Abstract:
To investigate the correlation between growing environment and stable isotopes and mineral elements in 80 Yunnan large-leaf sun-dried green tea samples (from 4 production areas: Ning'er County, Lianghe County, Simao District and Jinghong City, Yunnan Province), 24 trace elements, 14 rare earth elements and 5 stable isotopes were analyzed and determined by using Elemental Analyzer-Isotope Ratio Mass Spectrometry (EA-IRMS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). To explore the feasibility of discriminating large-leaf sun-dried green tea from different geographical origins, multiple multivariate statistical methods were employed, including analysis of variance (ANOVA), principal component analysis (PCA), orthogonal partial least squares-discriminant analysis (OPLS-DA), and linear discriminant analysis (LDA). Tea from Lianghe County recorded a significantly higher total mineral element content compared to the other three regions (
P<0.05). PCA extracted seven principal components with a total cumulative variance contribution rate of 80.831%. An OPLS-DA model provided effective differentiation of samples from the 4 different regions, from which 15 key variables with variable importance in projection (VIP) scores >1 were screened (
δ2H,
δ18O, Rb, Al, Tl, Cs,
δ34S, Mn, Cu, Cd, Ga, Ba, Fe, As, Sr). Subsequently, these markers were subjected to Fisher's LDA. This model achieved 100.0% correct discrimination and a 92.5% cross-validation rate, demonstrating its robust capability for origin traceability of Yunnan large-leaf sun-dried green tea. This study demonstrated the feasibility of tracing the geographical origin of Yunnan large-leaf sun-dried green tea through mineral element and stable isotope analysis. The findings provided a research foundation for origin discrimination at a more accurate geographical scale and for the protection of geographical indication products in Yunnan.