Evaluation of honey authenticity in Lebanon by analysis of carbon stable isotope ratio using elemental analyzer and liquid chromatography coupled to isotope ratio mass spectrometry

Honey is one of the most valuable sweeteners consumed by humans all over the world. Consequently, it is often a target for adulteration through the addition of different sugar syrups during or after honey production, resulting in a reduction in its nutritive value. For the first time, this study analyzes honey samples of various botanical species collected from different Lebanese regions using element analyzer (EA) and liquid chromatography (LC) coupled with isotope ratio mass spectrometry (IRMS). The delta C-13 of bulk honey, its protein fraction, and the main individual sugars (glucose, fructose, disaccharides, and trisaccharide) were determined, in order to characterize and evaluate the authenticity of honey consumed in Lebanon. The results showed that the delta C-13 values for bulk honey and its protein range from -26.5 parts per thousand to -24.5 parts per thousand and from -26.4 parts per thousand to -24.7 parts per thousand, respectively, for authentic samples. delta C-13 values for samples adulterated with sugar syrups range from -11.2 parts per thousand to -25.1 parts per thousand for bulk honey and from -26.6 parts per thousand to -23.7 parts per thousand for its proteins, with a difference between bulk and protein values between -1 and -8.7 parts per thousand. Using LC-C-IRMS techniques, the delta C-13 of individual sugars provides additional information on the presence of undeclared sugars. We found that all authentic samples had Delta delta C-13(f-g) and Delta delta C-13 max values within the naturally occurring range of +/- 1 parts per thousand and +/- 2.1 parts per thousand, respectively, while the adulterated samples fall outside the Delta delta C-13 ranges. The oligosaccharide peak was detected in most adulterated samples.