Ashton Lewis is the Master Brewer at Springfield Brewing Company in Springfield, Missouri, as well as the Technical Editor of Brew Your Own. In addition to his technical expertise, Ashton is also BYO’s Mr. Wizard, and has answered many hundreds of brewing questions since 1995. His Wizard columns have been collected into a new reference: “The Homebrewer’s Answer Book,” available online at www.brewyourownstore.com.
There are many beer styles that taste nice using a nitrogen dispense system. I think one of the facts to keep in mind about nitrogenation is that it dampens the flavor profile of the beer. To my palate, the perception of bitterness and hop aroma are reduced and some of the rough edges of beers that are somewhat unbalanced are smoothed out.
In contrast, maltiness is accented. I have used nitrogen dispense for beers from lightly colored golden ales to stouts with various colors and flavors in between. These beers have always been formulated to compensate for the effects that nitrogenation has on flavor.
As with carbonation, temperature affects the solubility of nitrogen in beer. Most beers that are infused with nitrogen or “nitrogenated” are cold during the process. At Springfield Brewing Company we use a blended gas containing 75% nitrogen and 25% carbon dioxide when we nitrogenate certain beers. The 38 °F (4 °C) beer is equilibrated with this gas blend at 26 PSI. One of the things to know about nitrogenated beers, such as Guinness (the brewery who developed this method back in the 1950’s), is that the level of carbon dioxide is extremely low and must be low for the beer to pour properly through the special taps used for nitrogenated beer.
By equilibrating the beer with mixed gas with a low carbon dioxide ratio (20–25% is the norm) the carbon dioxide content will be low (about 1.2 volumes or about 2.5 grams/liter of carbon dioxide) compared to normally carbonated beer.
Beer can be carbonated by simply putting the beer in a keg and pressurizing the headspace and allowing the carbon dioxide to move from the headspace into the beer. Although this process takes a couple of days, it is an easy method to carbonate beer.
Nitrogen, on the other hand, is much less soluble than carbon dioxide and simply pressurizing a keg of beer with mixed gas takes a lot longer to equilibrate. For that reason it is best to bubble the mixed gas through a sintered stone to accelerate the process.
The method we use at Springfield is to first pressurize the headspace of the tank to about 26 PSI with mixed gas, open the gas supply to the sintered “carbonation stone” (in this case it becomes a nitrogenation stone) and then to very slowly bleed gas from the headspace.
The rate at which gas is vented from the headspace equals the rate of gas flowing into the tank as long as the supply pressure and headspace pressure are the same. We use an interval method where we gas for 30 minutes, rest for 30 minutes and then gas for another 30 minutes. We are able to get a 500 gallon (1893 L) tank of beer to the proper condition for dispense after this gassing cycle.
There are three things that are required to serve beer with nitrogen at home: a keg, a supply of mixed gas and a special stout tap. The hardest thing to get is the mixed gas.
When I was in school at UC-Davis, I blended nitrogen and carbon dioxide and used a soda keg as my gas tank. This requires a source of nitrogen and carbon dioxide and is probably not practical at home. The best thing to do is to find a local beverage gas supplier who carries “Guinness gas” and get a small carbon dioxide bottle filled.
I think the best way for homebrewers to start with experimenting with nitrogen is to begin with the classic and that is brewing a dry stout. There is really nothing more exciting than brewing a black ale that when poured has a creamy white head and dancing gas bubbles that take you right back to the first pint of stout you had in an Irish pub.
Once that initial challenge is conquered, the sky is the limit as far as the various beers that will work well with this dispense method.
Andy Tveekrem has overseen all plant operations for the Dogfish Head Craft Brewery in Milton, Delaware since 2004. Educated in brewing at the Siebel Institute, he started homebrewing in 1986 and turned professional in 1991 when, “As Hunter Thompson always said, ‘When the going gets weird, the weird turn pro.’”
The serving method and presentation of a beer are very important. We drink with our eyes first, so if a beer is flat or too foamy or cloudy when it should be clear, then our impression will be negative before we even taste it.
Certain types of glassware have been found to promote certain characteristics of beer, like the Pilsner flute, which showcases the fine carbonation of that beer style. And of course Guinness has done a fantastic job with nitrogen dispense, to the point where the pour is much like a bit of pub theater.
Randall was invented by Sam Calagione here at Dogfish Head a few years ago as a way to showcase dry-hopping. It simply moves the dry-hop addition from the fermentation tank to the point of dispense. It’s great for bars or at festivals because the hops are in a clear housing and people can see the beer flowing through them. It really helps connect people to one of the major ingredients in beer.
If you use a Randall at home, my advice is to be creative and use it as a learning tool. A Randall is ideally suited to home dispense since there is normally a longer contact time with the hops, as opposed to a tavern or a festival where the beer is flowing fast. More contact time yields more flavor.
A Randall is also a great item for experimentation. For example, try taking a pale ale and using different hop varieties in the Randall to see which ones work best with that beer. You don’t have to make a whole brew to try out each variety, just empty out the Randall and refill it with the next hop.
It is also fun to use other ingredients than just hops. Slices of fruit can be used, or spices and herbs — just be sure not to clog up the spaces in the filter element.
Up to now, Randall has been our most exotic serving device, but that can change at any time! Currently we are working on Randall version 2.0, which started as a senior engineering project with a group of Bucknell University students. They redesigned the flow chamber to reduce foaming and enhance flavor extraction. We are still doing our design review and working on a production prototype.