Determination of authenticity of Manuka honey by MALDI-TOF mass spectrometry

Importance of the Topic

Manuka honey commands a premium price due to its unique antimicrobial, antioxidant and anti-inflammatory properties. Its limited production and high market value make it susceptible to adulteration and mislabeling. Reliable analytical methods are essential to ensure authenticity, consumer protection and regulatory compliance.

Goals and Overview of the Study

This work evaluates, for the first time, a MALDI-TOF MS–based workflow to detect characteristic Manuka honey markers, enabling rapid differentiation between authentic Manuka products and non-Manuka honeys.

Methodology and Instrumentation

Honey samples labeled as “Manuka” and blossom honeys were obtained from local retailers. To remove dominant sugars and enrich key polyphenols, samples underwent reversed-phase SPE extraction using Strata-X cartridges, with water washing and 2% TFA in methanol elution. Extracts were analyzed by:

• Shimadzu MALDI-8030 linear TOF mass spectrometer (positive ion mode) for rapid MS profiling of polyphenols.
• Shimadzu MALDI-7090 TOF/TOF mass spectrometer (high-energy CID MS/MS) for structural confirmation against standards.

Key Results and Discussion

Direct MALDI analysis of crude honey produced intense sugar signals that suppressed minor markers. SPE enrichment yielded clean spectra with distinct polyphenol profiles.

• Manuka honey exhibited specific markers: leptosperin (m/z 559 [M+Na]+), 4-hydroxyphenyllactic acid (m/z 205), 3-phenyllactic acid (m/z 189) and 2-methoxybenzoic acid (m/z 175).
• Flavonoid components such as chrysin, pinocembrin, apigenin, pinobanksin, luteolin and 8-methoxykaempferol were identified in Manuka samples.
• High-energy CID MS/MS confirmed marker identities through comparison with commercial standards and expected fragmentation patterns.
• Non-Manuka blossom honey lacked these characteristic signals, demonstrating clear differentiation.

Benefits and Practical Applications

• The proposed MALDI-TOF workflow allows high-throughput screening of honey authenticity without extensive chromatographic separation.
• SPE-MALDI-TOF approaches reduce sample preparation time and solvent use.
• Identification of multiple markers increases confidence in authenticity assessments for quality control and regulatory enforcement.

Future Trends and Potential Applications

• Extension of this approach to other premium honey varieties and natural products.
• Integration with chemometric models and machine learning for automated classification.
• Development of portable MALDI-TOF instruments for on-site authenticity testing.
• Creation of comprehensive spectral libraries to support regulatory databases and industry standards.

Conclusion

The SPE-MALDI-TOF MS workflow offers a rapid, sensitive and reliable method to authenticate Manuka honey by detecting key chemical markers. This approach can support industry, regulators and researchers in combating food fraud and ensuring product integrity.

References

1. Leptospermum scoparium. Wikipedia. (Accessed 2023).
2. Unique Manuka Factor UMF Honey Association. (Accessed 2023).