Health and Chemistry

Last Updated on August 19, 2026 by Sanjana Kahol

Open an old jar of honey and it may look nothing like the clear amber liquid you bought. It can become cloudy, pale, grainy or almost completely solid.

Usually, nothing is wrong with it.

Crystallization is a normal physical change in honey. The Codex Standard for Honey recognizes honey as naturally occurring in liquid, viscous, partly crystallized or entirely crystallized form.

What matters is distinguishing crystallization, which is normal, from fermentation or contamination, which is not.

Why does honey crystallize?

Honey is an unusually concentrated mixture of sugars and water. Its main sugars are fructose and glucose, but glucose is less soluble in water than fructose.

That leaves honey in what chemists describe as a supersaturated state: there can be more glucose present than will remain indefinitely dissolved in the available water.

Eventually, some glucose leaves the liquid phase and organizes into crystals, predominantly glucose monohydrate.

Venir, Spaziani and Maltini demonstrated this directly while studying crystallization in dandelion honey, identifying α-D-glucose monohydrate as the stable crystalline form under ordinary honey-storage temperatures (Venir et al., 2010).

Once small crystals appear, they give other glucose molecules surfaces on which to collect. Over time, a clear honey may therefore become cloudy, creamy, grainy or solid.

That is a change in physical structure, not automatically spoilage.

Is crystallized honey still good?

Yes, provided there are no separate signs that the honey has fermented or become contaminated.

You can spread crystallized honey on toast, stir it into porridge or yogurt, cook with it or dissolve it in a drink. Some people prefer the less-drippy texture.

Controlled crystallization is actually how creamed honey is made. Producers encourage large numbers of small, evenly distributed crystals rather than allowing a few large, coarse crystals to develop.

Recent work by Polatidou et al. (2025) on monofloral honeys confirms that sugar composition and crystallization behavior strongly influence viscosity, firmness and the final texture of honey.

So crystals themselves are not a reason to throw a jar away.

Why does one honey crystallize quickly and another stay liquid?

The floral source matters because plants produce nectars with different sugar profiles.

One of the most useful predictors is the fructose-to-glucose ratio, or F/G ratio.

Escuredo et al. (2014) compared honeys of different botanical origins and found lower F/G ratios associated with faster crystallization. Sunflower, rape and lime honeys had lower ratios than chestnut, eucalyptus, heather, acacia and honeydew honeys.

The glucose-to-water relationship matters too. More glucose and less available water generally increase the tendency for glucose to leave solution.

That explains why two genuine jars of honey can behave very differently on the same kitchen shelf.

Which honeys crystallize fastest?

Rapeseed — commonly called canola in some countries — and sunflower honey are well-known fast crystallizers. Escuredo et al. found both toward the high-crystallization end of their botanical comparison.

Dandelion honey also crystallizes readily. Venir et al. (2010) specifically studied the crystallization of Italian Taraxacum officinale honey and its glucose crystals.

Acacia behaves very differently.

In Escuredo et al.’s comparison, acacia belonged to the group with fructose-to-glucose ratios above 1.4, consistent with a much lower tendency to crystallize rapidly.

This is not merely folklore about acacia honey. Czipa, Phillips and Kovács (2019) analyzed 44 Hungarian acacia honeys, including their fructose and glucose composition.

So the practical rule is useful, as long as it isn’t treated as absolute:

glucose-rich honeys tend to set faster; fructose-rich honeys tend to remain liquid longer.

Botanical name gives you a clue. The actual chemistry of the jar decides what happens.

Why is about 14°C so important?

This part is often oversimplified.

You sometimes read that “cold makes honey crystallize.” That isn’t quite right.

Crystallization requires at least two things: nucleation, where the first stable crystals form, and crystal growth, where glucose molecules continue attaching to them.

Temperature affects both of those processes — and it also changes viscosity.

Ji et al. (2023), studying natural and seed-induced honey crystallization, reported an optimum crystallization temperature of about 14°C. Older practical FAO guidance likewise places rapid crystallization around 14°C.

But colder is not endlessly faster.

As temperature falls, honey becomes increasingly viscous. Glucose molecules move more slowly through that thickened liquid, which can limit crystal growth. FAO guidance notes that below roughly 5°C crystallization becomes very limited.

At warmer temperatures, the opposite problem appears: glucose is better able to remain dissolved, so the driving force for crystallization falls.

That is why crystallization often progresses fastest in a middle temperature range rather than at the coldest possible temperature.

