Either carbon dioxide or nitrogen can be used to provide effervescence to beer, but the two substances are very different in how they react with beer under pressure. Carbon dioxide is highly soluble in water-based liquids (i.e., beer) whereas nitrogen has a much lower solubility. Thus, a keg, bottle, or can pressurized with carbon dioxide will have much more carbon dioxide dissolved in the beer compared to gas dissolved in a nitrogen-pressured keg, bottle, or can. When nitrogenated beer is opened or tapped, the bubbles of nitrogen that come out of solution are much smaller than the bubbles of carbon dioxide that form from a carbonated beer. This has some noticeable effects on the appearance and mouth-feel of the beer.
The nitrogenation process will vary somewhat depending on the volume of beer being produced. Nitro beer gas can be provided from gas cylinders (i.e., Dewars) or a nitrogen generator.
Nitrogen generator can be used to produce nitrogen gas for beer. Nitrogen generators operate on compressed air by reducing the percentage of oxygen in the air to solely deliver nitrogen to the required application. Nitrogen systems for beer have small footprints, and some, can deliver up to 99.5 percent pure nitrogen with adjustable flow rates pressure.
Types of Nitrogen Generators. There are two main types of nitrogen generators, hollow fiber membrane and pressure swing adsorption. Hollow fiber membrane nitrogen generators operate by selectively allowing nitrogen gas to flow through the fibers of the membrane. Oxygen and other contaminants are then released back into the atmosphere through a port in the generator.
Other Uses of Nitrogen
In addition to nitrogenating beer, nitrogen is commonly used throughout the brewing process because of its inert characteristics. Nitrogen flushing is done to eliminate gaseous impurities (carbon dioxide and oxygen) from brewery vessels inhibiting the onset of undesirable oxidative reactions. By using compressed nitrogen for cleaning, brewers can ensure residual mash, wort, and beer is removed. Leftover beer and ingredients can oxidize, polluting the next batch that goes in the tank with a sour flavor.
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