Why Is My Honey Bubbling? The Truth About Honey Fermentation and Spoilage

Introduction

You open your pantry to grab a spoonful of honey — and something is wrong. The jar is slightly bulging. There is white foam sitting on the surface. The honey looks like it is slowly, quietly, bubbling.

Honey is supposed to last forever. So what is happening?

This is one of the most common questions we receive at Kashmiril, and the answer is more fascinating than most people expect. Honey is not a dead, inert sweetener. It is a living biological system. And under the right (or wrong) conditions, it can ferment — meaning it can start to break down, produce gas, and change completely.

In this guide, we will walk you through exactly why honey bubbles, how to tell if yours has gone bad, whether fermented honey is dangerous, and how to store your honey so this never happens again.

What Actually Causes Honey to Ferment?

Most people assume honey never goes bad. They have heard the stories about ancient honey found in Egyptian tombs, still edible after thousands of years. But that honey was stored in perfect, sealed, dry conditions. Your kitchen pantry is a very different story.

Here is what is really happening inside that bubbling jar.

The Yeast You Never Knew Was There

All raw honey — including the finest wild-harvested Kashmiri honey — naturally contains dormant spores of osmophilic yeasts (pronounced oz-mo-FIL-ik; these are special yeast strains that can survive in extremely high-sugar environments). The most common type is Zygosaccharomyces rouxii. Bees pick up these spores while foraging on flowers and pollen, and they end up in the honey naturally.

In healthy, well-stored honey, these yeast spores simply sit there. They are dormant — like seeds that never get water. The honey's natural properties keep them completely inactive.

But when conditions change, these yeasts wake up.

The Chemical Reaction That Makes Honey Bubble

When osmophilic yeasts become active, they start feeding on the sugars in honey — specifically glucose and fructose, which are the two main sugars in all honey. As they digest these sugars, they produce two things:

• Ethanol (the same alcohol found in wine and beer)
• Carbon dioxide gas (CO₂ — the same gas in your fizzy drinks)

The CO₂ has nowhere to go in thick, viscous honey. It gets trapped, creating bubbles. Over time, you see white foam on the surface, active fizzing, and in some cases, so much pressure builds up that the lid pops off or the jar visibly bulges.

That fizzing jar? It is essentially a very slow, uncontrolled version of brewing.

In our experience handling raw Kashmiri honey sourced directly from wild-harvested batches in the Kashmir valley, we have seen this happen to honey that was exposed to even a small amount of moisture — sometimes just from a wet spoon being dipped into the jar. That small amount of water is all it takes.

If you want to understand more about what separates raw honey from its processed counterpart, our guide on raw honey vs. processed honey explains the full picture — including why raw honey is more prone to this, and why that is actually a sign of quality.

The 18.6% Rule — The Hidden Number That Controls Everything

Now here is the technical detail that most honey guides never tell you: moisture content is the single most important factor in whether honey ferments or stays stable.

Honey naturally has very low water content, which is one of the main reasons it does not spoil. The water content also creates something called osmotic pressure (the pulling force that draws water out of bacteria and microbes, essentially dehydrating and killing them before they can cause any harm).

But if the moisture level inside the honey rises above a certain threshold, that protection collapses — and fermentation begins.

The Three Risk Zones

The USDA (United States Department of Agriculture) sets the moisture limit for Grade A honey at 18.6% or below. Here is how the risk breaks down:

• Below 17.1% moisture: Highly stable. Fermentation is extremely unlikely regardless of how many yeast spores are present.
• 17.1% to 19% moisture: Moderate risk. Fermentation is possible, especially if the yeast spore count is high.
• Above 19% moisture: High risk. Spontaneous fermentation is very likely to begin.

Professional beekeepers use a precision tool called a refractometer (a handheld device that measures how light bends through a liquid to determine its water content) before bottling any honey. If moisture is too high, the honey is not yet "ripe" and should not be jarred.

This is also why our Kashmiri Honey Collection is sourced only from mature, fully-capped honeycomb — meaning the bees have already sealed the honey, confirming it has reached the right moisture level naturally.

Crystallization vs. Fermentation — A Crucial Difference

This is the single most common confusion we see, and it is important to get right.

When honey turns thick, grainy, or solid — that is crystallization, not fermentation. And crystallization is completely normal and natural.

Here is why it happens: Honey is a supersaturated solution (meaning it holds more dissolved sugar than water alone could normally hold). Over time, the glucose naturally separates from the water and forms solid crystals, while the fructose stays liquid. This is a physical change, not a chemical one. It does not affect the quality, taste, or safety of the honey at all.

In fact, crystallization is actually a sign of pure, raw honey. Highly processed or adulterated honey is treated to prevent crystallization, which removes many of its natural benefits.

Our guide on honey crystallization explains this fully.

How Crystallization Can Lead to Fermentation

Here is the connection most people do not know: crystallized honey is actually at a higher risk of fermenting than fresh liquid honey.

When glucose crystallizes, it pulls itself out of the honey mixture — but it leaves behind the water it was holding. This means the remaining liquid (mostly fructose) becomes more concentrated in water. The local water activity (a scientific measure of how available water is for chemical reactions and microbial growth) rises significantly in this watery upper layer.

That watery layer becomes the perfect environment for dormant yeast to wake up. This is why old, crystallized honey that has been sitting in a warm kitchen is particularly at risk.

How to Tell if Your Honey Has Actually Spoiled

Not every jar that looks different has gone bad. Here is a simple sensory checklist to help you diagnose your honey properly.

What True Fermentation Looks Like

Visually: Active bubbling or fizzing. White frothy foam on the surface, especially clustered at the top. Honey that appears separated or unusually cloudy in a way that is new.

