Wednesday, January 12, 2022

Update on Our 2020 Cabernet Sauvignon Wine

Just a little recap of our 2020 Cabernet Sauvignon and where it is now. We harvested our Cabernet Sauvignon and Cabernet Franc on October 22, 2020 and the grapes were destemmed and put into a half ton bin to settle until inoculation with the yeast F83 occurred on October 25. Fermentation was over around November 4 and on November 20, the must was pressed and the wine was put into a 75 gallon stainless steel keg. We inoculated the wine with VP41 in order to allow for the malolactic fermentation (MLF) to occur. My husband took a small sample of this wine so that he could run a paper chromatography test and then compared the results on February 17, 2021 which showed that the MLF had indeed occurred and that the malic acid had been converted to lactic acid. On February 26, the wine was racked into an oak barrel and the excess wine was put into 5-gallon stainless steel tank. The excess wine in the stainless steel tank was used to top off the wine in the barrel.
We periodically tasted the wine and could taste the influence of the oak on the wine. We thought that the oak was adding some complexity to the wine and this was a good thing. We also sent the wine off to Lodi so that we could know what the alcohol content of the wine was and the test showed that we had 11.46% alcohol in our Cabernet Sauvignon. We topped off the Cabernet Sauvignon in the barrel on August 23 and December 13, 2021 using the excess wine in the stainless steel keg.
When we went to top off the barrel on December 13, I thought that I smelled a hint of prunes on the wine and Jonathan Edwards concurred. The aroma was not that of dried prunes, but rather of fresh prunes and there was no flavor of prunes when we tasted the wine.
I didn't think much of it until, (in my cleaning) I came across a January 2020 issue of the Wine Business Monthly that we subscribe to. In that issue, there was an article titled, "Impact of Oxygen on Red Wines Aged in Barrels". What the authors did in their research was to follow the wine aroma modification and oxidation by monitoring the content of MND (3-methyl-2, 4-nonanedione).
The flavor of MND is reminiscent of prune, is very specific to “oxidized” flavors. The content of this compound increases with the oxidation state of the wine, which makes it a very good marker of oxygen supply and oxygen sensitivity of the wine.
The authors found that there are so called resistant wines, where Cabernet Sauvignon first pressed wines treated either oxidatively or reductively behaved in the same manner but the same Cabernet Sauvignon so called "second wine" showed higher levels of MND whether it was treated oxidatively or reductively.

While the article provided an answer to the aroma of prunes attributable to the compound MND (3-methyl-2, 4-nonanedione), it really didn't clear up for me how the impact of oxygen on a wine can lead to the evolution of unwanted aromas and flavors such as acetaldehyde and sherry notes as well as creation of the hospitable environment to lactic acid bacteria which can lead to production of ethyl acetate, acetic acid and other vinegar notes.
Maybe if I keep on cleaning the house, I can find other articles to answer this question.
References:
1. Alexandre Pons, Andrei Prida, and Philippe Darriet, "Impact of Oxygen on Red Wines Aged in Barrels", Wine Business Monthly, January 2020, ppg.
2. Image from TCI.

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