EA-IRMS: Detection of honey adulteration using isotope fingerprints

Significance of the Topic

Honey adulteration with low‐cost C4 plant sugar syrups undermines product quality, food safety and consumer confidence. Reliable detection of added sugars is essential for quality control laboratories and regulatory agencies seeking to ensure honey authenticity and protect both producers and consumers.

Aims and Overview of the Study

This application brief demonstrates the use of elemental analyzer–isotope ratio mass spectrometry (EA-IRMS) to measure carbon isotope ratios (δ13C) in bulk honey and corresponding extracted proteins. The goal is to detect adulteration with C4‐derived sugar syrups in compliance with AOAC 998.12 guidelines.

Methodology

The study follows these key steps:

• Protein extraction: 15 g of honey mixed with 3 mL water, heated to 80 °C, acidified and precipitated with tungstic solution according to AOAC 998.12, then washed and dried.
• Sample preparation: 100–200 µg of either bulk honey or isolated protein loaded into tin capsules.
• Combustion: Samples combusted in the Thermo Scientific™ MAS Series Autosampler reactor under oxygen to generate CO₂ gas.
• Isotope analysis: CO₂ introduced via Thermo Scientific™ ConFlo™ IV interface into the IRMS. Automated data acquisition using Thermo Scientific™ Isodat™ software to determine δ13C values.

Instrumentation

The following equipment was employed:

• Thermo Scientific™ EA IsoLink IRMS System
• Thermo Scientific™ MAS Series Autosampler and combustion reactor
• Thermo Scientific™ ConFlo™ IV Universal Interface
• Thermo Scientific™ DELTA V IRMS with Isodat™ Software Suite

Main Results and Discussion

Analysis of three honey batches and their protein fractions yielded δ13C values for both sample types within a narrow range of less than 1‰ difference, indicating no C4‐sugar addition. Average δ13C values for bulk honey samples ranged between –23.6‰ and –24.17‰, and protein fractions between –24.01‰ and –24.49‰. Natural isotopic variability allows detection of at least 7 % C4 sugar addition. Repeatability of measurements confirms the method’s sensitivity to minimal adulteration levels.

Benefits and Practical Applications

This isotope fingerprinting approach offers:

• Robust verification of honey authenticity in compliance with established guidelines.
• High throughput: up to 800–1000 samples before reactor maintenance.
• Reliable detection of low‐level adulteration (>7 % C4 sugars).
• Applicable to quality assurance in food industry and regulatory testing.

Future Trends and Applications

Emerging developments may include:

• Multi‐isotope profiling (e.g., δ18O, δ2H) to further refine geographic origin assignments.
• Coupling liquid chromatography to IRMS for compound‐specific isotope analysis.
• Miniaturized or field‐deployable IRMS systems for on-site screening.
• Integration with blockchain traceability and advanced chemometric models for comprehensive honey authentication.

Conclusion

EA-IRMS analysis of δ13C in both bulk honey and extracted proteins provides a sensitive, reproducible tool to detect C4‐sugar adulteration in honey. Following AOAC 998.12, laboratories can ensure product integrity, support regulatory compliance and safeguard consumer trust.

References

1. AOAC International. Official Methods of Analysis, Method 998.12: C4 Plant Sugars in Honey by Stable Carbon Isotope Ratio Analysis. AOAC, 1999.
2. Kracht O., Rácz-Fazakas T., Hilkert A. 13C and Simultaneous 18O and 2H Isotope Analysis in Ethanol with DELTA V Mass Spectrometers. Thermo Fisher Scientific Application Note No. 30147, 2008.