Abstract: Traditionally, authentication of organic foods requires measuring a variety of parameters before making a comprehensive evaluation, which suffers from the tedious sample preparation and low discrimination accuracy. To address this problem, in this study, a method of identifying organic tomatoes based on stable isotope ratio mass spectrometry (IRMS) and high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) combined with partial least squares discriminant analysis (PLS-DA) was proposed. Specifically, 94 tomatoes were collected, of which 50 were grown organically, while the rest were grown in traditional ways. Each sample was homogenized and freeze-dried before chemical analysis. Nitrogen isotope ratio (δ15N) data and HPLC-HRMS data were acquired. Taken into consideration of all measured factors, a PLS-DA model for discriminating organic tomatoes was established, which was used to select and confirm 13 representative indicators including δ15N, organic acids, and flavonoids. The accuracy of the model was 93.4%, which could meet the requirement for the identification of organic tomatoes. This study provides an advanced approach for discriminating organic tomatoes quickly.

Key words: organic tomato; isotope ratio mass spectrometry; liquid chromatography-high resolution mass spectrometry; partial least squares-discriminant analysis