Honey is one of the most adulterated foods by addition of sugar syrups. Most if not all commercial honeys derive from the nectar of C3 plants. Sugar syrups derived from cane sugar or maize, which are C4 plants. The accepted standard method to check C4 sugar adulteration, is to determine the δ¹³C (C13/C12 ratio) by SIRA mass spectrometry. Honeys that are tested with a δ¹³C value of -23.5 and lower are deemed to be pure. Honeys that have a δ¹³C value between -23.5 and -21.5, fall into a grey area. Honeys that have a δ¹³C of -21.5 or higher are deemed to be adulterated. However, false positives of syrup adulteration may occur if the bees have been collecting nectar from C4 plants, and hence low level adulteration is difficult to detect. This review discusses the background to testing honey by SIRA, and the limitations of this method.
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