Honey Fermentation

About honey crystallizing:

92% of honey is composed of levulose (also referred to as Fructose), dextrose (also referred to as glucose) and water. The ratio of levulose, dextrose, water and the remaining other 8% of various sugars etc. is different for each source of nectar. This is why each honey has a unique flavor, aroma, body and color.

Nectar is mostly water, much of which is evaporated by the bees in the curing process of the honey. As the honey cures it becomes a supersaturated sugar solution. This means that the solution contains more sugar than would naturally dissolve into water at that temperature. Even if the honey is not supersaturated at the hive temperature of 95 degrees, it becomes supersaturated when it is cooled to room temperature. This is because sugar is more soluble in warmer water than in cooler water. Dextrose is less soluble than levulose and has a strong tendency to precipitate (form crystals) from a supersaturated solution.

Honey crystallizing is the process of dextrose reverting from a dissolved solution form into a solid crystal form. Some honey, such as mustard honey, has a higher percentage of dextrose and will crystallize very quickly. Some honey, such as sage honey, has a higher percentage of levulose and will crystallize very slowly. Honey does not spontaneously crystallize; the crystals must grow on a seed surface. This is why commercial packing plants filter honey, removing any small particles from the honey, eliminating many of the seeds upon which the crystals may grow. Heating honey also dissolves any microscopic crystals that are too small to be seen, removing them as seed surfaces.

Raw honey has an abundance of seed surfaces as it is loaded with pollen, microscopic dextrose crystals, and bits of wax and propolis. It will crystallize relatively quickly as compared to commercially heated and filtered honey. If crystallized honey is warmed, the dextrose becomes more soluble and will return to solution, that is why heating crystallized honey will return it to its liquid state. You can’t just heat it to the hive temperature of 95 degrees and expect all of the sugar crystals to return to solution though, because the honey was supersaturated at that temperature. The honey must be warm to a higher temperature to where the water will naturally dissolve all the available sugar. That is why I warm the honey to 115 degrees and not just 95 degrees when I re-liquify it. I am unwilling to warm honey beyond 115 degrees and still call it raw. Some honeys will not fully return to solution at 115 degrees and there will be a thin layer of crystallized dextrose in the bottom of the jar. Once re-liquefied the honey generally remains in the liquid state for a month and a half or more if stored at 70 degrees. If stored in the freezer the honey will remain in the liquid state for many months. It will re-crystallize very quickly if stored between 55 to 60 degrees.

Doesn’t honey keep forever? Why bother to re-liquefy honey?

Sadly the answers to the first question is no. Contrary to the popular belief that honey keeps forever; moisture makes it prone to spoilage just like any other food product. Water is the one common, necessary component for all living things on earth. Honey is hygroscopic, that means that it will attract and hold water molecules from the surrounding environment. Honey absorbs moisture from organism within it, if the honey has a low moisture content it will absorb so much water as to result in the organism’s death or at least prevent it from multiplying. This is one of the ways that it acts as an antibacterial agent. If the moisture content of honey is below 17.1 percent, even sugar tolerant yeasts are inactivated so the honey is safe from the possibility of fermentation. Unfortunately the yeast is not killed and if the honey is raw the yeast may become active if the moisture content rises sufficiently.

92% of honey is composed of dextrose, levulose and water with the remaining 8% being other sugars and the various components that give each honey its unique flavor. Crystallization will occur in almost all honey over time as the less soluble dextrose leaves solution and forms dextrose crystals. As dextrose leaves the solution, the ratio of water to the remaining sugars in solution increases. When enough dextrose has left the solution the moisture content of the solution will become more favorable to the yeast and fermentation becomes possible. The ways to prevent fermentation when this occurs is to either store the honey below 50 degrees, at temperatures low enough to inactivate the yeast, or to re-liquefy the honey so that the moisture/sugar ratio returns to a moisture content below 17.1 percent thereby inactivating the yeast.

