Identification of 3-methoxytyramine as a specific biomarker for beet-sugar-fed honey: A two year surveillance study in South Korea

Honey is highly vulnerable to food fraud, and there are growing concerns about product authenticity. The commonly used stable carbon isotope ratios in the Calvin (C3) and Hatch-Slack (C4) photosynthesis cycles in plant feed cannot distinguish between beet-sugar-fed honey and natural honey. However, 3-methoxytyramine (3-MT) can be used as specific biomarker for identifying adulteration of beet-sugar-fed honey. In this study, we developed an isotope dilution-liquid chromatography/tandem mass spectrometry method to quantify 3-methoxytyramine (3-MT) in beet-sugar-fed honey. Solid phase extraction was used to quantify 3-MT and to reduce the matrix interference from honey samples. The limit of quantification was 1 μg kg^-1. The accuracy (recovery, %) and precision (relative standard deviation) values, determined in three laboratories, were 100-114 % and 1.25-9.07, respectively. Moreover, 3-MT was detected (1.07-10.7 μgkg^-1) in 144 out of 3046 samples collected from different parts of Republic of Korea over 2021 and 2022. The mean 3-MT concentration of seven honey samples fed with 100 % beet sugar was 5.32 μg kg^-1. The results of our study validated the accuracy and sensitivity of the proposed analytical method was established for quantification of 3-MT in honey samples. Additionally, our study demonstrated that the 3-MT as a reliable biomarker for beet-sugar-fed honey adulteration. Thus, our study presents a novel mass spectrometric approach for authentic honey discrimination with potential application in honey authenticity testing.