Stable carbon isotope ratios for organic acids in commercial honey samples

Stable carbon isotope ratios (delta C-13) for glucose, fructose, disaccharides, trisaccharides, and organic acids in 116 commercial honey samples were measured by LC/IRMS. On the basis of EA/IRMS and LC/IRMS authenticity criteria, 39 of the samples were judged to have been adulterated. The delta C-13 values for organic acids from pure honey, reported here for the first time, ranged from -33.6 to - 26.5 parts per thousand. The mean Delta delta C-13 (glucose-organic acids) value was +3.7 +/- 0.9 parts per thousand. Glucose and organic acid delta C-13 values were strongly correlated (R = 0.71, P < 0.001). Gluconic acid, the predominant organic acid in honey, has been reported to be produced via decomposition of glucose by bee glucose-oxidase and certain Gluconobacter spp. This fact was confirmed by isotope analysis.