Recently, I wrote about the variations in pH readings I got with my meter. It appears I am also finding some variation in my enzymatic malic acid test results.
There are a number of tests and assays a winemaker should run to shepherd their wine to a clean and sound completion. Monitoring malic acid levels is one such key task.
Reds need malolactic fermentation to gain greater stability and a softer mouthfeel. Some whites (and pinks) need MLF, others absolutely do not.
It goes without saying, then, that malic acid levels need to be checked at a number of points along the production of various different wines.
To do this, I use the Accuvin Malic Acid Test. These kits come in different sizes and have an expiration date, so it’s best to buy the smallest kit needed. The test is a self-contained enzymatic assay on a strip.
It’s not a dirt-cheap test, but still quite affordable and very easy to run – unlike paper chromatography, which can take more than a day to run requires a larger set up as well as some nasty solvents.
Still, it has some limitations.
The Accuvin test is a useful, but not perfect tool. As the image above illustrates, the test may not give a clear indication of malic acid levels. For example, the November 11 Montepulciano assay and the Aglianico assays from both dates are a bit hard to read. So, I think it’s best to run a test a second time when the results are not immediately clear.
There is still some guesswork, or “eyeballing” (pun intended) when interpreting the results. The results fall on a scale of saturation of one color – unlike pH strips that change color with results. The reference chart can get a bit worn confounding interpretation a bit more.
Ultimately, one really wants to know if the malic acid is gone or not.
If the conversion seems to be dragging for whatever reason, the best option is to check again in a month or two. Inevitably, red wines will complete the conversion but re-inoculation may get things moving faster.