Raw Honey vs Pasteurised: What Heating Changes
Heating changes honey less than the argument around it suggests: it raises one laboratory marker (HMF), lowers another (diastase), erodes aroma when it runs hot or long — and leaves the jar legally and practically what it was, honey. Pasteurisation here is a brief commercial step — flash-heating for a few seconds at around 70–78°C, then rapid cooling — done to dissolve the seed crystals that start granulation and to kill the yeasts that can ferment higher-moisture honey; it is not the safety measure the word implies from milk. Raw honey skips the step to keep what heat erodes. The rest is the detail: what the step is for, what moves, what does not, and how a UK label reads.
Pasteurised honey has been briefly flash-heated and rapidly cooled so that it stays liquid, clear and stable in the jar; raw honey has not been pasteurised or fine-filtered after extraction.
Plate I · IllustrationRecord
What is pasteurisation, in honey?
A borrowed word, and only the technique came across. Milk is pasteurised against disease organisms; honey is pasteurised against inconvenience. In Bogdanov’s account of commercial practice, honey is heated “to destroy honey crystals and yeasts”: a few seconds at 70–78°C, then rapid cooling to limit heat damage. Nothing in that is about making honey safe to eat.
Pasteurisation is not the same as ordinary warming. Every bottler warms honey — set honey will not pour, let alone pass a filter — and gentle practice keeps that at 40–50°C, where a day or two does no damage. Pasteurisation is the deliberate step beyond: hot enough, briefly, to wipe out yeasts and dissolve every seed crystal.
Why is honey pasteurised at all?
Two reasons, both commercial and both real.
Crystals first. Glucose-rich honeys set quickly once a few seed crystals exist to build on. Flash heating dissolves those seeds, so the honey stays liquid and bright on the shelf for far longer — and when it eventually sets, it does so slowly, in coarse crystals. Why honey sets, and why that is not a fault, is covered in crystallised honey.
Yeasts second. Honey naturally carries yeasts, and whether they matter is mostly a question of water. Below about 18 per cent water, honey keeps with little to no risk of fermentation; UK law permits up to 20 per cent (23 for heather). A honey in that upper band can ferment — especially if it part-sets, since crystallisation concentrates the remaining water into the liquid layer, where yeasts get to work. A packer cannot nurse thousands of jars through that risk; the yeasts are killed instead.
Fig. I · The two points between keeping and lawDiagram
Honey naturally carries yeasts, and whether they matter is mostly a question of water. Every mark on this scale is a figure this page states.
UK law permits
If it part-sets
Crystallisation concentrates the remaining water into the liquid layer, where yeasts get to work.
A direction, not a water figure. The page pins no jar and gives no figure for how far the water concentrates, so neither end of that travel is drawn against the scale — and the 20 bounds the composition of the honey, not a layer within it.
About 18 per cent
Below about 18 per cent water, honey keeps with little to no risk of fermentation. Drawn dashed because the page hedges it: little to no risk, not none.
20 per cent
UK law permits up to 20 per cent.
23 per cent — heather
23 for heather: its own permission, drawn as its own segment. Not an extension of the 20.
The band, 18 to 20
A honey in that upper band can ferment — especially if it part-sets, since crystallisation concentrates the remaining water into the liquid layer, where yeasts get to work. A packer cannot nurse thousands of jars through that risk; the yeasts are killed instead.
Two percentage points wide: that is the fermentation case for the heat step, at its real width. Neither purpose has anything to do with making the honey safe to eat.
What does heating measurably change?
UK law watches heat through two markers. Hydroxymethylfurfural (HMF) is a breakdown product of fructose that accumulates as honey is heated — or simply stored warm; diastase is a natural honey enzyme whose activity falls as heat load rises. The Honey (England) Regulations 2015 bound both: no more than 40 mg/kg of HMF (80 for honeys of declared tropical origin), and diastase activity of at least 8 on the Schade scale.
The honest detail: a properly run flash pasteurisation barely moves either marker — after it, in Bogdanov’s summary, diastase activity and HMF “remain almost unchanged”, while a more heat-sensitive enzyme, invertase, takes the damage. What drives honey towards the legal limits is slow, careless heat: long hours in a warm tank, or months of warm storage, which raise HMF in raw and pasteurised honey alike.
Fig. II · The heat a jar has takenDiagram
Heat load on both its axes — how hot, and for how long
Hydroxymethylfurfural (HMF) accumulates as honey is heated — or simply stored warm; diastase, a natural honey enzyme, falls in activity as heat load rises. Three exposures this page names, each with the verdict the page gives it.
