Bottling from a keg

Kary, let me begin by stating for you and other readers that I absolutely despise oxidized beer. When I was a student at UC-Davis (located down the hill from Placerville), one of the things Dr. Michael Lewis instilled in his brewing students was a keen awareness of oxidized beer flavors and a vehement opposition to them. After all, oxidation is what limits the shelf life of most beer in the world. While it is true that some beers expire early because of microbiological problems, the real shelf-life issue in modern brewing is oxidation.

So this sounds like a big brewer problem because commercial beer sits on the shelf waiting to be purchased, right? Well the truth is that beer oxidation happens very quickly and excellent beer can quickly be ruined by oxygen. Dispensing carbonated beer from a keg into a bottle and capping it is not a good method.

When I first began brewing at Springfield Brewing Company our restaurant management team at the time insisted that we sell growlers. I thought I hated growlers as much as any brewer back then, but my negative feelings swelled after dealing with them for a few months.

In the early days we would fill growlers the “traditional” way by hoisting one of these inelegant jugs up to the tap and filling it with beer until the foam was displaced and the whole jug was full of beer. This process is just a little bit wasteful! After filling, a screw cap is applied and the growler is hauled home for quick consumption. I don’t know about other brewers, but I never was proud of the way my beer tasted from a growler because it was oxidized, even within a day or two of filling. Keep in mind my palate is biased to detect and dislike oxidized beer!

So we quickly began counter-pressure filling growlers to combat oxidation and also to have growlers pre-filled so that they were ready for sale. This helped a lot until one day we blew up a growler during the pressure cycle of filling. When I called the company who marketed the containers we were purchasing as “beer growlers” I learned that the containers were not rated for pressure. I guess the fact that beer is carbonated did not ring a bell with this company that pressure is associated with carbonation. In any case, we quickly discontinued using growlers and transitioned into normal beer bottled with crown caps.

For the record, there are growlers intended for pressure. I like the appearance and convenience of the large swing-top “siphons” from Germany, but these are comparatively expensive and I was looking for a reason to discontinue the use of growlers and was not in search of a suitable container. Growlers also have to be cleaned when brought in for refilling and this presents an entire separate set of logistical challenges for the pub brewery.

So once again we wanted to package beer in the best way possible to prolong the period over which our beer tasted fresh. And once again we were focused on minimizing oxygen in our packages. When beer is filled into a bottle there is indeed a gas space above the beer, but this gas space does not have to be air. If you could fill the beer in such a way to ensure an even gas space of carbon dioxide above the beer after capping, things would be great. Fortunately, this problem is easily solved by intentionally foaming or “fobbing” the beer after filling and before capping. By capping on foam there is no headspace for air to accumulate in and the foam collapses after filling and leaves a nice clean headspace of carbon dioxide. This method has been used for decades as an easy first line of defense against air pick-up at the filler.

Filler technology has progressed and today’s modern fillers are amazing, both in terms of speed and performance. While no method totally eliminates oxygen from the package, modern filling technology comes pretty darn close. State-of-the-art filling technology today is synonymous with double, pre-evacuation fillers. These have been available for about twenty years now and work by pressurizing the bottle with carbon dioxide, evacuating the gas using a vacuum pump and then pressurizing once more prior to filling.

Once a system is in place to really minimize oxygen pick-up during filling the last measure of precaution is to attempt to mop up the small amount of oxygen that is introduced during filling. This is where the oxygen absorbing liners used on beer caps comes into play. These caps do work well, but they are not intended to make up for deficiencies in the method used to fill bottles. Rather they are used to make good filling practices using the latest filling technologies even better.

I can understand the desire to have bottles of beer because you can easily transport them. Your method begins with kegged beer. I suggest leaving your beer in the keg. Kegs can be purged prior to filling and are excellent packages. If you really want to take some beer from your keg to another location and do not want to get into counter-pressure filling, wait until the last minute to move your beer from keg to bottle. You can use a flexible hose to connect the tap on your keg to a long fill-tube (preferably made from stainless steel or a small diameter beer line). If you fill from the bottom of the bottle and control foaming by lowering your keg pressure by a few pounds during this process this method will work well as long as you consume the beer shortly after filling.

Response by Ashton Lewis.