Cold Soaking in Wine Making

On the back label of many Pinot Noirs we see the term “Cold Soak” listed as part of the winemaking process. If you make your way into a tasting room in the Sonoma Valley of California or the Willamette Valley of Oregon, you may have a winemaker or tasting room host divulge in a very quick succession of words that the wine in your glass was cold soaked for 3 days, for example. In California, we almost expect to see most mid- to high-end Pinot Noirs cold soaked before fermentation.

This process seldom seems to break its way out of Pinot prison but some believe that this process has the potential to be appropriate for other varietals as well, within a myriad of various styles. With the advent of refrigerated stainless steel fermenters, and the availability of solid CO2 (Dry Ice), this process has become relatively simple to implement. If you’ve made it this far and you’re still nodding your head pretending you know what this fancy cold-soaking thing is, don’t worry, you aren’t alone.

What is Cold Soaking?

Cold soaking, more thoroughly described as “pre-fermentation cold maceration,” is a winemaking process that involves cooling down (usually to around 50-60° F) freshly harvested grapes in the form of must for a selected period of time (anywhere from a few hours to 10 days, but usually around 3 days) before alcoholic fermentation. Not to be confused with extended maceration, which refers to a similar protocol after fermentation, cold soaking allows for aqueous extraction as opposed to the alcoholic extraction you would normally see with extended maceration. This leads to extraction of different compounds, in addition to the liberation of some of the same compounds we would see extracted in an alcoholic extraction, except at different levels.

Of course, a cold-soaked red wine will also see a great deal of alcoholic extraction once fermentation has converted sugar to ethanol, but cold-soaking allows for an extraction balancing act with which the winemaker can more readily control.

What Does Cold Soaking Do for Your Wine?

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Now that we know what exactly cold soaking is, what does it do to the wine? Why are so many winemakers doing it and talking about it? There is, of course, some amount of controversy over whether or not cold soaking is really worth the wait and tank space. The standard idea behind cold soaking is that you get more color out of the fruit (which Pinot is often lacking), without an excessive amount of tannin extraction, which can often happen when alcohol is present. With the color tends to come some degree of an overall increase in the “brighter” flavors, those of raspberry or cherry for example. Or at least that’s story most winemakers will give you when pressed about this cold-soaking thing.

However, some winemakers feel that cold soaking isn’t an efficient or entirely effective method for extraction of color. Winemakers in this camp have found that fermentation temperature, adjusting the vigor of the punch-downs or pump-overs, and the use of enzymes are far more effective at extracting color than letting a wine cold soak. Others swear that their Pinot Noirs end up with rounder, softer tannin structures as a direct result of cold soaking. Some think that this is mostly due to the fact that cold soaking allows you to press off sooner than you would normally, taking the harsh, tannin-rich seeds away from the alcohol and effectively cutting off harsh tannin extraction. All this, while still having had enough initial skin contact to end up with a reasonably strong color and flavor minus the harsh tannins which would otherwise mask some of these flavors. Another huge benefit to cold soaking is that it allows the must to “soak up,” giving the winemaker a more accurate sample to test for pH, TA, sugar content, etc. from which to calculate additions.

Without cold soaking, the must may have some “pockets” of higher acid, for example, than the rest of the must. Acting on this measurement in terms of additions may not be appropriate for the must as a whole. Cold soaking allows everything to mix together so to speak, giving the winemaker a better assessment of what the numbers actually are. Some winemakers also find that cold soaking their wines gives them a greater degree of overall complexity coupled with a more fruit-forward aroma and flavor composition. Of course, nearly all of these winemakers were talking specifically about Pinot Noir, the varietal in which this process is most commonly used.

Best Styles for Cold Soaking Wine

cold soaking pinot noir grapes

So we get why people do it with Pinot, but what about other varietals? Certainly this process, which many agree has had so much of a positive influence on some Pinots, can be beneficial to other varietals and styles of wine, right? Well the answer is unfortunately not as simple as yes or no. Just like anything with making wine, there are so many factors that affect the potential for success with certain methods. Certain varietals, styles of wine, and conditions do not lend themselves well to being put through a cold soak.

There are many aspects that need to be considered before deciding to put a particular wine through a cold soak. Firstly, a winemaker should plan ahead before getting their grapes and decide what stylistic elements they want to impart onto the particular wine they will be making. If a more coarse, phenolic, and less-delicate white wine is desired, perhaps a cold soak for a few hours or days could be preformed prior to pressing. However, a word of caution: many white varietals can become dangerously unbalanced after a cold soak because the amount of tannin extracted, even in a cold soak of a few hours, can overpower the more delicate nature of the varietal itself. In terms of red wines, some varietals just don’t seem to play well with a cold soak. Malbec, for instance, tends to express more of a eucalyptus flavor (generally considered a flaw in Malbec) when cold soaked than it normally would. Merlot seems to be indifferent to a cold soak being preformed, making it potentially unnecessary to put resources into putting a Merlot through a cold soak. Unfortunately, it may take some experimentation to determine if a cold soak is beneficial to a certain wine or not, maybe by splitting a batch into two and cold soaking half of it to compare to a more standard protocol.

Grape Condition and Cold Soaking

grape condition and cold soaking

Perhaps the most important thing to consider before cold soaking is the condition of the fruit after the batch is picked. There is a certain degree of risk that comes with cold soaking, and the potential for serious problems as there is little protection for the wine during the cold soak. Keeping the temperature of the must under 60° F, limiting oxygen exposure to the headspace (which also helps to keep the Acetobacter-carrying fruit flies away from the must), and the use of SO2 at the beginning of the cold soak can contribute greatly to the protection of the batch. However, if a significant amount of botrytis or mildew is present in the fruit, perhaps avoiding the cold soak altogether would be best. While a milliliter of healthy grape juice generally contains several hundred yeast cells, a milliliter of botrytis-infected grape juice is likely to contain several million yeast cells. What’s worse is that most of these yeast cells tend to be of types that are widely known to spoil wine with elevated volatile acidity, off-flavors, stuck fermentations, and other nightmares. To add to the danger, botrytis-infected fruit almost always host an army of spoilage microbes just waiting for an ill-informed winemaker to try and cold soak the grapes they reside in. If there’s any doubt, forgoing the cold soak may be the best option for any fruit which has fungal infections or other problems that may promote spoilage.

Photo Credits
Lead Image , Crushed red grapesLate harvest vine

written by Austin Luse

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