Temperature — hottest at the top
The flash step — pasteurisation
70–78°Ca few seconds, then rapid cooling
Diastase activity and HMF “remain almost unchanged” — invertase, a more heat-sensitive enzyme, takes the damage.
Gentle bottling warmth
40–50°Ca day or two
A day or two does no damage.
Below this rule the temperature axis stops: this page gives no temperature for a warm tank or for warm storage, so none is drawn.
Slow, careless heat — long hours in a warm tank, or months of warm storage
temperature not statedlong hours to months
Raises HMF in raw and pasteurised honey alike — this is what drives honey towards the legal limits.
Time held — the page’s own steps, in order. The spacing is ordinal, not a measured scale.
Not drawn on this field
- No HMF or diastase value. This page reports no measurement for any exposure drawn here.
- Neither legal limit — no more than 40 mg/kg of HMF, and diastase activity of at least 8 on the Schade scale. Both are stated on this page, and both are left off: with nothing measured here, no exposure could honestly be shown approaching them.
- No aroma. This field is the two markers; what heat and warm storage do to a honey’s volatiles is the paragraph below, not a position on this grid.
- No shading for harm. A blended, pasteurised supermarket honey is honest food doing what is asked of it; this field places exposures, it does not grade jars.
The hot exposure is the smallest mark on the field. The one this page says drives honey towards the legal limits is the long warm one — and it raises HMF in raw and pasteurised honey alike.
Aroma is the change a buyer can actually taste. The volatile compounds that carry floral character diminish as heating runs hotter or longer — through to “a caramel like taste” in extreme cases — and warm storage alone costs a honey much of its aroma within a few months. Heat, in short, moves honey towards anonymity.
There is also a legal backstop: honey sold in the UK — baker’s honey aside — must not have been heated so far that its natural enzymes are destroyed or significantly inactivated. A UK jar labelled simply “honey” cannot lawfully have been cooked hard.
What does pasteurisation not change?
Almost everything else. Pasteurised honey is honey in law: the same reserved description, the same compositional schedule, the same rule that nothing may be added and nothing removed. The changes above are measured in milligrams per kilogram; the sugars that make up the bulk of the jar are the same before and after, and so is what the jar does in the kitchen — in tea, on yoghurt, in a glaze.
Safety does not divide the two jars either — with one line that applies to both. The NHS advises giving no honey to children under one year old, because honey occasionally contains bacteria that can produce toxins in a baby’s intestines, causing infant botulism. That advice covers honey of every processing level, and heating does not change it.
Why is supermarket honey pasteurised?
Because at packing scale, setting and fermentation are expensive problems. Honey bottled by the tonne must pour through pipes and fine filters, sit clear under shop lighting for months without setting, and never ferment in a warehouse that runs warm in summer. Flash pasteurisation and fine filtration deliver exactly that, at a trace-level cost the law bounds.
There is no snobbery worth having here. A blended, pasteurised supermarket honey is honest food doing what is asked of it — it sweetens tea, bakes and stirs into porridge, and it meets the same compositional floor as every other honey on the shelf. Processing is also a different question from authenticity: a pasteurised honey is not a fake honey, and the checks that catch real fraud are in how to tell if honey is real.
When does raw matter?
Three cases, all about what heat and fine filtration take away.
Floral character. The volatiles that make a thyme honey smell of thyme are precisely what heat and warm storage erode. A varietal honey is bought for its scent; raw handling protects the point of the purchase.
Evidence. Raw has no UK legal definition, so the word is only as good as the numbers behind it: low HMF and high diastase, measured and published per batch. The full standard is in what raw honey is.
Set behaviour. Unpasteurised honey sets on its floral source’s own schedule — fast for glucose-rich honeys, slowly or hardly at all for others — and can set fine; pasteurised honey sets late and coarse. If you care how a honey sets, raw is the version that shows it; the buying question is in set vs runny honey.
One removal sits alongside heat: the fine pressure filtration that often follows pasteurisation strips out pollen — and pollen is how a honey’s botanical and geographical origin is checked. That is why “filtered honey” is its own description in UK law.
The raw side of the shelf, from the top, starts at raw honey.
How can you tell which jar you are holding?
Not from the word “pasteurised”: UK labelling law does not require heat treatment to be declared. Read what the label must and may say instead:
- Country of origin must appear: the country where the honey was harvested — or, for honey blended from more than one country, a ‘blend of honeys…’ indication instead of a named country. Most supermarket blends carry the blend wording.
