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, gently handled honey contains almost no HMF, which is why its level is considered a reliable indicator of whether a honey was heated too strongly or stored too warm. The higher the measured value, the more likely it is that the gentle handling required of good honey was violated during liquefying, bottling, or transport.
The Honey Regulation (Germany) legally permits an HMF content of up to 40 milligrams per kilogram, and for honey from tropical regions even up to 80 milligrams per kilogram. The German Beekeepers' Association sets a markedly stricter value for its Echter Deutscher Honig trademark, at most 15 milligrams per kilogram, and for varieties that are naturally low in enzymes, only 5 milligrams per kilogram. The voluntary German Honey Guidelines (Leitsätze), part of the German food code (Deutsches Lebensmittelbuch), additionally have even stricter quality tiers: in the Auslese category at most 15, and in the Premium or feine Auslese categories only 10 milligrams per kilogram are permitted.
For practice this means a beekeeper should never heat their honey strongly over an extended period, for instance to liquefy it faster, since just a few hours at too high a temperature can noticeably raise the HMF value. A common misunderstanding is confusing HMF with a freshness marker; in fact the value mainly says something about handling after the harvest, not about the original quality of the nectar or honeydew.