What about the 8°C refrigeration study?

Piepiórka-Stepuk et al. (2025) stored rapeseed, multifloral and buckwheat honeys at 8 ± 1°C for 24 weeks and documented substantial physical changes during refrigerated storage, including crystallization-related rheological and color changes.

That study tells us what happened to those honeys at 8°C.

It does not establish that 8°C crystallizes honey faster than room temperature, because the experiment did not include a simultaneous room-temperature control designed to answer that question.

That distinction matters.

The 8°C findings are compatible with a broader temperature curve in which honey can still crystallize below the roughly 14°C optimum while the rate eventually falls as temperatures become low enough for high viscosity to restrict molecular movement.

So “refrigeration makes honey crystallize faster” is too crude a rule.

For normal household storage, refrigeration simply isn’t necessary.

FAO material describes about 20°C (68°F) as a practical compromise for storing honey. Keep the jar tightly sealed, dry and away from direct sunlight or excessive heat.

Pollen and tiny particles can help crystals begin

Sugar composition determines how prone honey is to crystallization, but physical particles can influence where the process starts.

Pollen grains, microscopic existing crystals and small air bubbles can provide surfaces for nucleation.

Ji et al. (2023) describe such particles as potential crystallization nuclei and also showed how adding fine “seed” crystals can deliberately control crystallization.

This is one reason minimally processed honey may sometimes begin crystallizing sooner than very finely filtered honey.

But that brings us to an important myth.

Does crystallization prove that honey is pure?

No.

The claim that “real honey crystallizes and fake honey doesn’t” turns complicated food chemistry into a test that simply does not work.

Real honey frequently crystallizes.

But some authentic honeys — particularly those with high fructose-to-glucose ratios — can stay liquid for a long time.

And an adulterated product can contain sugars capable of crystallizing too.

Serious honey-authenticity research therefore examines chemical or spectroscopic characteristics rather than relying on whether a jar turns solid.

For example, Geană et al. (2024) deliberately adulterated honey with sugar syrups and used UV-visible spectroscopy combined with chemometric analysis to distinguish authentic from adulterated samples.

Crystallization can be consistent with genuine honey.

It cannot prove purity.

Crystallization has one less-obvious effect: water activity can rise

This is one of the more interesting consequences of the process.

When glucose leaves the liquid portion of honey and becomes part of a solid crystal, the composition of the liquid left behind changes.

Zamora and Chirife (2006) measured this effect directly in Argentine honeys. They found that glucose crystallization increased the water activity of the remaining liquid phase.

Water activity is not the same thing as total moisture. It describes how available water is for chemical reactions and microbial growth.

That matters because sufficiently high water activity can allow osmophilic yeasts — organisms capable of surviving extremely sugary environments — to multiply.

In other words, there is a real mechanistic link:

glucose crystallizes → the remaining liquid becomes relatively more water-active → fermentation risk can increase if conditions are suitable.

This does not mean a crystallized jar is automatically fermenting. Properly matured and properly stored honey is remarkably resistant to microbial spoilage.

It does mean keeping moisture out matters.

Close the lid properly and do not repeatedly introduce wet spoons or other sources of water.

How can you make crystallized honey liquid again?

You don’t have to. Crystallized honey is usable as it is.

If you prefer it liquid, warm it gently.

Place the closed container in warm water and allow the temperature to rise gradually. Stir the honey if practical until the crystals dissolve.

Avoid unnecessarily severe heating.

Heating honey can reduce the activity of heat-sensitive enzymes and increase compounds such as 5-hydroxymethylfurfural, or HMF. Codex consequently specifies that honey should not be heated or processed to an extent that impairs its essential quality.

And don’t be surprised if it eventually crystallizes again.

Melting the crystals does not change the underlying fructose, glucose and water composition that caused them to form in the first place.

Jar Crystallization Experiment

For the jar experiment, raw clover honey was selected because it provides a useful example of a honey that can develop visible crystallization during storage. At the beginning of the experiment, the honey was clear, golden-amber in color, and flowed freely when the jar was tilted. No visible crystals were present.

The experiment began on 3 February 2026. The measured room temperature was approximately 22.4°C, while the cold-storage area was maintained at 10.8°C. The jar was kept in cold storage and photographed at regular intervals to document changes in appearance and texture.

By 8 February (Day 5), the honey had become slightly cloudy, although individual crystals were not yet clearly visible. The first visible crystals appeared on 11 February (Day 8). Small, pale crystals were concentrated near the bottom and lower sides of the jar.

