Honey Fermentation

A word of caution: Be careful of what you read and believe from the internet as most of it is opinion and is not proven fact. That is also true about this web site, it is my opinion and my opinion changes as I gather new information. The below discussion about moisture content and fermentation and crystallization is from the US agriculture dept so it can be believed as tested fact. The discussion about evidence of fermentation is my opinion.

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. If enough dextrose has left the solution the moisture content of the solution may become more favorable to the yeast if the honey was already close to or above 17% moisture, 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. If the honey is low in moisture, at 16.5% or less moisture, then even if it is crystallized it is unlikely that it can ferment as the remaining liquid will still be below 17.1% moisture.

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. Even this degree of warming does degrade the flavor some. It is best to harvest honey as dry as possible at about 16.5% moisture or below so that it can crystallize without any danger of fermenting.

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 experience temperatures of 115 degrees while still in the hive. I prefer to eat raw honey just as it is when it comes from the comb. Most of my honey is very high in dextrose from mustard flowers and will crystallize within two to three weeks after bottling. Since it is low moisture honey, 16.5% of less, it can keep for several years in this state with excellent flavor and no danger of fermentation as long as the jar is kept sealed between use. Many people prefer liquid honey over crystallized honey. Since my honey is so dry I must warmed it to 120 degrees F for several hours to liquefy it. This does degrade the flavor in my opinion, but some people prefer it. I will on occasion heat honey to 120 F to liquefy it. Any and all of my honey that has been warmed is clearly labeled with a label saying “This Honey has been warmed to 120 degrees F to re-liquify”. If there is no such label then it has not been warmed. I estimate that about 5% of my honey gets warmed before being sold. I consider the warmed honey to be raw, as I do not believe the temperature is high enough to degrade the enzymes that some desire in raw honey. I do think it does degrade some of the flavor esters adversely affecting the flavor, particularly if it is repeatedly warmed. If you agree 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%. According to US agriculture handbook number 335 Beekeeping In The United States 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 in the mid 16s about 16.5% so it is generally safe from fermentation.

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. I now dry my honey before extracting by placing the combs in a small room with a dehumidifier and fan circulating the air heated to about 85 degrees. After several days the honey is typically around 16.5% moisture so I am not concerned about fermentation of my 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 no longer recommend storing my honey in the freezer for long storage as I have stored it for 2 years at room temperature and it tastes excellent but it will definitely increase its shelf life you you are keeping it for many years.

If you have a moist honey 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.

I use to recommend keeping my honey liquid to prevent fermentation. That was because my honey tended to be moist in the mid 17 % range. Now that I can dry my honey before extracting I no longer recommend re-liquefying it. The honey tastes much better if it is never heated and is left crystallized. My honey is now typically in the mid 16% range of moisture. It is a lot of dextrose in it from mustard flowers in my area so usually crystallizes within 1 to 2 weeks of being bottled. Almost all of my honey shall be crystallized when you receive it.

Know the signs of fermentation:

As yeast grows it produces carbon dioxide gas. The carbon dioxide gas forms bubbles that will increase the pressure inside the jar. A bulging cap is an indication of pressure and is a sign of possible fermentation. In liquid honey the bubbles of carbon dioxide effectively increase the volume taken up by the honey and it may overflow the container pushing off the lid. Crystallized honey will often get very spongy from all the carbon dioxide bubbles, but again the pressure inside the jar will increase if the lid is air tight.

If you suspect that the honey might be fermenting but are not sure, taste it. If it tastes good and you like it don’t worry about it. Fermented honey is not bad for you like other canned foods that spoil from bacteria growing. The fermentation is caused by yeast growing not bacteria and it will likely be very minor unless the honey is very moist. Most bacteria is actually killed in honey by the high sugar content pulling the water from its body. If the honey tastes good use it. If you are really worried about it then store it in the refrigerator so the yeast does not grow, or heat it to 160 degrees in a hot water bath to pasteurize it killing the yeast.

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.

I use to believe that light feathery patterns seen in crystallized honey was a sign of fermentation caused by bubbles of carbon dioxide pushing the remaining liquid away from the crystals of dextrose. I use to counsel people to re-liquefy such honey to decrease the effective moisture content of the liquid. I was wrong. The feathery patterns are not a sign of fermentation. My honey is now quite dry and I see this feathery pattern in almost all of my honey that crystallizes quickly with fine crystals. It does not affect the flavor or storage life, tasting the same 2 years after bottling. I even see it in honey with less than 16% moisture which has no risk of fermenting even when crystallized. I do not know what causes it. I wish someone could tell me why it occurs.

Some of my speculation is that it is caused by the crystallized honey taking less volume in the organized structure of the sugar crystals as opposed to when the sugar is dissolved in the available water. It has never affected the flavor of the honey and I have looked for yeast with a micro scope without finding any. Also I have never experienced an increase of pressure in the jars which would have occurred if it was carbon dioxide bubbles produced by fermentation. Below is a picture of what I am talking about which I now believe is harmless.

Feathery patterns, I don't know what causes them but the honey is still good.

Feathery patterns, I don’t know what causes them but the honey is still good.

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.