Honey moisture explained

The threshold

Most honey sits between 15 and 20 per cent water. The Codex Alimentarius standard and the EU honey directive both set a maximum of 20 per cent for most honey, with allowances for a few types. Above roughly 20 per cent, osmotolerant yeasts naturally present in honey can ferment it.

That single number is why bees cap cells only when the honey is ready, why beekeepers use a refractometer before extracting, and why honey stored badly in a damp kitchen can spoil despite being famous for not spoiling.

What moisture decides

Some honeys are naturally at the extremes. Inland Australian honeys from arid country sit at 13 to 15 per cent, which is why grey box and yapunyah are so dense. Tropical honeys frequently sit at 19 to 22 per cent because the ambient humidity makes further evaporation impossible.

Why stingless bee honey is different

Stingless bee honey runs at 22 to 30 per cent water and does not meet the Codex standard, which was written around Apis mellifera honey. It ferments readily and is frequently refrigerated or dehydrated as a result.

Honey is hygroscopic

Honey draws water from the air. A jar left open in a humid kitchen gains moisture at the surface, and that surface layer can ferment while the rest is fine. This is the realistic route to spoiling honey and it is entirely preventable.

• Keep the lid on. This is most of the advice.
• Store at room temperature in a cupboard, not in the fridge and not on a sunny windowsill.
• Never put a wet spoon in the jar — it adds both water and organisms.
• If honey smells of alcohol or has a frothy layer, it has fermented.

How beekeepers manage it

1. 1Wait for cappingA capped cell is the bees' own signal that moisture is low enough. Extracting uncapped frames is the commonest cause of high-moisture honey.
2. 2MeasureA refractometer reads water content directly and costs very little.
3. 3DehumidifyA warm room with a dehumidifier will reduce moisture in supers before extraction.
4. 4Store sealedIn airtight containers, since honey will reabsorb moisture from a damp store.