Detection of Adulteration in Manuka Honey with Low-Cost Honeys Using Untargeted Metabolomics and ATR-FTIR Fingerprinting: A Preliminary Study

Detecting the adulteration of high-value honeys such as Ma̅nuka with lower-cost varieties is challenging due to similarities in their chemical profiles. This study employed untargeted MS metabolomic profiling and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy to identify the adulteration of Ma̅nuka honey with Ka̅nuka and Ka̅mahi honeys at varying levels (2%, 5%, 10%, 20%, 30%, and 40%). Metabolomic analysis was conducted using ultra-high-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap-MS), while ATR-FTIR spectral ranges of 1700–900 cm–1 and 1700–600 cm–1 were used to detect Ka̅nuka and Ka̅mahi adulteration, respectively. Linear discriminant analysis (LDA) was applied for classification, and principal component analysis (PCA) revealed that heat treatment can significantly affect ATR-FTIR spectra. These preliminary findings indicate that untargeted metabolomic profiling may have the potential to support the confirmation of adulteration, while ATR-FTIR could provide a rapid and practical option for the routine screening of Ma̅nuka honey adulteration.