Isotope signature study of the tea samples produced at four different regions in India

Abstract

India ranks second in the world for tea production and is well known for Darjeeling tea, which has great demand in the world market due to its unique flavor. In the present study, the combination of isotopic composition of Sr (as ⁸⁷Sr/⁸⁶Sr) and C (as δ¹³C) was studied as geographic tracing signatures for Indian tea samples grown in different regions. Authentic tea leaves as well as soil samples were collected from different tea producing regions; namely, Assam, Darjeeling, Munnar and Kangra, which are geographically distinct from one another. Isotopic analyses were performed by Multi-Collector Inductively Coupled Plasma Mass Spectrometry and Elemental Analyzer-Isotope Ratio Mass Spectrometry for Sr and C, respectively. On the basis of Sr isotopic data, Darjeeling tea samples were found to be more radiogenic than the other tea samples, with changes in the ⁸⁷Sr/⁸⁶Sr ratio being an excellent geographic indicator. Variations in δ¹³C proved to be an excellent geographic indicator for Munnar and Kangra teas. The ⁸⁷Sr/⁸⁶Sr values were statistically identical in both the soil and the tea. Principal Component Analysis (PCA), using the combination of ⁸⁷Sr/⁸⁶Sr, δ¹³C and strontium concentration data, was used to effectively differentiate among different tea producing regions.