Yes, honey naturally contains yeast. Even high-quality, properly harvested honey typically carries small numbers of yeast cells, usually fewer than 100 colony-forming units per gram. These yeasts enter honey through flowers, the bees themselves, and the surrounding environment. In most cases, they remain dormant and pose no risk to you, but under certain conditions they can wake up and cause honey to ferment.
How Yeast Gets Into Honey
Yeast is everywhere in nature: in soil, in the air, and on the surfaces of plants. Flower nectar, which bees collect to make honey, is a sugar-rich environment that naturally attracts yeast. Several yeast genera, including Aureobasidium, Metschnikowia, and Meyerozyma, have been found living in flowers, inside the digestive tracts of bees, and in finished bee products. This creates a continuous loop where yeasts cycle between flowers and bees during foraging.
Bees also carry yeast in their gut as part of their normal microbiome. Some of these yeasts play a useful role in the hive, actively helping convert pollen into “bee bread,” a fermented food product that bee colonies depend on for development. So yeast isn’t a contaminant in the traditional sense. It’s a natural part of the ecosystem that produces honey.
Types of Yeast Found in Honey
The most commonly identified yeasts in honey belong to the genus Saccharomyces (the same broad family used in bread and beer making) along with Candida, Torulopsis, and others. One particularly interesting species, Saccharomyces bisporus var. mellis, is an obligate osmophilic yeast, meaning it actually requires high sugar concentrations (10 to 20% glucose) to grow at all. It’s essentially a specialist adapted to honey’s extreme sugar environment.
A study of Polish artisanal honeys found 15 wild-type yeast strains across species like Candida magnoliae, Yarrowia lipolytica, and Starmerella magnoliae. Nectar honeys tend to have more yeast species, while honeydew honeys are more commonly colonized by mold fungi. In the vast majority of samples tested (81% in one study of 21 honeys), the total fungal count was fewer than 10 colony-forming units per gram, an extremely low number.
Why Yeast Usually Stays Dormant
Honey is one of the most inhospitable environments for microbial growth. Its moisture content typically sits below 18%, which is far too dry for most microorganisms to thrive. Honey is also highly acidic and contains naturally occurring hydrogen peroxide, all of which suppress microbial activity. The small number of yeast cells present in properly stored honey remain dormant under these conditions, essentially alive but unable to reproduce or ferment.
This is why honey has such a remarkable shelf life. Archaeological finds of honey thousands of years old have shown no signs of spoilage. The yeast is there, but it can’t do anything.
When Yeast Becomes a Problem
The critical factor is moisture. Honey with a moisture content above 19% creates conditions where dormant yeast can activate and begin fermenting the sugars in honey. This produces alcohol and carbon dioxide, giving the honey a sour or “off” taste, a fizzy texture, and sometimes visible bubbling.
Several things can push moisture levels into that danger zone. Harvesting honey before bees have fully capped the comb (meaning the bees haven’t finished dehydrating it) is the most common cause. Storing honey in humid environments or leaving containers unsealed can also allow the honey to absorb moisture from the air. Temperature matters too: yeast in honey grows actively between 10°C and 27°C (50°F to 80°F). Below 10°C, fermentation stops, though it will resume once the honey warms up again.
The starting yeast count also matters. While most fresh honeys contain fewer than 100 yeast cells per gram, that number can climb dramatically during storage if conditions allow even modest growth. A study of artisanal honeys noted that initial low yeast levels can increase significantly over time, especially when moisture is borderline.
Raw Honey vs. Pasteurized Honey
Raw honey retains its natural yeast population along with enzymes, antioxidants, and other beneficial compounds. For most people eating most honey, this is perfectly fine. The yeast counts are too low to cause any digestive issues or health concerns.
Commercial honey is often pasteurized at around 78°C (172°F) for six minutes, which effectively kills yeast and mold. This reduces the risk of fermentation during storage and extends shelf stability, which is why store-bought honey rarely ferments even after sitting in a pantry for years. The tradeoff is that pasteurization also reduces some of honey’s natural antioxidant activity and alters its physicochemical properties. A gentler heat treatment at 55°C for 15 minutes has been tested as a compromise, though it’s less effective at eliminating microorganisms.
After pasteurization, yeast and mold counts drop significantly. Over six months of storage, pasteurized honey reaches near-total inactivation of remaining organisms.
Is Fermented Honey Safe to Eat?
Honey that has fermented isn’t dangerous in the way spoiled meat or dairy would be. The fermentation is driven by the same types of yeast used in winemaking and baking. Many people intentionally ferment honey to make mead (honey wine) or use fermented honey as an ingredient. The taste changes considerably, becoming more acidic and sometimes alcoholic, which is why most people consider unintentionally fermented honey to be spoiled rather than improved.
If your honey smells sour, looks foamy on top, or has a slightly alcoholic tang, fermentation has likely started. You can still use it in cooking or baking where the off-flavors won’t be as noticeable. Refrigerating it below 10°C will halt further fermentation, though it won’t reverse the flavor changes that have already occurred.
How to Keep Yeast From Fermenting Your Honey
Proper storage is the simplest defense. Keep honey in a tightly sealed container in a cool, dry place. If you live in a humid climate or your honey came from a local beekeeper who may have harvested it at slightly higher moisture levels, storing it in the refrigerator provides extra insurance. The cold won’t harm the honey, and it keeps yeast completely inactive.
If you’re a beekeeper, the most reliable step is ensuring honey reaches a moisture content below 18% before extraction. A refractometer, an inexpensive tool that measures sugar concentration, can confirm whether your honey is in the safe range. Honey between 18% and 19% moisture is a gray area where fermentation is possible but not guaranteed, especially if yeast counts happen to be higher than average.