- “Raw” or “unpasteurised” are voluntary claims, credible when backed by per-batch HMF and diastase results rather than the word alone.
- “Filtered honey” is a reserved description meaning significant pollen removal — and a jar so described may not state a floral, regional or territorial origin.
- “Baker’s honey” must carry “intended for cooking only” beside the name; it is the one category exempt from the enzyme-inactivation rule.
The reading rule: producers who avoid the heat step say so, with numbers, because it is their point of difference. Silence is not proof, but it usually means conventional processing.
How do raw and pasteurised honey compare?
| Raw honey | Pasteurised honey | |
|---|---|---|
| The word describes | Handling: no pasteurisation, no fine filtration after extraction | A brief heat step: seconds at 70–78°C, then rapid cooling |
| Done for | Keeping the honey as it left the comb | Delayed set; no fermentation in higher-moisture honey |
| Legal category | None — honey, under the 2015 Regulations | None — the same standard, same HMF and diastase limits |
| Crystallisation | On the floral source’s schedule; can set fine | Delayed for months; slow and coarse when it comes |
| Aroma | Handling protects the volatiles | The flash step limits the loss; long heat and warm storage cost more |
| On the label | “Raw” or “unpasteurised”, ideally with per-batch results | Usually nothing — heat treatment need not be declared |
The blunt summary: the two jars differ in handling and in what can be proved about them, not in what they are. Neither deserves the other’s marketing.
Where THYMELIA stands
THYMELIA is a UK house of Greek foods working two harvests — raw thyme honey from Chania in western Crete, and early-harvest olive oil from the hills above Kalamata, and it will stand on both sides of this comparison deliberately: the range will include raw products and conventional ones, each labelled for exactly what it is. A jar sold as raw will carry the only backing the word can have — per-batch HMF and diastase results, published; a heat-processed product will say what it is, and will not borrow the word. There is no shop yet. How we source is at sourcing, what we will test and publish is at testing, and the research behind these products is at evidence, taken one study at a time.
Asked, answered.
Is pasteurised honey still real honey?
Yes. UK law sets one compositional standard for honey — the Honey (England) Regulations 2015 — and pasteurised honey must meet it in full: the same limits on moisture, HMF and diastase activity apply whether or not the jar was heated. There is no separate legal category for pasteurised honey, and no honey may be heated so far that its natural enzymes are destroyed or significantly inactivated. Baker's honey is the one exception, and must say so.
Why is honey pasteurised if not for safety?
Two commercial reasons. Flash heating dissolves the fine seed crystals that would otherwise start granulation, so the honey stays liquid and clear on the shelf for longer. It also destroys the yeasts naturally present in honey, which can ferment a honey whose water content runs high — a real risk above roughly 18 per cent water. Neither purpose has anything to do with making the honey safe to eat.
Does pasteurised honey crystallise?
Eventually, yes. Pasteurisation dissolves the seed crystals that begin granulation, so a pasteurised honey stays liquid considerably longer, but the sugars that drive crystallisation are still there. When it does set, it tends to do so slowly and in coarse crystals rather than a fine, even paste. Crystallisation itself is a physical behaviour of honey, not a fault, and it says nothing about quality on its own.
How can I tell if a UK honey is pasteurised?
Not from the word itself — UK labelling law does not require heat treatment to be declared, so most labels are silent. In practice the signal runs the other way: producers who do not pasteurise say so, because it is their point of difference. Look for raw or unpasteurised backed by published per-batch HMF and diastase results. Baker's honey, marked intended for cooking only, is the one category allowed to be heavily heated.
Is raw honey a legally defined term in the UK?
No. The Honey (England) Regulations 2015 define honey itself, plus descriptions such as filtered honey and baker's honey, but no raw category — the word is a voluntary handling claim. What UK law does set are limits heat pushes against: HMF no higher than 40 mg/kg and diastase activity of at least 8. A raw claim worth trusting therefore comes with those two numbers, measured and published for the batch in the jar.
Sources
- The Honey (England) Regulations 2015
- The Honey (England) Regulations 2015, Schedule 1 — compositional criteria
- Honey Technology — Stefan Bogdanov, The Book of Honey, Chapter 3, Bee Product Science
- Value-added products from beekeeping, Chapter 2 (Honey) — FAO, R. Krell
- Foods to avoid giving babies and young children — NHS