W hen one thinks about winemaking, gasses may not be the first item that comes to mind. However, there is a small family of gasses that play an important part in the winemaking process. Gases can be used to transfer (push) wine, to protect wine and to adjust the level of other gasses in the wine (add or remove). You will often see high-pressure cylinders of gasses around the wine cellar. Some of these gases classify as what is called an “inert gas,” meaning they are extremely non-reactive. This is great because that gas will not react with the wine or any other gas. Other gasses are used simply for their physical or chemical properties. Before discussing gas use in the winery, it must be noted that many gases can be extremely dangerous to work around and all OSHA guidelines must be strictly followed. Gases can be particularly dangerous in confined spaces.
It is fairly well-known that oxygen needs to be very regulated in the winemaking process. Simply put, inert gases can be a line of defense from too much oxygen in your wine. One of the more common places where this is implemented is when a wine storage vessel is not full, leaving a headspace void above the wine. Removing oxygen in this headspace decreases the chance of oxidization or spoilage by bacteria or yeast. Oxidation in the case can be prevented by filling the headspace with a specific inert gas. Removing (or specifically, “displacing”) the oxygen from the headspace with another gas is casually known in the industry as “blanketing”, or sparging. This refers to the action of using another heavier gas to create a layer, or blanket, above the surface of the wine that protects the wine from the lighter oxygen molecules above this blanket, thereby protecting the wine from oxygen dissolving into the wine. In this case, the way one dispenses the gas to the tank is critical. It is recommended to do so with a method that de-energizes the gas as it flows from the dispensing tube. If the flow of gas is too rapid, turbulence will be created in the headspace of the tank and mix the headspace gases rather than creating a smooth layer. Also, always note the size of tubing and pressure used when sparging. One should always calculate the volume of gas needed for an effective blanket rather than simply relying on a rule of thumb or you may have insufficient volume to protect the tank.
Sparging can also refer to the act of displacing the entire volume of a vessel and replacing it with another gas. This can be for tanks, but it is most often seen at the bottling line. Here, wine is transferred into the bottles to be filled, but the winemaker would not want the wine to absorb any additional oxygen during that delicate process. Instead, one would displace all atmospheric air in a bottle and replace it with another gas, such as nitrogen, before filling the bottle with wine. Therefore, when the wine is pumped into the bottle, there is no oxygen to come in contact with the final wine.
Nitrogen, carbon dioxide, and argon are all options for this type of sparging. Technically speaking, Argon is the only truly classified “inert” gas of these three, but they can all be applied with slightly different outcomes. Depending on specific use, they have advantages and disadvantages. Cost, molecular weight, effectiveness, and the end goal are all factors of making a choice of which gas to use.
Adjusting Levels of Gases in Wine
Carbon dioxide is an important component of wine, especially white wines. Dissolved carbon dioxide can impact the flavor, freshness, texture or acidity of a given wine. It is a naturally occurring byproduct of fermentation that normally stays with the wine during aging. However, the level of carbon dioxide may need to be adjusted based on the winemaker’s preference. One can do this by sparging the wine with another gas (in this case, sparging would be defined as bubbling a gas through the wine). For example, if one bubbles carbon dioxide through the wine, it would increase the level of carbon dioxide in that wine. The opposite result, reducing carbon dioxide, could be obtained by bubbling nitrogen through the wine. This result is seen because the bubbling creates a partial pressure between the introduced gas and the dissolved gas—and the difference of the partial pressure causes the dissolved gas to leave the solution.
An Overview of the Gases
Nitrogen is a gas that often used in wine production. It comprises nearly 80% of the atmosphere that we breathe, and is a relatively light gas with a molecular weight of 28.0134 g/mol. As an inert gas, it will not dissolve in the wine and produce different or off flavors. Nitrogen is also considered an inexpensive gas. However, because nitrogen is light and has the same density as atmospheric air, it will have a minimal amount of a blanketing effect. Without a heavier “blanket” in the headspace, the chances of oxygen getting back into it are higher. This will require more sparging and higher use of nitrogen creating more work and frequency of use. As mentioned, nitrogen is used to push out oxygen in headspace. It can also be used during sparging for bottling, keeping tasting room bottles fresh, and for transferring wine where pressurization is required, such as using a “Bulldog” racking wand.
Carbon dioxide is also a common inert gas used at wineries. With an atmospheric make up of about .04%, its molecular weight is 44.01 g/mol. Because its molecular weight is heavier, it creates a greater “blanket” when introduced into a container’s head space. The outcome of a heavy blanket results in less chances for oxygen to enter and spoil wine. With more blanket coverage and inexpensive price, it is a popular choice to purchase for the best return. However, because carbon dioxide is soluble in wine, it will lose that protective blanket over time. It can also cause a spritz, or effervescence in wine, which may be undesirable. The most common use of carbon dioxide is for temporary blanketing. The use of solid carbon dioxide, as known as dry ice, is very popular and especially beneficial during harvest. Dry ice will sublime into gaseous CO2 and maintain a blanket over grapes or must to reduce oxygen levels. It can also keep grapes cool to prevent spontaneous fermentation.
Argon is a true inert gas and has an atmospheric makeup of about 1%. With a molecular weight of 39.948 g/mol, it is a heavy gas that can be useful in wine production. The heavy molecular weight serves as a thick cover for blanketing wines in all areas of wine production. Argon is not soluble in wine and does not present the issue of dissolving, and therefore provides a longer-term blanket protecting the wine. According to research and a blind tasting panel, wines sparged with noble gases, such as argon, have improved shelf life, color, flavor, and aroma in comparison to those sparged with nitrogen. (Allen, Don). Even with the advantages of argon, it is not budget friendly.
As you can see, gas management is particularly important in the winery and has many applications. And when choosing a gas to use, one has several choices that would depend on the particular objective with the gas and other factors, such as available budget. Ultimately, one needs to be very aware of the details of each gas because they are all unique.