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When 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.

View of "Gassing Bell" used in the winery. A gassing bell equipped with a diffuser stone allows for slow and gentle gas application over a wine surface.

Preventing Oxidation

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.

A magnified view of a sparging stone used in the winery. The irregular texture provides many channels that gas must flow through as it exits the stone. When blanketing, this is effective by removing energy and slowing down the gas to provide a gentle flow onto the wine surface. When sparging, this helps in controlling the surface area where the gas exits the stone.

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.

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