An untargeted C-13 isotopic evaluation approach for the discrimination of fermented food matrices at natural abundance: Application to vinegar

摘要

A non-destructive and comprehensive C-13 isotopic evaluation approach based on H-1 NMR spectroscopy was developed. The carbon isotope distribution (CID) of most of the components (S/N >= 1000) in food matrices were evaluated using frequency distribution of peak area ratios (PAR) of decoupling to non C-13 decoupling spectra at natural abundance. The approach was applied successfully to vinegar and it was found that the PAR of fermented vinegars is obviously narrower than that of the blended one and the one produced via chemically defined culture medium. Besides, the extra additives can also be evaluated by their characteristic PAR values. It was found that the sugars are the most commonly added components into the blended vinegars. The results obtained from the developed approach show good validity (baseline effect, RSD < 0.1%) and internal reproducibility (RSD < 0.1%). Practicability of the method is confirmed by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) detection method. The results imply that the proposed approach could be used not only for the discrimination but also for the primary authentication of the blended components in the fermented food matrices.