Saturday, October 26, 2019

Tracking the 2019 Cabernet Franc Numbers

This is the first year that we will be having a good amount of Cabernet Franc to harvest. We have waited this long to harvest the grapes because of an abnormally high amount of titratable (TA) acid in our sampling.
Here is a recap of what we have been seeing:
Variety Test Date # of Berries Weight Volume
of Juice		 Brix pH TA
Cabernet Franc 9/14/2019 45 47 g 15 mL 16.5 2.68 NA
Cabernet Franc 9/30/2019 40 48 g 17 mL 20.4 2.98 9.1 g/L
Cabernet Franc 10/5/2019 40 58 g 15 mL 21.6 2.99 11.9 g/L
Cabernet Franc 10/13/2019 40 53 g 20 mL 21.4 3.09 13.3 g/L
CF Clone 214 10/20/2019 30 36 g 12.5 mL 23 3.13 11.5 g/L
CF Clone 327 10/20/2019 30 39 g 10 mL 22 3.04 11 g/L
Cabernet Franc 10/23/2019 76 86 g 35 mL 22.4 3.10 9.3 g/L
On October 20, we decided to take readings on our two clones of Cabernet Franc separately to see if they were any differences with the Brix and the titratable acids. Our readings show that they were within range of each other although clone 327 seemed to be a little behind. On October 23 when we took our last reading, we finally had a titratable acidity that we could live with.
The other experiment that my husband conducted was a paper chromatography experiment. Here, we wanted to qualitatively see what the ratio of tartaric acid to malic acid was.
Here are the results:
In paper chromatography, the compound with the lowest molecular weight will move the farthest. Therefore, in lanes 1 and 10, lactic acid is at the top of the chromatogram. Similarly in lanes 2 and 9, malic acid is in the middle of the chromatogram and in lanes 3 and 8, tartaric acid can been seen as being lower than the lactic and malic acids.
In lanes 4-7, my husband spotted the samples of interest to us. Since we know the titratable acids of our 2019 Barbera, 2018 Cabernet Franc wine, 2019 Cabernet Franc juice and 2019 Cabernet Sauvignon juice, we were interested in the qualitative comparisons as determined by the paper chromatography. The 2018 Cabernet Franc wine in lane 5 is the only lane that showed any appreciable amounts of lactic acid, indicating that the wine underwent malolactic fermentation and converted some of the malic acid to lactic acid. Comparison the Cabernet Franc juice in lane 6 to the Cabernet Sauvignon juice in lane 7, a case can be made that the Cabernet Sauvignon juice might have a bit more malic acid.
We are harvesting our Cabernet Franc today and holding off harvesting our Cabernet Sauvignon until a little later in the coming week.
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2 comments:

  1. UnknownOctober 28, 2019 at 7:55 AM

    Wondering why you think the 2018 Cab Franc has completed MLF? Do you typically have residual Malic at the end of your MLFs?

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  2. HanumangirlOctober 29, 2019 at 4:33 AM

    Hi! thank you for your comment. We took the reading of the 2018 Cabernet Franc that we had already bottled! We had no idea and wanted to see if this wine had undergone spontaneous malolactic fermentation (MLF) and were surprised to see that it had. Since this was the very first Cabernet Franc wine that we made, we had no idea what to expect. The titratable acidity for the wine was 9 g/L at the end of fermentation. For our 2019 Cabernet Franc, we currently have titratable acidity of 9.3 g/L and will do a MLF after the primary fermentation and will take another chromatogram for comparison. That will be more meaningful. Thanks for your comment.

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