30 ppm or 300 ppm, that IS the question

Just found this old draft of a post…might as well post it! I did get an aswer from the lab..I’ll post that later.


The ’11 syrah barrel has been silent for some time now, indicating probable MLF completion.

I checked it with an Accuvin Malic test strip. They are really convenient, so I would really like to be able to use them. The strip showed no color, also indicating MLF completion.

I took a sample to Vinquiry, and had a malic acid test performed. The test results indicated 10 mg/100 mL, or 100 ppm, indicating NOT complete. The industry standard is a max of 30 ppm for completion.

This is exactly what happened to us last year. Vinquiry results never indicated complete, but both Accuvin and BevPeople Reflectoquant tests indicated complete. Last year we dropped the investigation, called it complete, and drank the wine! The winemaker in me says WTF! why am I wasting time on these trivialities? The engineer in me says something is fishy; gotta figure it out. Last year the winemaker wins, this year the engineer!

First I did a bunch of research, and checked with BevPeople to make sure the 30 ppm number is correct. I then put together the following email summary of the situation, and fired it off to Vinquiry:

I have an issue with the results of your malic acid tests. What follows is the sequence of events that is causing my confusion, and I am looking for help in clearing up my confusion! It has cost my colleague and I a lot of time and money, and I do not want to use Vinquiry again for malic acid tests until I understand what Vinquiry is doing.
Here goes, starting in the beginning of 2011:
  • Jan 19, 2011:
    • 30 gallon ’10 Syrah:
      • Vinquiry test: 9 mg/100mL = 90 mg/L = 90 ppm
      • Accuvin test strip showed no color, indicating MLF complete.
    • 13 gallon Syrah:
      • Vinquiry test: 24 mg/100mL = 240 mg/L = 240 ppm
      • Accuvin test strip showed some color, indicating not quite finished.
    • My understanding is that the threshold for being bottle stable is 30 ppm. Many sources state this number. I have attached one source from Cornell University, called MalolacticAcid3Ways.pdf. Based on the Vinquiry test results, and the belief that the Accuvin results are difficult to judge, I assumed that out MLF was not complete.
  • Feb 14, 2011:
    • 13 gallon ’10 syrah:
      • Vinquiry test: 7 mg/100 mL = 70 mg/L = 70 ppm
      • Again, based on the 30 ppm threshold, I decided MLF was not finished.
  • Mar 11, 2011:
    • 13 gallon ’10 syrah:
      • Vinquiry test: 11 mg/100 mL = 110 mg/L = 110 ppm
      • Again, not finished, but actually worse. At this point we decided that maybe we were not stirring it properly, or sampling properly. So we very carefully stirred the lees twice a week, and kept the temperature at 65F with a heater and thermostat.
  • Apr 6. 2011:
    • 13 gallon ’10 syrah:
      • Vinquiry test: 12 mg/100 mL = 120 mg/L = 120 ppm
      • We are now very frustrated, having spent a LOT of money on tests.
      • We took samples of our three barrels to Beverage People and measured malic acid with their reflectoquant system.
      • BevPeople reflectoquant test = 20.3 mg/L = 20.3 ppm, indicating MLF complete.
    • 30 gallon ’10 syrah:
      • BevPeople reflectoquant test = 14.2 mg/L = 14.2 ppm, indicating MLF complete
    • 15 gallon ’10 surah:
      • BevPeople reflectoquant test = 16.4 mg/L = 16.4 ppm, indicating MLF complete.

At this point we were very upset, didn’t know what to think, but because Accuvin and Reflectoquant tests indicated MLF complete, we decided to ignore the Vinquiry results, and call it complete! I should have called Vinquiry and worked this out, but I just didn’t want to deal with it.

We are happily drinking the ’10 at this point!
On to 2012:
  • This year I attempted to monitor the progress of the MLF by listening to the crackle of the bubbles in the barrel. I knew we were sugar dry based on a post fermentation Vinquiry panel, so there was no sugar ferment going on.
  • Nov 19, 2011: Inoculated for MLF with Enoferm Alpha. No crackle sounds from the barrel.
  • I stirred twice a week, and held the cellar temp at 65 F. I could clearly clear the crackle of the MLF by Dec 5.
  • Jan 9: Slight crackle coming from barrel.
  • Jan 22: No sound coming from barrel.
    • Accuvin test showed no color indicating MLF finished.
  • Jan 23: Vinquiry test: 10 mg/100 mL = 100 mg/L = 100 ppm, indicating NOT complete.
  • Here we go again! At this point I called Vinquiry. I spoke with someone who told me that the Vinquiry threshold for MLF being complete was 30 mg/100mL = 300 mg/L = 300 ppm, so our test indicated complete by this threshold. But this is a factor of 10 larger that what seems to be generally accepted in the industry.
  • I downloaded the Vinquiry procedure off of the Vinquiry website. It clearly states the 30 mg/100 mL threshold, a factor of 10 off of the industry standard.
I did some research on the web and found this link describing the enzymatic procedure:
The equation in there is very similar, but does not have the extra 10 in the denominator. If I plug in the volumes from your procedure into their equation, I get a result of:
c = deltaA * 2.6775  g/L = deltaA * 267.75 mg/L
This result is off by a factor of 10 from your equation in your procedure.
Bottom line: I think that although your tests claim to report in units of mg/100 mL, I think you are really reporting in units of mg/L. If this were true, then the results I was getting indicate that the MLF is finished, and that your result showing 10 is actually 10 mg/L = 10 ppm, which meets the accepted threshold of 30 ppm.
I would really like to understand the discrepancy. I consider tests that I have done via Vinquiry to be closest to the “truth”, but if the numbers don’t match up with the literature, then something is wrong.
Any thoughts? The reality is that I don’t understand the details behind the procedures, and my analysis could easily be wrong, but still, the standard for Bottle Stable from Vinquiry is 10x larger than the standard usually quoted (see attached paper from Cornell). How can that be?
I have attached the above quoted test results from Vinquiry.
Niels Jensen
Poppyseed Cellars

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