Thursday, May 31, 2018

A Wine Geek's Experiment with Oak

Last summer, I wrote My Wine is Too Oaky, a post on oak and its influence on wine. Much of what I knew about the interaction of oak and wine was theoretical. Then I got to experiment with oak when making my 2017 vintage. I had purchased the wildly popular Red Mountain Cabernet Sauvignon from Artz Vineyards. Cabernet Sauvignon and other more tannic grape varietals make austere wine on their own so they benefit greatly from the softening effect of oak. But how does that really work?

Oak & Oxygen

Wine develops differently in an oak barrel versus a glass container. Oak barrels are porous and release a small amount of oxygen to the wine. The gradual release of oxygen, known as micro-oxygenation, takes the edge off of grape tannins, giving the wine a softening effect. Oak barrels also have their own tannins that further protect the wine from oxidation and reduction. Additionally, many winemakers favor oak for the phenols that impart flavors, such as vanilla, cocoa, and spice, to the wine. Glass carboys offer none of these benefits.

Wine in barrel and carboys
I got a 7.5-gallon tight-grained medium-toast new French oak barrel from Radoux Cooperage. There is a slight challenge with an unused small oak barrel. The newness and a larger oak surface area to volume of wine translates to a higher concentration of phenols in the wine. The amount of flavor imparted can easily overpower the juice, like an over-salted dish. Fortunately, a few friends had joined me in making that vintage so we had plenty of juice among us, about three times the volume of the barrel. The idea was that we would rotate the juice in and out of the barrel till we reached the taste profile we wanted.

Round Robin

After our crushed grapes and juice (known as must) had completed the alcoholic or primary fermentation, it became wine. The wine was pressed and then transferred into glass carboys for malolactic or secondary fermentation. During this process, the tart malic acid found in grapes was converted to softer-tasting lactic acid with the help of lactic acid bacteria.

In the early stage of malolactic fermentation, the wine was moved from one container to another at certain intervals to get rid of sediments. The process is known as racking. The discarded sediments, known as the lees, are primarily made up of dead yeasts and grape debris.

About three weeks into malolactic fermentation and during the third rack, we moved a third of our wine into the new barrel for the first time. The remaining two-third returned to glass carboys. We monitored the wines monthly; topping up, testing, and tasting. The wines remained in their respective receptacles for another two months before they all completed malolactic fermentation. We were pleased that all the wines did well even as different taste profiles gradually developed.

Racking wine from carboys into the barrel
When we were satisfied with the taste of the first batch of oaked wine, we racked it out of the barrel into the carboys. In its place, we pumped in a fresh batch of un-oaked wine. Thus, the round robin continued until all the wine had cycled through the barrel for one to two months.

Taste Test

The fun part of the experiment is the sample tasting! We tasted both oaked and unoaked samples over time. We took notes and observed the evolution of the wine, our ability constantly tested with a bit of voluntary intoxication.

After over five months of tasting during the round robin, the taste profiles of the different samples confirmed our theory:
  • The sample with little to no oak was bright with high acidity. The tannins remained coarse, and the wine ranged between low to medium-bodied.
  • The sample with at least two months of oak contact had more concentrated cherry, vanilla, cocoa flavors with medium acidity. The tannins were distinctly smooth and velvety, and the body was medium to full.

Tasting wine samples
My Verdict: By the time we were ready to bottle, all the wine had cycled through the barrel. We did a final taste test to ensure that there were no surprises. Thankfully, there were none. We blended the wine together and were delighted with the end result. At the time of this blog post, the wine has been aging for a month in the bottle. For a first vintage with oak, I pronounce it an overwhelming success. I look forward to tasting it after another five months of bottle aging. Stay tuned!