Al element content than samples from other areas, especially YongChuan and WanCheng district, this accounts for the specific features of the Ca、Sr、Al in these four areas. Clustering analysis shows that three samples form YongChuan are in one category, the samples form NanChuan region are in one same category except one sample-the N1, samples from BaNa area are mostly in one category, the sample Nl from NanChuan and samples B19#, B20# from BaNan are not classified into the samples from the same producing areas, but classified into another category with samples from adjoining areas, samples are with similarities. The rest including KaiXian samples, RongChang samples show no certain patterns. This chapter safely draw the conclusion that, By analysis and comparision of the 32 mineral elements from the fresh tea leave samples from typical tea producing areas in ChongQing, results show that mineral elements in fresh tea leaves from different producing areas differ greatly from each other, content of most rare earth elements could play important role in distinguishing characteristics of producing areas and characteristic element of each area diverse.Mineral elements of finished tea product samples form different areas of ChongQing show that:rare earth elements provides the basis for the identification of tea producing region, similarity of elements content exsits in the tea samples from the same region, but also have content difference, so the distribution, clustering are all relatively disordered, this may be because of the elements gathering such as Cr, As, Pb, Fe, etc after tea processing; the other reason is there is not enough samples, therefore, it’s hard to get the accurate characteristic elements in finished tea product samples by statistic analysis.These results above demonstrate that:mineral elements in tea leaves from different breeds are variant and the mineral elements in tea influenced by the producing regions, therefore, it’s feasible to determin tea characteristics of origin through the mineral elements discriminant analysis. |
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