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!

Salud!

First Vintage

Last October I posted about my first winemaking experience; well at least from crush through the primary fermentation and press. That was probably the most involved part of winemaking, when twice to thrice-daily punchdowns took place with constant measuring of temperature and Brix. That was when the juice was transformed from 'must' to wine as sugar got fermented into alcohol and carbon dioxide.

Secondary Fermentation

After the press, we moved into secondary fermentation of the wine in air-locked vessels. We used a 5-gallon glass carboy and three gallon jugs to use for top-up (I'll get into that later). This period was generally uneventful and less involved, but there were a few things that required attention.

Controlling the temperature. Malolactic (ML) bacteria, which was added to the juice the day before press, were quietly converting tart-tasting malic acids into fuller-bodied lactic acids. ML bacteria are sensitive to numerous factors (e.g. pH, SO2, and alcohol levels), but the one thing that worried me was my ability to keep the wine within the optimal temperature range (>70 degrees). The carboy and gallon jugs were wrapped in blankets, snugged in cardboard boxes, and gently warmed by a heating pad. My biggest fear was stuck fermentation since there were no easy tests to perform at home or measurements to track progress. I resorted mostly to prayers.

Lees left behind from racking

Racking, racking, racking. Even though most of the solid remains of the grapes and yeast (also known as pomace or marc) were removed during the press, there were still some remaining in the wine as it went through secondary fermentation. These are called the lees. Decomposing yeast in wine could cause off flavors. In order to remove the lees, we did multiple racking of the wine during secondary fermentation. Racking is the process of siphoning wine off of dead yeast into new containers.

We siphoned a total of four times; the first time was 24 hours after press, the next two were a week apart, and the final one was a month out.

Racking also has two other advantages:

• It clarifies the wine. You could literally see that the juice got clearer after each racking. In many cases, clear wine is just a matter of aesthetic. If the wine tastes good, cloudiness may not indicate flaws.
• When done correctly, racking can introduce controlled amount of oxygen into the wine. During the early part of secondary fermentation, oxygen has positive effects on unfinished wine by stabilizing the color and tannins. It allows the wine to mature gracefully and become more complex. In the later part of the secondary fermentation, caution is needed to minimize oxygen contact. If acetic bacteria is exposed to wine and oxygen, it will turn the juice into vinegar (acetic acid). 

It is important to note that you will lose wine during racking due to spills and as you avoid siphoning lees. The loss of wine during racking may increase the air space between your wine and the airlocks. You can top up the carboy with wine from the jugs or similar store-bought wine (preferably same varietal and AVA). Alternatively, you can add sterilized marbles into your containers to raise the wine level. I personally put some of my top-up wine into a sanitized plastic container, squeezed out as much air as possible, and capped it. It worked!

Final Testing

After more than three months of secondary fermentation, we performed the final testing of our wine to check on sugar, acidity, and ML fermentation. During the primary fermentation, which lasted less than two weeks, I was constantly monitoring and measuring progress. For the much longer secondary fermentation, I really had no idea what to expect. But I was pleasantly surprised by the outcome.

• Residual sugar was at 0.3%. This was probably the least of my concern since we pressed the wine at a really low Brix. Residual sugar over 0.6% is a concern for still red wine as it may cause re-fermentation in the bottle.

Measuring residual sugar in the wine

• pH was 3.78. This was slightly higher (or less acidic) since harvest, which was at 3.53. But it was still within the normal range.
• Titratable acidity (TA) was 7.3125. TA measures the amount of total acids and was higher than our reading during harvest, which was 7.125. It was a bit higher than I like, but not bad.
• ML fermentation appeared to have completed. While not the most accurate way to test the concentration of malic acid, the chromatography test is cost-effective. The solvent used for the chromatography is extremely toxic, and the test takes several hours. After putting dots of wine sample onto a piece of chromatography paper, it was left in a big glass jar with the solvent and the lid closed tight. 

With one exception, most of the wines appeared to have completed ML fermentation. Yellow patches indicated presence of acids. The top row of yellow revealed the presence of lactic acid, which is the goal of the ML fermentation. The bottom row of yellow revealed the presence of tartaric acid, which is also what we expected. Any yellow in the middle role revealed the presence of malic acid, which would indicate that ML fermentation has not completed. This would show that the wine has not stabilized and will need more time for ML fermentation to complete.

Chromatography test revealed that one of the wines still had malic acid

Bottling

Once the wines had passed all the tests, they were ready to be bottled. We got the bottles that we have saved up, cleaned, and sanitized. (We recycled bottles. If you buy new bottles, you can skip the above steps.) Sulfites were added to the wine just before bottling. Sulfites are a preservative and will keep the wine fresh. They are also anti-oxidants and will protect the wine from oxidation.

Adding sulfites to wine

Siphoning wine into bottles

Corking wine bottles

Finally, five months after harvest and crush, our first vintage was bottled and proudly named Abscession - a joke, as my husband was recovering from an abscess the day of the harvest. Special kudos go to my partner-in-wine, Alisa. That's her work on the label, making an access look classy. The wine will officially be released in the summer, so check back later.

Abscession 2016 Syrah

My Verdict: I am having so much fun learning about winemaking. It gave me a greater appreciation for wine. I don't think going commercial is my calling, but I'm planning for my next vintage already!