Tracing the geographical origin of grain vinegar using the stable isotope ratio mass spectrometry and chemometrics

Abstract

Shanxi extra-aged vinegar (SX) and Zhenjiang vinegar (ZJ) are prominent vinegar varieties in China, but they frequently fall victim to counterfeit products due to their exclusive geographical indication labels. In this study, the carbon isotope ratio data (δ13C) obtained via elementary analyzer isotope ratio mass spectrometry (EA-IRMS) were employed to effectively distinguish between the two geographical indications of vinegar (SX and ZJ) and other vinegar samples sourced from different regions. The δ13C values were individually measured for vinegar (δ13Ctotal), the protein content extracted from vinegar (δ13Cprotein), and the sugar content extracted from vinegar (δ13Csugar). The results revealed that vinegars with exceptionally low sugar and protein contents can be precisely differentiated from the two geographical indications by directly comparing the δ13Cprotein and δ13Csugar values. Moreover, a linear discriminant analysis (LDA) discriminant analysis model was established, integrating all three δ13C isotope ratio datasets as multi-indicators. The results demonstrated that the proposed model distinctly discriminates 24 SX and 35 ZJ vinegar samples from the remaining 26 vinegar samples. This data indicated that the combination of EA-IRMS and LDA offers a potent tool for enhancing vinegar traceability and safeguarding geographical indications.