HMF in honey

HMF (hydroxymethylfurfural) is a by-product of fructose breakdown in honey, formed during storage or heating. It is virtually absent in fresh honey, so FAO treats it as the main indicator of honey deterioration. It is measured in milligrams per kilogram of honey.

Directive 2001/110/EC sets a limit of 40 mg/kg after processing and blending (except baker’s honey) and 80 mg/kg for honeys of declared origin from tropical regions. For honeys naturally low in enzymes, such as citrus honey, a diastase of 3 instead of 8 is accepted if HMF does not exceed 15 mg/kg. Protected names can be stricter: Kraški med allows at most 15 mg/kg at filling. HMF rises faster with more moisture, lower pH and higher temperature, and faster still after heating. According to FAO, a syrup made by acid hydrolysis can also give a high value.

Why this matters to you: HMF is a simple way to tell whether honey was overheated or stored too long. According to FAO, deteriorated honey does not become dangerous, but it loses part of its flavour and other qualities. To keep HMF low at home, keep the jar away from heat.