Monday, February 11, 2008

Summary Of The 07 Rancho Sarco Cab Ferment

Today I racked the 2007 Rancho Sarco Cabernet out of the WinePod and into the 20L Vernou barrel and a 7-gallon carboy, marking the completion of the active winemaking phase of this lot.

When I drained the barrel this morning the water was again medium-brown. The smell of the wood in the barrel was markedly less than after the first soak. It is my hope that after making four hot water extractions of this wood, the amount of "oak" the barrel will impart to the wine will be moderated to some degree.

I used the 7-gallon carboy to receive the balance of the wine in the Pod, expecting that the volume might be a little greater than 5 gallons (my other carboy option). After I confirm that the malolactic ferment is complete I will add SO2 (as Efferbaktol) to the barrel and the carboy, settle the wine in the carboy and rack it to fill a 5-gallon vessel. Any remainder I will put into screw-cap bottles with extra SO2 to use as topping wine.

I ran a sample to the lab for a quick check on malic level and pH:

Malic Acid0.18g/L

The earlier carbonate addition raised the pH to nearly exactly where I had hoped – recall that pH 3.6 was my target. The malic level is below my personal "done" threshold of 0.20 g/L but I think I will wait a bit longer before I add SO2 to the wine.

Fermentation Summary

I essayed this ferment to test the current pre-production version of the WinePod, and to prove the quality of the Rancho Sarco Cabernet fruit. I feel I had a postive result on each count: the current version of the Pod is very much "ready for prime time" in my opinion, and the Rancho Sarco Cabernet can be made into a really outstanding wine in the Pod.

For the most part, how I conducted this ferment could be duplicated by anyone who owns a Pod. The few exceptions I included (using enzyme, some tannins not currently included in the consumable kit, and liquid yeast extract) should have made – at most – a minor difference to the outcome.

I was able to demonstrate how to use the Pod controls to mimic the temperature profile of a commercial ferment, and also to emulate the operation of a commercial vertical basket press. I would expect these functions to be automated options in future iterations of the WinePod firmware and software.

As I mentioned in an earlier post, should I ferment another lot of the 2007 Rancho Sarco Cab I would add 0.2 g/L of tartaric acid before the ferment rather than the 0.5 g/L that I added this go-around. In the future I may experiment with larger additions of tartaric and then of potassium carbonate, in sequence, to increase the buffer capacity of the juice expressed from previously-frozen fruit.

In a future ferment of this fruit I would also bump the total addition of nitrogen (as DAP) to at least 75 g/hL, and perhaps as much as the maximum allowable addition of 100 g/hL. These values represent actual DAP additions of 30-32 grams and 40-43 grams, respectively.

The resulting wine is something I would be proud to bottle commercially. The color is deep and of the proper hue. The aromas are rich and correct for the varietal and the location of the vineyard. The texture on the palate has wonderful grip and balance, and the finish and aftertaste are long and pleasant. The result here is perhaps better than I have ever achieved before in a small-scale red wine fermentation trial.

I would hope that someone with no prior winemaking experience could follow the protocol I have outlined here and obtain a similar result. That said I refuse to accept any personal liability for someone else's failure to make a wine of the same quality. As I have told my professional consulting clients over the years, there are tens of thousands of wrong ways to make wine, but maybe many hundreds of right ways.

I honestly don't know how much of what I achieved was a consequence of my own level of experience keeping me from making mistakes, or keeping the consequences of my mistakes to a minimum. But I am sure I have not even scratched the surface of possible failure modes.

But the bottom line is - with the WinePod and good grapes I believe that anyone COULD be a rockstar.


Greg said...

Hi John,
Very cool!

How much carbonate did you add and how did you calculate the buffer capacity requirement?

If you made it again, would you add it with the acid, pre-fermentation?

John M. Kelly said...

Hi Greg: I didn't do anything as sophisticated as a buffer capacity calculation in determining the carbonate addition. Rather, this was a "seat-of-the-pants" approximation.

Here's how my thinking went: The initial juice pH was 3.78 with a T.A. of 4.21 g/L (lab numbers). Before the ferment I made a rough pH measurement in the winery that I didn't fully trust, and had my own taste which I trusted more – both suggested that the juice needed some acid. So I made a tartaric addition of 0.5 g/L.

My rule of thumb is that a 1 g/L addition of tartaric changes the juice pH by 0.1 units – my addition was conservative. But when I got the post-ferment lab numbers back the pH was 3.46 – the acid addition had moved the pH by 0.32 units.

I have some prior experience with frozen fruit that led me to expect that this might happen. Freezing precipitates potassium bitartrate from the juice and decreases its buffer strength.

A final pH of 3.46 was not my goal for this ferment. The en vogue style of Cabernet that gets the high scores these days usually has a pH of 3.7 or higher. So I chose to add some potassium carbonate to move the pH up a little.

As with the tartaric addition, my rate of carbonate addition was conservative. Another rule of thumb is that one gram of carbonate will remove 2 grams of tartaric and move the pH up by 0.2 units. I added 0.1 g/L (expected pH change, 0.02 units) and moved the pH up by 0.12 units. Some of this pH increase was due to the conversion of malic to lactic acid in the wine, but the bottom line is I ended up with a wine near pH 3.6 (in the range I wanted) that has a great texture and balance on the palate.

Sure, I might think to duplicate this in another ferment of the 2007 Rancho Sarco fruit. If I did, I probably would not add them together. I would add 20 grams of tartaric on day one with the first mixing punchdown. Then I would add 4 grams of potassium carbonate at the second or third punch before the onset of fermentation.