Influence of leaf age, species and soil depth on the authenticity and geographical origin assignment of green tea

Abstract

Rationale Stable isotope fractionation occurring during leaf growth provides internal characteristics for identifying the geographical origin, traceability and authentication of tea. Studying the influence of leaf age, species and the relationship with the cultivated soil may reveal previously undocumented stable isotope fractionation mechanisms, and provide a deeper understanding of the physiological isotopic effects on the tractability and authentication accuracy of green tea to combat mislabeling and fraudulent conduct. Methods A total of 36 pairs of young (one bud with one leaf) and mature growth (older leaf) samples from two species of Longjing tea (Longjing #43 and Colonial cultivar) and corresponding cultivation soil samples from two different depth layers (0–20 cm and 20–40 cm) were collected in Westlake district, Hangzhou, Zhejiang province, China. Four stable isotope ratios (δ13C, δ15N, δ2H, and δ18O values) were measured using an elemental analyzer coupled with an isotope ratio spectrometer. Linear correlation and one‐way analysis of variance (ANOVA) statistical analyses were performed to investigate isotopic fractionation mechanisms during plant growth, and reflect the dynamic physiological processes from soil to leaf. Results The carbon and nitrogen isotope ratios (δ13C and δ15N values) reflected the absorption, migration and fractionation of carbon dioxide and nitrogenous nutrients during photosynthesis, nutrient uptake, nitrogen fixation and leaf respiration. The water isotope ratios (δ2H and δ18O values) reflected the use and fractionation of water by tea plants at different growth stages. Conclusions Considerable differences were found for hydrogen and oxygen isotope ratios according to leaf age, revealing complex isotopic fractionation mechanisms and possible interference factors. Leaf maturity effects should be considered, as they will influence the precision and accuracy of models when assigning the geographical origin, traceability and authentication of tea.

Geographical traceability of Chinese green tea using stable isotope and multi‐element chemometrics

“…), environmental and climatic variables ( 2 H/ 1 H, 18 O/ 16 O and 13 C/ 12 C ratios) and local agricultural practices ( 15 N/ 14 N ratios) are assimilated by the plant, and can be simultaneously used to measure external influences related to the geographical origin . The origin and traceability of tea are more accurately described by the close relationships of stable isotope ratios and multi‐element compositions influenced not only by the soil chemistry, but also the entire ecological system including cultivation practices . Many studies have successfully applied single or bivariate analysis to stable isotope ratios and element concentrations to discriminate the geographical origins of tea separated by large‐scale distances (countries); however, for small‐scale distances (provinces or even localized zones in the same province), these strategies based on a single or bivariate analyte(s) are not robust enough to make an accurate assessment.…”

Achieving Food Authenticity and Traceability Using an Analytical Method Focusing on Stable Isotope Analysis

“…In the EU, this approach has been applied since the late 1990s to trace the geographical origin of agricultural and food products such as cereals [29][30][31][32][33][34][35][36][37][38] , meat 26,[39][40][41][42][43][44][45][46][47][48][49][50] , dairy products [51][52][53][54][55][56][57][58] , olive oil [59][60][61][62] , honey [63][64][65][66] , coffee, and tea [67][68][69][70][71][72][73][74][75] . Table 1 shows a list of previous studies that traced the geographical origin of food materials using stable isotope analysis, mainly since 2000.…”

Stable isotope characterization of tobacco products: A determination of synthetic or natural nicotine authenticity

“…20 Rogers and co-workers demonstrated that leaf age, species, and the relationship with cultivated soil were also key factors affecting stable isotope fractionation. 21 At present, literature reports indicate that stable isotopes in tobacco are closely related to geographic origin. 22,23 Meanwhile, Chung et al successfully demonstrated compoundspecific δ 13 C and δ 15 N analyses of fatty acids and amino acids for improving the authentication of organic milk against conventional milk collected in Korea.…”

“…Nitrogen isotopes in plants are affected by farming practices 20 . Rogers and co‐workers demonstrated that leaf age, species, and the relationship with cultivated soil were also key factors affecting stable isotope fractionation 21 . At present, literature reports indicate that stable isotopes in tobacco are closely related to geographic origin 22,23 .…”