My 2007 Barbera has been cold soaking since it was harvested and crushed this past Sunday. A cold soak for me means rotating gallon jugs of frozen water in the must (juice from crushed grapes, skins, pulp, and so on) on a daily basis. It’s important to keep the must cold so the juice doesn’t start fermenting on its own, or worse, the start of a bacteria problem.
The purpose of a cold soak is to give the juice more time with the skins and pulp to extract more color and flavor. Since my primary fermentations rarely take more than a week to complete due to the warm conditions in my garage, this “quality time” up front seems to be making a big difference. In just a few days the color of the Barbera juice has reached an absolutely beautiful inky dark ruby.
Another benefit of letting the juice, skins, and pulp soak like this before starting the primary fermentation is that the berries can become completely rehydrated. This is important since as the berries rehydrate, the sugar level, or Brix, in the juice will rise. By letting this happen before inoculating with yeast you have an opportunity to make adjustments as needed. Since some of the Barbera clusters were showing signs of raisining, I expected the Brix to climb. And boy did it climb!
Testing the Brix can be done with a hydrometer or, before the primary fermentation has started, a refractometer. A refractometer is a small hand held device that measures the refractive index of a sample (grape juice in this case) when viewed through a measuring prism. This indispensable tool is used in vineyards as a tool to determine ripeness in grape samples. As you can see below, my personal refractometer assistant was on the spot to lend a hand this afternoon.
Her reading today was a whopping 28.5° Brix! Why is this so important? Well, if all of the sugar was fermented at this level, we’d be talking about a wine in the 16% alcohol range! Not exactly what I’m looking for. And this doesn’t take into account any problems being able to even complete the fermentation (i.e. take the juice all the way to dryness, or zero Brix). This is called a stuck fermentation and is something all winemakers generally try to avoid.
A common solution to this condition is to add acidulated water to the must to dilute the sugar only and bring the must back into balance. Acidulated water is simply distilled water with tartaric acid added. Tartaric acid is added to the water so we only dilute the sugar and not the acid level in the juice.
So that’s what we did this evening. The must is back down to just over 25° Brix. My plan is to start the primary fermentation in the morning.
UPDATE: If the thought of adding water to must to dilute the sugar content is abhorrent to you, you’re not alone. The fact is, though, grape juice has been routinely “adjusted” prior to fermentation for centuries. For example, on the opposite side of the high sugar spectrum is not having enough sugar. This occurs when either the fruit was picked too early or the fruit could not ripen on its own. The solution to this problem, as you might expect, is to add sugar–also called chaptilization. Winemakers in many of France’s cooler wine regions have no choice but to add sugar to their under-ripe juice. In fact, the option of adding sugar is even written into France’s wine regulations.
So what’s the difference here between adding water or adding sugar to juice at harvest? Or is there no difference at all? Is it acceptable to add sugar since it was Mother Nature and not the wine grower that created the imbalance in the juice? After all, by picking late to extend the fruit’s “hang time”, the wine grower is purposefully pushing the envelope of ripeness to maximize the body, fruit characteristics, and color of the resulting wine.
Or perhaps the demonization of adding water is getting swept up in the growing backlash against over-extracted and high alcohol wines? More discussion on this issue here and here. Also, if you want to listen to a lively discussion between old world and new world style Pinot producers, check out Grape Radio’s Pinot Showdown series.
Coming back to my tiny lot of Barbera, my motivation for adding water was simply to avoid the problems that often come with trying to ferment juice with such a high sugar content. And if I manage to create wine with a moderate alcohol level while not losing the character of the fruit, I will consider it a success.
Another important daily task is to measure the Brix, or sugar content, and temperature of the wine. This is done by filling a tall narrow container with some of the wine and gently dropping in a hydrometer. Once the hydrometer is finished bobbing and comes to rest, a measurement can be read from its side. This morning’s reading was 15° Brix. Fermentation is moving along nicely but still has a ways to go before it’s done. 
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