By smell: A sharp, sour, yeasty aroma — like bread dough, beer, or vinegar. This smell is caused by the ethanol produced during fermentation being further converted to acetic acid (the compound that gives vinegar its sharp scent) by naturally occurring bacteria.

By taste: A sour, tangy, or bitter flavor that replaces the usual floral sweetness. If it tastes like something between wine and vinegar rather than honey, it has fermented.

What Is Not Spoilage

• Honey that has turned dark or amber over time — this is the Maillard reaction (a natural browning process caused by heat and time, the same reaction that browns bread when toasted), not fermentation. It is safe.
• Honey that is white and solid — this is just crystallization, as discussed above.
• Honey with a very mild, barely detectable fizz and no sour smell — this could be very early-stage fermentation or simply dissolved CO₂ from processing. Check the smell and taste to confirm.

For a deeper look at testing honey quality at home, our guide on how to identify pure honey walks you through simple tests you can do right in your kitchen.

Is Fermented Honey Safe to Eat?

Here is the honest answer: it depends on who is eating it.

For Healthy Adults

For most healthy adults, lightly fermented honey is not a toxicological (poison-related) hazard. The byproducts of fermentation — ethanol and acetic acid — are benign at the small concentrations found in accidentally fermented honey. You might find the taste unpleasant (sour and fizzy), but it will not harm you.

Technically, spontaneous fermentation is a quality defect — not a safety emergency for adults.

All honey naturally contains spores of Clostridium botulinum (a bacteria whose spores exist widely in soil and pollen). In adults and older children, these spores are harmless — the acidic environment of our gut keeps them permanently dormant. But infants under 12 months have not yet developed the gut acidity or protective microbiome needed to stop these spores from germinating. When the spores germinate, they produce botulinum toxin, one of the most potent toxins known. The result is infant botulism, a life-threatening condition.

This risk applies to all honey — not just fermented honey. But fermented honey, with its altered pH and structure, can be even more unpredictable. No honey, ever, for babies under 1 year old.

For a full breakdown of honey safety for children, read our dedicated guide on honey for kids — safe ages and daily limits.

The Pasteurization Myth You Need to Know

Many people assume that commercial pasteurization (heating honey to around 63–71°C / 145–160°F) makes it completely safe by killing everything inside. This is only partially true.

Pasteurization does kill active yeast cells, which is why commercially pasteurized honey is less likely to ferment. It also delays crystallization by dissolving glucose crystals. But pasteurization does not kill botulism spores. Destroying those spores requires pressure cooking at 121°C / 250°F, a temperature that would completely destroy the honey — its enzymes, its flavonoids, its colour, its aroma. Everything that makes honey valuable would be gone.

This means no honey product on the market can be certified botulism-free. The answer for adults is that it does not matter — our bodies handle it. The answer for infants remains unchanged: no honey, ever.

Intentional Fermentation — When Bubbles Are Actually a Good Thing

Fermentation is not always an accident. In fact, some of the most celebrated food traditions in the world are built entirely on deliberate honey fermentation.

Honey Fermented Garlic

This traditional health remedy involves submerging fresh garlic cloves in raw honey. The garlic — which is approximately 60% water — begins to release moisture into the honey through a process called osmosis (the movement of water from an area of lower concentration to higher concentration through a semi-permeable surface, like the cell walls of garlic). This dilutes the honey enough to trigger gentle fermentation.

The result is mellow, slightly tangy garlic infused with the sweetness and complexity of fermented honey. One safety note: raw garlic can raise the pH of honey (making it less acidic). To keep the environment safely acidic and prevent any risk, it is recommended to add a small splash of raw apple cider vinegar to keep the pH below 4.6.

Mead — The World's Oldest Fermented Drink

Mead is simply honey wine — created by diluting honey with water and adding specific yeast strains to produce a fermented, alcoholic beverage. Archaeological evidence suggests mead predates grape wine by thousands of years, making it arguably the oldest fermented drink in human history.

Honey in Baking and Sourdough

In bread-making, honey acts as "fast food" for yeast — providing a rapid source of easily digestible sugars that help the dough rise quickly. Honey also acts as a humectant (a substance that draws in and retains moisture from the surrounding environment), which is why bread made with honey stays soft longer than bread made with white sugar.

How to Store Honey Properly — And Stop Fermentation Before It Starts

Prevention is far easier than dealing with a fermented jar. Follow these evidence-based storage practices.

Use Airtight Glass Jars

Honey is hygroscopic (it actively absorbs moisture from the surrounding air). An open or loosely-sealed jar is absorbing moisture constantly. Glass is the best container because it does not leach any chemicals and maintains an airtight seal effectively. Always store your honey with the lid tightly secured.

Room Temperature Is Ideal

Store honey between 20–25°C (68–77°F). This is the sweet spot — warm enough that crystallization is slow, but not so warm that it encourages microbial growth.

Do not refrigerate honey. Cold temperatures between 10–15°C (50–60°F) dramatically accelerate crystallization. As we covered earlier, crystallized honey is more vulnerable to fermentation. The refrigerator also introduces humidity, which raises the moisture content of your honey over time.

The Freezer Is Your Emergency Option

If you have honey with a known high moisture content — for example, a raw batch that was harvested early or has a noticeably thin consistency — you can freeze it. Freezing stops all microbial activity completely without damaging the enzymes, pollen, or antioxidants in the honey. When you defrost it slowly at room temperature, it will be exactly as it was.

For a complete, science-backed storage guide, read our dedicated article on how to store honey and keep it fresh for decades.

Frequently Asked Questions