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Assurance that honey has not been adulterated with sugars of C4 origin (e.g. high fructose corn syrup or invert cane sugar) is carried out by the internationally recognised AOAC 998.12 C4 sugar adulteration test. In the past decade, there have been concerns around the applicability of this test to mānuka honey due to honey with a high concentration of methylglyoxal (MGO, >250 mg/kg) often failing the test.  It is this same high MGO content that makes manuka honey such a premium product. This paper reviews the literature to determine possible causes for this failure and identifies more suitable methods of analysis that can be applied to detect syrup addition to manuka honey.

Read the full open access paper here

The official AOAC method for  the detection of C₄ derived exogenous sugars, such as cane sugar or high fructose corn syrup, in honey is based on stable-isotope ratio mass spectrometry analysis of δ¹³C value of honey versus δ¹³C of honey protein. However, this method gives false positives with certain Australian honeys, especially those from the Leptospermum species such as Manuka honey. Australian researchers have improved the method, which not only determines the isotopic values of “proteins” precipitated using the standard AOAC method, but also “proteins” precipitated after incorporation of a further modification step, which removes insoluble material (including pollen) from the honey before precipitation. The modified method includes the analysis of different isotopes of the precipitated protein, sugar profiles and Manuka markers. This new method will detect residual sugar feeding of bees, as well as the adulteration of honey with C₄ sugar.

Read the abstract here