Open Access
Volume 39, Number 5, September-October 2008
Page(s) 574 - 587
Published online 28 October 2008
Apidologie 39 (2008) 574-587
DOI: 10.1051/apido:2008042

Improved detection of honey adulteration by measuring differences between 13C/12C stable carbon isotope ratios of protein and sugar compounds with a combination of elemental analyzer - isotope ratio mass spectrometry and liquid chromatography - isotope ratio mass spectrometry ($\delta$13C-EA/LC-IRMS)

Lutz Elflein and Kurt-Peter Raezke

APPLICA GmbH - Applied Chemical Analysis, Olof-Palme-Str. 8, 28719 Bremen, Germany

Received 31 January 2008 – Revised and accepted 10 July 2008 - Published online 28 October 2008

Abstract - The detection of honey adulteration with invert sugar syrups from various C3 and C4 plant sources was realized by coupling an isotope ratio mass spectrometer both to an elemental analyzer and to a liquid chromatograph (EA/LC-IRMS). For 451 authentic honeys measured, the individual $\delta^{13}$C values of bulk honey, its protein fraction, fructose, glucose, and di- and trisaccharides ranged from –22.5 to –28.2‰  and did not show differences ( ${\rm\Delta} \delta ^{13}$C) of more than $\pm
$ 0.9‰  (average), with a maximum standard deviation of 0.7‰. The ${\rm\Delta} \delta ^{13}$C (fructose – glucose) value was significantly lower (0 $\pm
$ 0.3‰). Based on the obtained results and considering a confidence level of 99.7%, the following limits for ${\rm\Delta} \delta ^{13}$C values of authentic honey are proposed: ${\rm\Delta} \delta ^{13}$C max.: $\pm
$ 2.1‰  (maximum difference between all measured $\delta^{13}$C values); ${\rm\Delta} \delta ^{13}$C fru – glu: $\pm
$ 1.0‰; ${\rm\Delta} \delta ^{13}$C (‰)  protein - honey: $\geq$ – 1.0‰. The newly developed EA/LC-IRMS method and the purity criteria defined represent a significant improvement compared to existing methods.

Key words: honey / adulteration / LC-IRMS / EA-IRMS / $\delta$13C values / C3 sugar / C4 sugar

© INRA, DIB-AGIB, EDP Sciences 2008