After 3 weeks into Malo (MLF), I decided to check in on my wine in order to see how the conversion of malic to lactic acid was progressing. Question: How exactly do winemakers do this? Answer: Paper Chromatography.
As the process applies to winemaking and testing for MLF, paper chromatography is pretty strait forward. I have copied this text from the literature provided by the super cool guys at Oak Barrel/WineCraft:
“A special solvent migrates through a sample(s) of wine, picks up tartaric (heaviest), malic and lactic acid (lightest), and carries the lighter acids along its path at a faster rate than the heavier acids. When the solvent saturated paper is developed, the different acids are separated along a linear path. It is easy to see qualitatively whether malic or lactic acid is present, and the relative sizes of the two spots give a pretty good indication of the progress of MLF.”
Above is a shot of my chromatography worksheet. On a piece of paper turned sideways, I have drawn a line (approximately 1.25 inch from the bottom) and placed a series of X’s (approximately 1 inch apart) where I will later be applying my test samples and acids.
On the chromatography paper I have placed five distinct X’s. Just above each X will serve as the contact point for the 5 samples (in the glasses above) I have prepared.
The five samples include:
My 2 reference acids
1. 1 gram tartaric acid dissolved in 250ml distilled water
2. 1 gram malic acid dissolved in 250ml distilled water
The next 3 wine samples are from each of the 3 carboys that are currently going through MLF.
3. 50-75 ml of wine sample from carboy # 3
4. 50-75 ml of wine sample from carboy # 5
5. 50-75 ml of wine sample from carboy # 5-A
Here, I have taken a second piece of paper and folded it accordion style and labeled each trough with each of my carboy samples as well as my reference acids. I have used tiny capillary tubes to pull samples (each tube is filled about 2/3 full) of each sample. The trough makes it easier for me to pick up and handle each sample, which I let hang off the end of the paper.
Now I begin applying, one drop at a time, each of the 5 samples just above their respective X’s. Pressing the capillary tube (ever so gently) will release a drop of fluid. As soon as the fluid flows onto the paper pick up the tube. Allow the spot to dry (a few minutes) and go on to the next sample.
Ultimately, you’ll want to use up just about all of the fluid pulled for each sample. The key is to make sure that a) the paper dries between each application b) none of the dots overlap one another. Ideally, each dot should be around 1cm in diameter.
Next I stapled the edges of the paper to form a cylinder, making sure that the edges of the paper do not overlap.
Into my test jar I poured 50ml of chromatography solvent. I then inserted my chromatography paper into the jar with the data/dots side towards the bottom of the jar.
This process is known as ascending chromatography. I then sealed the jar, watched and waited..
And waited..after about 30 minutes, the solvent had begun to absorb the paper and creep upwards.
And waited..after about 2 hours the solvent had traveled approximately 1/3 of the way towards the top of the paper.
When the fluid finally made its way to within 1.5 inches of the top of the paper it was nighttime and 8.5 hours later. I took the paper out of the jar, removed the staples and hung the paper up in a well ventilated spot.
And like a bad tie-dyed T-shirt, in the morning, the dried paper yielded the results of my test! As I suspected, my wine has not completed MLF and is probably only around halfway complete. How did I determine this?
The second X on the paper (L-R) represents the malic acid sample. Halfway up the paper is a big yellow malic dot, indicating where the solvent ultimately carried the malic acid. My paper chromatography test indicates that samples #3, #5, #5-A still contain evidence of malic acic. Why? Because each of these samples also exhibits a yellow, albeit half the size, dot halfway up the paper and parallel to the big yellow malic dot.
What am I looking for? Basically, I want the yellow sample dots on #3, #5 and #5-A that are parallel to the yellow malic dot to diminish and ultimately fade away. When this occurs, it will indicate that the solvent has carried the lightest acid (which is lactic acid) to the very top of the paper. My yellow dots for the three wine samples will therefore no longer be displayed next to the malic dot, but instead above it and at the top of the chromatography paper.
Whew! O.K. enough analytical chemistry for now. I will conduct this test again, probably in a 3-4 weeks to see how MLF is going. Now it’s time to eat, drink and actually taste some finished wine..
Next: A tasting with Chateau Pradeaux!