Acetone testing is the easiest and most common method for testing kava quality, but is it really effective?
Acetone tests work like this: a portion of kava powder is mixed with an organic solvent, e.g. acetone, in a small test tube and shaken. The mixture is allowed to settle overnight and the supernatant liquid above the root material is analyzed for color. The idea is that if the kava is tainted with tudei or wichmanii strains of kava, then the supernatant will take on a reddish appearance, whereas purely noble kavas are pale yellow.
There have been recent reports that noble kava strains can give false positives, because the roots may have certain reddish compounds in the bark. This is something we have confirmed in our laboratory at Fiji Fresh. In addition, we also have found that the method of preparing kava can strongly impact the coloration of an acetone tests. Let me explain.
In the first figure below, I show 4 samples. From left to right are: (sample 1) a commercial, tested and verified noble kava; (sample 2) our House Waka, freshly pounded; (sample 3) our House Waka ground in a coffee grinder; (sample 4) and our House Lewena ground in a coffee grinder.
To be clear, the right three samples are from the same plant, just from different parts or prepared in different ways. The third and fourth samples easily pass the acetone test, but what about the second one? I'm sure that most would say this is a tainted or tudei modified kava.
And yet, it cannot be tainted, because I pounded this root myself, from the whole root of a single plant. It's a single strain, and therefore it must be either noble or not noble. If it is not noble, e.g. piper wichmanii, it would be deep red in color. But it is not. It's a noble plant, grown in Savusavu, Vanua Levu, Fiji. And, moreover, there are no tudei plants or wichmanii strains that are cultivated in Fiji.
What could cause the color to be amber tinted? My hypothesis was that our traditional pounding methods combined with immediate packaging creates a kava with many more finer particles than usually found in medium grind kavas. These extremely fine particles have complex light scattering properties that are light wavelength-dependent.
The phenomenon responsible for color tinting in particle suspensions is called the Tyndall effect. Shorter wavelengths (blue light) scatters more than red, which causes an overall reddening of the liquid appearance (coincidentally it is analogous to the same phenomenon that causes sunsets to appear red, and even more so when there is more pollution in the air). This hypothesis was supported by the additional observation that it took more than a week for the particles to form a sediment at the bottom of the glass vial. With so many small, slow moving particles, it seemed very likely that there were still suspended particles remaining suspended that simply haven't (or won't) sediment.
To test the hypothesis, I purchased a simple centrifuge from Amazon. If there were suspended particles, I should be able to change the color of the liquid by pulling particles out with the centrifuge. On the other hand, if the color did not change, then I would know the color was caused by molecular compounds in the plant that are dissolved into the acetone (an indicator the plant is not noble).
Results. Each sample was centrifuged at ~3000 rpm for 20 minutes and re-examined. The results confirmed the hypothesis. Although one of the samples (the coffee ground lewena) was damaged during the test, I was able to alter the color of the pounded waka using the centrifuge. The samples post-centrifuge are shown below. From left to right in the same order as above: (sample 1) the commercial, tested and verified noble kava; (sample 2) our House Waka, freshly pounded; (sample 3) our House Waka ground in a coffee grinder; (sample 4, rip) a placeholder for the damaged Lewena sample.
The difference in color of the second sample (from the left) is significant. It is also straightforward to conclude that the this is a noble kava strain. Here is a side by side comparison:
In summary, acetone testing is probably good for most circumstances, but I am not confident that it is a flawless indicator of kava quality. This is why we test our kava using a full spectrum of tests, including HPLC and microscopy analysis.