One thing that puzzles a lot of new (and used) beekeepers is the way that some honey granulates while other honey doesn’t. There are a number of things that affect crystallization rate, including ‘seed’ floating in the honey (dust, previous granulation bits, bees’ knees), temperature (granulation happens more quickly at about 10C/50F), moisture (drier honey solidifies faster), and floral type. Floral type may be the most important, so let’s look at that.
As you all know, nectar collected from different flowers has different chemistry – aromas, flavours, minerals, acids, water content, sugar types. If we focus on granulation, the important element is sugar type. When plants create sugar, the sugar begins as sucrose – like common table sugar. Sucrose is a disacchride which enzymes can break into two monosacchrides – glucose and fructose. Bees add most of the enzymes, though some of the activity begins back at the flower. Glucose and fructose, the products of enzymes acting on sucrose, are both sugars, but they are quite different.
Fructose is about twice as sweet as glucose. Honey high in fructose (tupelo, black locust, sage) is much sweeter than honey lower in fructose (honey dew, dandelion, buckwheat). When I say ‘high’ in fructose, I mean honey with about 40% fructose while lower fructose honey is around 30%. The rest of the honey is made of water, glucose, some sucrose, and other sugars. Here’s a chart I made of average compositions of 490 samples of USA honey:
You can see that honey varies a lot. These numbers come from 490 samples, collected and chemically analyzed by the USDA. They represent about a hundred different floral types or blends of floral types. Looking at glucose content of honey, we see it can be as low as 22% in some samples and as high as 41% in others.
The amount of glucose is the most important factor in determining whether honey will granulate. Varieties such as dandelion, canola, and cotton are over 35% glucose. These honeys don’t last long in the liquid state.
You may be wondering why different honeys have different amounts of glucose (or fructose or other components). In a future post, I’ll give an explanation, but for now, keep in mind that the same variety (say, canola) will have approximately the same fructose/glucose ratio whether it’s produced in Poland or Canada or on sandy soil or deep loam. I think that’s pretty cool – plant biology determines sugar ratios.
When it comes to granulation, the most important factor is the floral type and its percentage of glucose. You usually can’t do much about that, unless you purposely move hives to avoid some flowers. One of the things that you have a little control over is moisture. Although it’s always a good idea to harvest fully-ripened honey with less than 18.6% moisture, drier honey will crystallize more quickly. If you think of honey as a supersaturated solution with glucose suspended in water, then if you have less water, you have a more saturated solution. Highly saturated solutions precipitate solids. In honey, that’s called granulation. So, dry honey crystallizes more quickly.
Here’s a graph I made that shows how moisture and glucose are related:
Here’s how this chart works: everything above the blue line granulates within six months. Let’s say that your honey is from tulip poplar, which is usually about 26.5% glucose (see the table, right). You can expect your tulip poplar honey to crystallize if the moisture content is below about 16.5%. If the honey is wetter than that, it will probably not granulate very quickly or at all. Of course this depends on your honey being purely from tulip poplar trees and not mixed with spring fruit bloom or basswood.
On the other hand, if your honey is from one of the sources which typically have more than 30% glucose, you can see from the graph that no amount of moisture level will keep it from granulating. Well, that’s not strictly true – if water content is, say, 25%, it may stay as a liquid for a long time. But it will ferment, sour, bubble out, and taste awful. In fact, the law says honey must be below 18.6% water to be legally sold as ‘honey’. Anything higher can be trouble.
One last thought. If you work with honey, you’ve probably encountered containers that are watery near the top, but granulated just below the syrupy surface. Honey can absorb moisture from the atmosphere in a humid climate. (To some extent, the water in honey may also float up above the solids.) When you see honey like this, it’s because the upper part of the jar has high moisture. Because of the higher water content, the top hasn’t granulated, but instead may smell sour.
Digging down into the jar a bit, you likely find chunky crystals of honey. This is likely the exact same honey type, but the difference in granulation is due to the water content of the honey – wetter on top, drier below. The photo, above, illustrates this rather nicely. As long as the surface honey hasn’t begun to sour or smell yeasty, you can pour off some it, melt everything, and stir it. This restores the honey to something more palatable – as long as the resulting newly stirred and melted honey isn’t above 18.6% moisture.
If you are interested in honey qualities in general, you might like this presentation I made about a year ago for the local bee club. It goes into a lot of detail on honey chemistry: