Fermentation of honey is well known among beekeepers—particularly those who have been on the receiving end of having to clean up after fermented honey has ‘exited’ a drum under pressure. What many of us have less understanding of is the consequence of honey fermenting when it is packed in a jar for sale to a consumer.

An article on fermenting honey appeared in a previous edition of the journal (Howse, 2018), which provided a description of why honey ferments and what happens when it does. Under normal circumstances, bees will process or ‘ripen’ nectar or honeydew into honey with around 17–18% moisture in it.

When moisture levels are this low, the very high sugar concentration in the honey makes it more or less impossible for yeasts to grow. If moisture levels are higher, certain yeasts (osmophilic yeasts) are able to survive and grow.

They use the sugars in the honey as an energy source, and in doing so form ethanol (the form of alcohol found in beer and wine) and carbon dioxide (which builds up and causes pressure to grow inside the storage container). Honey with moisture levels of 19% or higher appear to be at high risk of fermenting.