Authenticity Certification of Pu'er Raw Tea in Different Years Based on the Stable Isotope Ratios of Carbon and Nitrogen in Caffeine and Amino Acids

The method of carbon and nitrogen stable isotope ratio analysis in caffeine and amino acids (gas chromatography combustion isotope ratio mass spectrometry, GC-C-IRMS) was used to carry out the authenticity certification of Pu'er raw tea in different years. Chemometrics analysis showed that the stable isotope ratios of carbon and nitrogen in caffeine and amino acids combined with chemometrics model could effectively distinguish Pu'er raw tea in different years. And the accuracy of prediction and verification were more than 80%, BP-ANN had the best certification performance, whose accuracy of prediction and verification were 100%. Through further screening and identification, three chemical markers of Pu'er raw tea in different production years were obtained, which included δ¹⁵N_Thea、δ¹³C_glu and δ¹⁵N_Glu. Therefore, the analysis method of carbon and nitrogen stable isotope ratios in caffeine and amino acids based on GC-C-IRMS could be used to authenticate the authenticity of Pu'er raw tea in different years. This study preliminarily established the index system and technical system of Pu'er tea product certification, which also provided research ideas and method references for other food certification research.