Authenticity determination of honeys with non-extractable proteins by means of elemental analyzer (EA) and liquid chromatography (LC) coupled to isotope ratio mass spectroscopy (IRMS)

- Honeys with non-extractable protein were evaluated systematically for the first time.
- EA-IRMS and LC-IRMS were suitable for measurement of adulteration in honeys.
- Honeys with non-extractable protein were all identified as adulterated with C-4 or C-3 sugars.
- Large numbers of samples were analyzed to ensure reliability.
- Result obtained is highly recommended as a supplement to AOAC 998.12 method.

The present work aims to systematically demonstrate the authenticity of honeys with non-extractable proteins for the first time, by means of EA-IRMS and LC-IRMS. Fifty-three pure honeys of various botanical and geographical origins were studied and a criterion on the basis of the stable carbon isotope ratio characterization of total honey and the main sugars was established for pure honeys. Parameters such as δ13C values of total honey and the main sugars were well utilized to identify honeys with non-extractable proteins. Thirty-five honeys from which protein could not be extracted were all identified as adulterated with C-4 sugars or C-3 sugars. The use of isotopic compositions and some systematic differences permit the honeys with non-extractable proteins to be reliably identified. The findings obtained in this work could supplement the AOAC 998.12 C-4 sugar method, with regard to honeys from which protein cannot be extracted.