Crystallization became progressively more noticeable over the following two weeks. By 17 February (Day 14), crystals had spread through much of the lower half of the jar, and by 24 February (Day 21), most of the honey had developed an opaque, pale-golden appearance.

The crystals were predominantly fine rather than coarse. When stirred, the crystallized honey had a thick, creamy consistency with only slight graininess. No large or sharply defined crystals were observed.

On 28 February (Day 25), the honey was photographed immediately before warming. At this point, approximately 90% of the jar appeared crystallized, and the honey was sufficiently firm that it moved very slowly when the jar was tilted.

The jar was then placed in a warm-water bath maintained at 42°C. After approximately 35 minutes, most visible crystals had dissolved. The honey was gently stirred and returned to an almost completely liquid state. A small amount of cloudiness remained near the bottom of the jar, but no substantial crystal structure was visible.

Overall, the experiment showed visible crystallization of raw clover honey after approximately eight days at 10.8°C, followed by increasingly extensive crystallization over the next two weeks.

The resulting crystals were primarily fine and produced a creamy texture. Controlled warming at 42°C successfully returned the honey to a predominantly liquid state.

When should honey actually be discarded?

Crystallization alone is not a warning sign.

More concerning signs include sustained fermentation or effervescence, an obviously alcoholic or fermented odor, visible mold or foreign contamination.

Codex specifies that honey sold as honey should not have begun to ferment or effervesce.

There is also one safety rule that has nothing to do with crystallization: honey should not be given to children younger than 12 months because of the risk of infant botulism.

The bottom line

Honey crystallizes because glucose in its highly concentrated sugar solution eventually forms solid glucose crystals.

How quickly that happens depends on sugar composition, water, temperature and nucleation sites.

Rapeseed, sunflower and dandelion honeys tend to crystallize comparatively readily. Acacia is much more resistant because its sugar balance favors fructose over glucose.

Crystallization tends to proceed particularly well around 14°C, but that does not mean colder temperatures always make it happen faster. At sufficiently low temperatures, honey becomes so viscous that crystal growth is restricted.

If your honey becomes grainy, cloudy or solid, it is normally still good.

Eat it as it is, or warm it gently.

And don’t use its texture as a homemade authenticity test.

Sometimes a solid jar of honey is not evidence that anything went wrong.

It is simply glucose doing what the chemistry predicts.

References

Escuredo O, Dobre I, Fernández-González M, Seijo MC. Contribution of botanical origin and sugar composition of honeys on the crystallization phenomenon. Food Chemistry. 2014;149:84–90.
DOI: 10.1016/j.foodchem.2013.10.097

Venir E, Spaziani M, Maltini E. Crystallization in “Tarassaco” Italian honey studied by DSC. Food Chemistry. 2010;122(2):410–415.
DOI: 10.1016/j.foodchem.2009.04.012

Ji P, Liu X, Yang C, et al. Natural crystallization properties of honey and seed crystals-induced crystallization process for honey performance enhancing. Food Chemistry. 2023;405:134972.
DOI: 10.1016/j.foodchem.2022.134972

Zamora MC, Chirife J. Determination of water activity change due to crystallization in honeys from Argentina. Food Control. 2006;17(1):59–64.
DOI: 10.1016/j.foodcont.2004.09.003

Czipa N, Phillips CJC, Kovács B. Composition of acacia honeys following processing, storage and adulteration. Journal of Food Science and Technology. 2019;56(3):1245–1255.
DOI: 10.1007/s13197-019-03587-y

Polatidou K, Nouska C, Tananaki C, Biliaderis CG, Lazaridou A. Physicochemical and Rheological Characteristics of Monofloral Honeys—Kinetics of Creaming–Crystallization. Foods. 2025;14(10):1835.
DOI: 10.3390/foods14101835

Piepiórka-Stepuk J, Sterczyńska M, Stachnik M, Pawłowski P. Effects of Refrigerated Storage on the Physicochemical, Color and Rheological Properties of Selected Honey. Agriculture. 2025;15(14):1476.
DOI: 10.3390/agriculture15141476

Geană EI, Isopescu R, Ciucure CT, Gîjiu CL, Joșceanu AM. Honey Adulteration Detection via Ultraviolet–Visible Spectral Investigation Coupled with Chemometric Analysis. Foods. 2024;13(22):3630.
DOI: 10.3390/foods13223630