HMF (Hydroxymethylfurfural)
Lexikon
HMF stands for hydroxymethylfurfural, a substance that forms from the sugar fructose when honey is heated or stored for a long time or incorrectly.
HMF stands for hydroxymethylfurfural, a substance that forms from the sugar fructose when honey is heated or stored for a long time or incorrectly. Fresh honey that has been handled gently contains hardly any HMF, which is why the content is considered a reliable indicator of whether a honey has been heated too much or stored too warm. The higher the measured value, the more likely it is that the gentle handling good honey requires was not observed during liquefying, bottling, or transport.
The Honey Ordinance legally permits an HMF content of up to 40 milligrams per kilogram, and even up to 80 milligrams per kilogram for honey from tropical regions. The German Beekeepers' Association sets a considerably stricter value of at most 15 milligrams per kilogram for its trademark Echter Deutscher Honig, and only 5 milligrams per kilogram for honey varieties that are naturally low in enzymes. The voluntary guidelines for honey of the German Food Code also include even stricter quality grades: in the Auslese category at most 15, and in the Premium or feine Auslese categories only 10 milligrams per kilogram are permitted.
In practice this means that a beekeeper should never heat his honey strongly for a longer period, for example to liquefy it faster, because just a few hours at too high a temperature can cause the HMF value to rise considerably. A common misconception is to confuse HMF with a freshness characteristic; in fact the value says something mainly about the handling after the harvest, not about the original quality of the nectar or honeydew.