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Why does honey crystallise, and has it gone bad?

Honey propertiesReviewed 2026-08-02

Short answerFalseEstablished evidence

Crystallised honey has not gone bad. Honey holds more glucose than its water can dissolve, so the glucose gradually comes out of solution as crystals. How fast depends mainly on the glucose-to-fructose ratio — acacia can stay liquid for over a year, rapeseed can set inside the comb. To reverse it, stand the jar in water at 40-50 °C; never use a microwave.

Where the belief comes from

Most foods that change texture in a cupboard have gone wrong, so the inference is reasonable. It is reinforced by the fact that mass-market honey is processed specifically to stay liquid, which has made clear runny honey look like the normal state when it is the engineered one.

What is happening

Honey is supersaturated. Glucose is far less soluble than fructose, so it reaches saturation first and crystallises out as glucose monohydrate, leaving a fructose-rich syrup between the crystals. A honey with proportionally more glucose sets sooner — which is why the sugar ratio predicts the rate better than colour, price or anything on the label.

Temperature matters too: granulation is fastest at around 14 °C, which is close to the temperature of many kitchen cupboards and unheated larders. And crystals need something to start on — pollen, dust, existing crystals — which is why ultrafiltered honey stays liquid far longer.

What it does not mean

  • It does not mean the honey has spoiled.
  • It does not mean the honey is adulterated. If anything the reverse: removing pollen delays it.
  • It does not prove the honey is raw. Plenty of processed honey granulates eventually, and some raw honeys stay liquid for a year.

What to do

Either eat it as it is — set honey spreads better and does not run off toast, which is the whole commercial argument for creamed honey — or warm it gently in a water bath at 40-50 °C, stirring occasionally. High heat destroys aroma compounds and raises hydroxymethylfurfural, and a microwave does it fast and unevenly. It will set again, usually sooner, because some crystal nuclei survive.

Sources

  • Crystallisation of honey: mechanisms and control — Peer-reviewed food-science literature · Peer-reviewed article

How sources are selected and weighted is set out in the sources and evidence policy.

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