There are a lot of discussions about the best way of making kava, from the starting material to the water temperature and the various possible additives to improve the yield or the taste of the kava drink.
Even if cooking is an art, it is also a physical and chemical process. This is also true for kava preparation. In the following, some basic principles in chemistry and physics used or appearing during the preparation of kava are discussed.
Suspension versus solution
The chemically active molecules in Kava are the so called kavalactones. Kavalactones like other natural molecules, e.g., cannabinoids, are poorly soluble in water (hydrophobic) but highly soluble in fat (lipophilic). On the opposite caffeine from coffee or the K@’s alkaloids are soluble in water (hydrophilic).
However, the similarity in solubility between the kavalactones and cannabinoids does not mean at all that the same physics is behind cannabis edibles and kava drink.
In cannabis, the CBD, or any other molecule of interest, is extracted by solubilization in a lipophilic medium like fat or alcohol. It means that the molecule as such is extracted from the plant and is solubilized in fat or alcohol.
A similar kind of extraction is also possible with the kavalactones of kava, but it is not what is done in the kava drink even if fat or water insoluble molecules are added in the water for the preparation of kava.
Indeed, the purpose is noted to solubilize the kavalactones but to obtain a so-called suspension.
A suspension is a material that is “swimming” in another medium and distributed more or less evenly in form of small particles. Fog is made of water droplets swimming in the air. Milk is made of fat particles swimming in water. The kava drink is made of small kava root particles in water.
Hence, the kavalactones remain in the kava root particles and are not solubilized in water.
And this is why kava size matters.
First of all, the smaller and the lighter the particle, the slower the sedimentation: the effect of gravity, directly linked to the mass of the particles, draws the particle toward the bottom of the bottle.
If the particle is sufficiently small, below the micrometer, the particle is subject to the so-called Brownian motion: the particle is moving randomly in any direction. However, even micronized kava is too big in size to “fly” randomly in the surrounding medium.
Secondly, the smaller the particle, the higher the surface/volume ratio. This is important since all the forces that allow the dispersion of the particle in the medium are acting on the surface of the particle. Hence, you want the biggest surface for the smallest volume.
If you have a cubic box with an edge of 3 meters, the surface is 6 faces at 9 square meters for a volume of 27 cubic meters (about the volume of a large U-Haul truck), hence a surface/volume ratio of 54/27 = 2
If you have a smaller cubic box with an edge of 2 meters, the surface is 6 faces at 4 square meters for a volume of 8 cubic meters, hence a surface/volume ratio of 24/8 = 3.
So, decreasing the size increases the surface/volume ratio.
Hence, the first effect of the strainer is to select the particles in such a way that they are small enough for the surface of the particles to play a role.
Well, but what happens at the surface?
The kava root particles are made of plant material. This material is made of long particles, like a chain of sugar-like units linked to each other (called polysaccharides), that are torn together in fibers. Those fibers, without being soluble in water, like nevertheless water (but not enough to be fully soluble) and swell at the surface of the particle: when you let your kava soak a while in water a crown of polysaccharide acting as float balls build up.
The number of “float balls” is directly proportional to the available surface. When the surface is large compared to the volume, it increases the “floatability” of your particle.
In fact, the polysaccharide at the surface acts as soap molecules. A soap molecule has a part that likes water, the other not. The part that does not like water sticks on the surface of the dirt particle while the other is in contact with water. Thanks to the part that is like water, the dirt particle can float in water and be washed away.
When lecithin or milk is added when preparing your kava drink, it is not the kavalactones that are solubilized, but the lecithin or some sugars or proteins in the milk that act as soap molecules, adsorb on the surface of the kava particle, and increase the “floatability”.
This has huge consequences for the bioavailability of the kavalactones in the body. Indeed, the kavalactones are absorbed by the digestive tract much more in the same way nicotine is absorbed from smoke by the lungs. It is of course harmless in the case of kava, since no carcinogenic molecules are built by burning.
Tobacco smoke is made of tar and ashes particles containing nicotine (i.e., a solid suspension of particles in a gas), those particles go in the lungs and nicotine is absorbed by contact of those particles on tiny blood vessels. Only part of the nicotine is absorbed. The smaller the particles, the higher the surface of exchange between the particle and the blood vessel: it explains why “light” cigarettes are strongly addictive, the filter provides smaller particles with an increased surface compared to the volume, increasing at the same time the bioavailability. In other words, there is apparently less nicotine, but from the nicotine present, more is absorbed.
The same is expected for kava in the digestive tract, the smaller molecules deliver the most kavalactones.
And here comes a question to which I have no answer:
the ratio of kavalactone absorbed in the digestive tract and the ratio remaining in the particle is not only a function of the surface of the particle, but also of the specific affinity of a given kavalactone for the particle against the affinity of the kavalactone for the digestive tract.
This ratio should be different for each kavalactone. Hence, when the analysis of a kava root gives, let say, 30% of the chemotype 2 and 50% of the chemotype 4, this does not mean at all that indeed in the body the ratio of the kavalactones in blood will be 30:50. If the chemotype 2 is “at ease” in the digestive tract and completely absorbed in the body while the chemotype 4 is more “at ease” in the particle and only half of it is absorbed in the gut, the effective ratio in the blood is 30:25. It may therefore well be that a kava with a chemotype starting with 24 acts in the body like a 42.
Has this question been studied?