Commercial honey packers prevent fermentation through pasteurization, heating the honey to 160 degrees killing the yeast. I believe that the high heat necessary to pasteurize the honey may destroy much of what is good in the honey and that it is better to keep it raw. I have found that warming honey to 115 degrees for several hours is enough to get most of the dextrose to return to solution, stop fermentation and preserve the good qualities of the honey.

Some people believe that if the honey is warmed at all it is not raw. This may be technically true but honey in the hives of the California central valley and desert region experiences temperatures of 115 degrees while still in the hive. It is preferred to eat raw honey just as it is when comes from the comb, if it crystallizes the risk of fermentation increases dramatically and can readily be observed. When fermentation is beginning or is likely to begin, it is far better to warm the honey and re-liquefy it to stop and prevent fermentation, and preserve the good qualities of the honey, rather than losing the honey altogether to fermentation. Any and all of my honey that has been warmed are clearly labeled with a label saying “This Honey has been warmed to 115 degrees F to re-liquify”. If there is no such label then it has not been warmed. I estimate that about 80% of my honey gets warmed before being sold. I consider the warmed honey to be raw, but if you do not then avoid the bottles that indicate that they have been warmed.

About Fermentation and Honey:

The main causes of honey spoilage are fermentation and heat. Fermentation is the production of ethyl alcohol and carbon dioxide by yeast as it grows and feeds on sugar. The ethyl alcohol may then break down into acetic acid (vinegar) and water in the presents of oxygen. The combined flavors of yeast, alcohol and acetic acid make the honey unpalatable. A number of physical changes also occur within the honey changing its physical characteristics as it ferments.

The yeasts responsible for fermentation are endemic throughout our environment. They are present in all honey that has not been pasteurized. The risk of fermentation is dependent on the moisture content and yeast spore concentration within the honey and on the temperature at which the honey is stored. According to US agriculture handbook number 335 Beekeeping In The United States

“Honey with less than 17.1 percent water will not ferment in a year, irrespective of the yeast count. Between 17.1 and 18 percent moisture, honey with 1000 yeast spores or less per gram will be safe for a year. When moisture is between 18.1 and 19 percent, not more than 10 yeast spores per gram can be present for safe storage. Above 19 percent water, honey can be expected to ferment even with only one spore per gram of honey, a level so low as to be very rare.”

“If honey has more than 17 percent moisture and contains a sufficient number of yeast spores, it will ferment. Such honey should be pasteurized, that is, heated sufficiently to kill such organisms.”

Since fermentation is also dependent on temperature it is assumed that the above quotes are for storage at room temperature. Moist honey will not ferment when stored below 50 degrees F or above 80 degrees F. Storing honey at temperatures above 80 degrees F to prevent fermentation is not recommended, the high temperature will damage honey in other ways that are equally objectionable. I recommend that consumers store their honey at room temperature if it will be consumed within 3 months. If your container of honey is too large to be consumed within three months then it should be divided into smaller containers and those that are not in use should be stored in the freezer or refrigerator, only the container of honey in use should be stored at room temperature.

Honey is extremely hygroscopic, that means that it will attract and hold water molecules from the surrounding environment. If it is left unsealed it will absorb moisture from the air and start to ferment at the top surface of the honey. This is not as easily identified as in crystallized honey so make sure you keep you honey jar sealed.

US grade A honey has a moisture content of not more than 18.6%. Yeast cannot grow unless the moisture content is above 17.1% and grows poorly between 17 and 18.5 percent, depending on the number of yeast spores present. What this means to the consumer is that Raw (not pasteurized) US Grade A honey with a moisture content of greater than 17% will likely keep for several months at room temperature without any adverse spoilage due to fermentation, longer periods of storage at room temperature may result in spoilage. When stored at temperatures less than 50 degrees Fahrenheit yeast cannot grow, so fermentation cannot occur and raw honey will keep for many months or years. My honey typically has a moisture content between 16 and 17.5 percent so it is generally safe from fermentation as long as it is not crystallized.

The relative moisture content in stored honey can increase in one of two ways. Either moisture is added to the honey by being absorbed from the environment or some sugar is removed from the honey sugar solution through crystallization. Crystallization is the process of dextrose leaving solution to form solid crystals and causes the relative moisture content of the remaining sugar solution to increase.

Raw honey tastes better than, and is much better for you than conventional commercially packaged honey. Unfortunately raw honey is also much more susceptible to fermentation than conventional commercially packaged honey. That is because commercially packaged honey that is not raw, has been pasteurized to kill the yeast, and has been filtered to remove most seed material that aids crystallization.

Much of the raw honey available from large-scale suppliers is from desert areas where it is very hot and dry. Honey from these regions can have a very low moisture content. Even after crystallizing the remaining sugar solution moisture content in desert honey may be low enough to prevent fermentation. If you want a long keeping raw honey with less likelihood of fermentation, shop for honey from a desert area.

Raw honey from cool, moist, foggy areas like the Monterey Bay area has a higher moisture content than desert source honey. It is particularly susceptible to fermentation when it has crystallized. If you live in the central coast area of Monterey Bay, want all the benefits of raw local honey, with a marvelously delicious taste that you can find no where else, then buy from a local beekeeper that produces raw honey and learn how to identify the signs of, and how to stop, fermentation of honey.

There is absolutely nothing wrong with crystallized honey. Many of us that like raw honey, like it better when it is crystallized. Creamed, spun, and whipped honey, are all names for crystallized honey with crystals so small that it has butter like texture. Don’t stress when your honey crystallizes you might even like it better that way. What you do need to do is learn to know the signs of fermentation and stop it before the honey is spoiled.

You can greatly retard the crystallization process by placing honey in the refrigerator of freezer. This makes the honey so thick that it is hard for the dextrose molecules to move to a crystal and leave the solution. Storing the honey below 50 degrees F also has the benefit of preventing fermentation during the period of storage by inactivating the yeast. Unfortunately it also makes the honey so thick that it is very hard to use. I recommend keeping your honey in the freezer if you have a jar that you are not going to open for a while.

You can minimize the chance that fermentation will occur by re-liquefying the honey whenever there are signs of crystallization, this will minimize the moisture content by maximizing the amount of sugar dissolved in the water. Keep in mind that over heating the honey or heating it for long periods of time will degrade the taste and the beneficial aspects of raw honey. To maintain the most benefit of the honey it must be warmed is little as possible for as sort a time as necessary. See How To Re-liquefy Crystallized Honey

Know the signs of fermentation:

Looking at fermentation from the bottom of the jar.

Looking at fermentation from the bottom of the jar.

Looking at the fermentation from the top of the jar.

Looking at the fermentation from the top of the jar.

As yeast grows it produces carbon dioxide gas. The carbon dioxide gas forms bubbles that push the sugar solution away from the dextrose sugar crystals making them visible. The sugar crystals will appear as light areas in the crystallized honey, forming feathery fractal like patterns. The longer it ferments the larger these light regions will grow.

In the top photo to the left we are looking through the bottom of a jar of honey that has been allowed to ferment to the point that it has changed the flavor of the honey. In the bottom photo to the right we are looking into the honey through the top of the same jar. The areas of fermentation are obvious by the light colored areas that the carbon dioxide bubbles cause.

Foam on top of  re-liquified/fermented honey

Foam on top of re-liquified/fermented honey

Don’t allow fermentation to get as far along as that shown in the pictures or the honey flavor will be greatly degraded in my opinion (then again I know some people that like the taste of it in this state). The skill to learn is how to identify the gas bubbles and re-liquefy the honey before the fermentation goes on too long. When you see any signs if fermentation the honey should be re-liquefied as soon as possible. The moisture content of the sugar solution will again be returned to that that it was before the crystallization occurred, If that was below 17.1% then the fermentation will stop. When you have had to re-liquefy a jar of honey to stop it from fermenting, then you know that that particular jar of honey will ferment when crystallized and it should be used as soon as possible, re-liquefied whenever it is showing signs of crystallizing or simply be stored (below 50 degrees) in the freezer or refrigerator to prevent fermentation and slow crystallization.

If you suspect that the honey might be fermenting but are not sure, re-liquefy the honey. If there is any foam on top of the honey after it is liquefied then it was fermenting. The foam is caused by the carbon dioxide bubbles as they are released from the crystallized honey. The photo above is of the same jar on the left after it is re-liquefied. As you can see by all the foam and the bubbles in the honey, the honey is badly fermented.

Honey does not have to crystallize to ferment. Liquid honey that is above 17.1 % moisture can and will ferment given enough time. If the moisture content is 18 % to 17.1 % then the honey will likely take a year or more before it ferments to the point it becomes a problem. Below 17.1% of moisture it will not ferment. If it is over 18.5 % water the fermentation can occur within a few months to the point that the carbon dioxide gas may blow the lid off the jar or break the jar. A full jar will bubble over as if boiling in very slow motion as the CO2 bubbles out of the honey, This is generally a sign that the honey was harvested too green and was definitely not  grade A honey, as grade A honey must be less than 18.6 % water. It seems odd to me that the grade A maximum moisture content was set at 18.6% instead of of 17.1% since honey with greater than 17.1% moisture can ferment. But then again when the standards were set I think most of the honey was pasteurized and filtered specifically to prevent it from fermenting. Also I have read that the ideal moisture content for ease of use is 17.5% and some packers often blend moist and dry honey to try and achieve this moisture level so the honey is not too thick and not too thin. Then of course they pasteurize it.

Below are additional pictures of fermenting honey that I came across in a health food store. Look carefully at crystallized honey that you are about to purchase to check for signs of fermentation before you buy it.

Evidence of fermentation. Don't buy this one.

Evidence of fermentation. Don’t buy this one.

Fermenting deep in the honey

Fermenting deep in the honey

How To Re-liquefy Crystalized Honey:

A comment about honey jars: In my opinion you should not heat any plastic container as some of the plastic chemicals can migrate into the food when it is heated. If the honey jar is not glass I do not recommend that you try to re-liquefy it until it is scoped out and placed into a glass jar first. This  is one of the main reasons that all my honey is bottled into glass jars. Glass may not be as convenient as squeeze bottles but the honey can be re-liquefied directly in the jar.

The most common way to re-liquefy honey is to remove the lid of the jar and place it in a deep pan of hot water. The hot water will heat the jar which heats the honey. Don’t boil the water, unless you are going to let the honey get to 160 degrees to kill all the yeast to prevent the possibility of future fermentation. Typically you just need to keep the water hot. Stir the honey occasionally to evenly distribute the heat throughout the honey. The cooler the hot water is the longer it will take to re-liquefy. The warmer the water, the faster it will re-liquefy. The hotter the honey is heated and the longer it is heated the more likely that some of the delicate flavors of the honey will be lost. In reality, many people will not notice the loss of the delicate flavors but I do, I am a bit of a honey snob, kind of like some wine connoisseurs. As soon as the honey is clear remove it from the hot water and let it cool. If it is runny but cloudy then it still has fine crystals in it. If you remove it from the water while it is cloudy then it will crystallize very quickly again.

The microwave method is an alternative quicker way to re-liquefy the honey. It is not a good method for large jars. It is much less controlled, and the honey will probably get hotter than the hot water method. The advantage is that it heats very quickly and then the jar can be placed in cool water bath to quickly cool it so the overall impact on the honey may be the same or less then the hot water method.  Remove the jar lid and place it in the micro wave. Heat it for 20 seconds and then stir it, if it is soft enough. Repeat with the heat stir cycle until the honey gets clear. Each microwave is different, you may find that it works better to heat it more or less than 20 seconds each heat cycle. The microwave only heats the honey on the outside so it needs to be stirred to distribute the heat throughout the honey. If you heat it too long then the outside honey will start to boil and the inside honey won’t be hot at all. You might as well take the temperature of the honey once it is clear and if it is near 160 degrees then you might as well heat it to 160 and pasteurize, now it can’t ferment because you just killed all the yeast. If it is far below 160 then I would just leave it and keep the delicate flavors. Now put the jar into a bath of cool water to rapidly cool the honey and preserve the delicate flavors as much as possible.