Oxidation, Gluten Free & Keg Pressure: Mr. Wizard


Does adding pre-boiled water to the carboy after I rack my beer help against oxidation (less headspace) or hurt it (risk of splashing)?
Adam Woods
Belding, Michigan

Headspace can cause oxidation, especially in secondary fermenters. Anything that is done to eliminate air helps minimize oxidation. And adding de-aerated water can reduce the odds of oxidation, but the process deserves more than a simple answer. So read on Adam!

In the parlance of commercial brewing this method is typically referred to as high gravity brewing, or simply HGB. The idea with HGB is simple; a brewery can expand the production capacity of a fermenting vessel by brewing high gravity wort in the brewhouse and then diluting the beer post fermentation. The primary motivation to use HGB is monetary since fermentation vessels represent a major expense in terms of capital costs, floor space and labor associated with cleaning, filling and racking. It is fairly common to “extend” a batch by around 25% between the fermenter and package with HBG. There are some breweries who have invested a lot of serious talent into very high gravity brewing (VHGB) and routinely brew lagers with an original gravity in-line with a doppelbock, but the
finished color, aroma and flavor of a pale lager.

The challenge with HGB, and particularly with VHGB, is that yeast are temperamental little critters and generally don’t like it when wort gravity gets too high. In a brewery brewing a large volume of normal gravity beer and a smaller volume of high gravity specialties it is common to pitch yeast from normal brews into specials and then to retire the yeast from the special at the end of fermentation. But when you brew everything from high gravity wort much greater focus is placed on yeast because of the harsher conditions.

Furthermore, the biochemical pathways used for metabolism are affected by wort gravity and this has a direct influence on finished beer aroma. Most brewers utilizing HGB methods want to brew beers that taste very similar to beers brewed at gravity, meaning no dilution, and much of the research conducted by these brewers relates to this particular “magic trick.”

Now onto your question about water . . . boiling water does indeed kill microorganisms that may be living in it and it also decreases the oxygen content. But the oxygen content does not get nearly as low as some may believe because even when water is boiling it is still being exposed to atmospheric pressure and the two variables affecting oxygen solubility in water are temperature and pressure. This means that there is still about 5 ppm of oxygen dissolved in boiling water, and this is far, far greater than the targets of commercial brewers. Most breweries these days have some method for making and storing de-aerated, carbonated water (DCW). At Springfield Brewing Company we make DCW and use it for filter and line presses when we move beer. High gravity brewers use DCW to blend with beer and the oxygen targets in DCW are typically less than 20 ppb. . . or 250 times lower than the oxygen content of boiled water. This means that topping your fermenter up with boiled water is actually not a good method of controlling oxidation.

Most systems used to produce DCW use gas flushing under vacuum or membrane diffusion. It is possible to strip oxygen from water by bubbling nitrogen into it. This is what we do at Springfield Brewing Company and empirically I know that it works, but since we currently do not own a dissolved oxygen meter I do not know the oxygen content of our homemade DCW. I do know that when we began making DCW that oxidized notes in our beer following filtration (our filter runs begin and end with water presses) disappeared.

To sum it up, this method you propose using does work, but you need to use water that is de-aerated by a better means than boiling. It also can be used to stretch your volumetric yield but you need to plan for this and brew beer that is concentrated and intended for later dilution.


Can 3-gallon (11-L) batches of beer be fermented in 5-gallon (19-L) carboys — primary and secondary?
Pat Fitzwater
Bath, New York

If you brew a 3-gallon (11-L) batch and ferment the beer in a 5-gallon (19-L) carboy you will be just fine with respect to the oxidation issue, and the beer will ferment without other issues. In fact, having enough headspace to prevent foaming over during fermentation is the norm in commercial breweries where foam spewing from the top of the fermenter equals beer loss. This costs money and businesses are not keen on seeing money flowing from tanks. However, many breweries see a benefit from having trub stick to the fermenter sides and top, and in some cases false roofs are installed to help skim this bitter trub from the beer. This is one reason that brewers who use open fermenters skim their fermenters.

When fermentation is over you need to be careful not to oxidize the beer during racking. Transferring 3 gallons (11 L) of beer from a 5-gallon (19-L) fermenter into a 5-gallon secondary fermenter, a clean carboy for example, is a practice I would perform with great caution. Since yeast activity is very low at this stage of the process you can have real problems associated with air pickup.

In all honesty, racking beer into a secondary is a practice frequently omitted by home and commercial brewers because it is often times totally unnecessary. If you are racking beer onto something, like fruit, then the practice has merit. Or if you plan on prolonged aging and want to remove the beer from yeast it also makes sense. But for most beers with a two to three week total process time racking into a secondary fermenter does not do much.

Aggressively purging carbon dioxide in the carboy prior to racking is one way to greatly minimize air pick-up. The best way to do this is to put a tube all the way to the bottom of the secondary and slowly flow carbon dioxide into the vessel so that it creates a layer at the bottom of the vessel and pushes the air through the top. Another method is using a keg for your secondary; kegs can be filled with water and completely filled with carbon dioxide before filling. For the super cautious brewer, this alternative method allows racking to occur without future worry!


My good friend is gluten free and I have been brewing for some time now and we have talked about making a gluten-free beer for him to enjoy. My local homebrew shop sells gluten-free extract but I am looking for more to add. He once tasted a black IPA and enjoyed it a lot. What are things I can add to make a better beer? Would soaking uncrushed black or chocolate malt in cold water result in glutens? Is lactose sugar okay to use or will there be glutens left? what are some other grains to add or roast myself to add some complexity?
Mike Dellemann
Stevens Point, Wisconsin

Celiac Disease is an immune reaction to certain gluten proteins found in wheat, barley, rye and oats. This means that when a brewery brews a beverage specifically for this group of people great caution must be taken to prevent these special gluten-free beers from being contaminated by the normal brewery environment. This is not an easy thing to do in a commercial brewery since malt conveyors, mills and hoppers are not typically cleaned like other brewing equipment because dry handling equipment has different cleaning requirements than equipment used to handle liquids. At home things are much easier to control.

And this begins with yeast. If you buy liquid yeast starters there is a chance that the starter could contain gluten proteins because wort is a great growth media and brewers like pitching yeast grown in wort. Even dried yeast can be an issue since it is also grown in some media. In order to be sure you begin with gluten-free yeast, talk to your yeast supplier to be sure that it is gluten free. Or, you can grow your own yeast by beginning with microbiological plating, followed by propagation in gluten-free wort.

Gluten-free extract is a great way to make your wort since the suppliers of these extracts have really done the hard part. The most common grain used for gluten-free beer is sorghum and the gluten-free extracts I have seen are predominately made from sorghum. Other common gluten-free ingredients include honey, sugar, rice and maize.

The challenge that is often faced is adding colors and flavors to sorghum malt for specialty beers. All special grains made from wheat, barley, rye and oats are off-limits, and cold extraction methods like you describe do not make them okay to use.

Ingredients like coffee, chocolate, fruit, peppers, spices, molasses, roasted pumpkin and oak would be easy to use to augment a relatively bland sorghum extract base. A chipotle porter could be made using ingredients like chicory and cocoa as a substitute for roasted malt/barley and the beer further flavored with chipotle peppers for richness. You could also try brewing some sort of high gravity beer, darken it using black treacle, gently spicing with something like black cardamom powder and then age it on oak (or with oak chips) to add another layer of complexity.


I bought a keg system along with a CO2 tank and two used 5-gallon (19-L) soda tanks. I rebuilt both tanks using new o-rings and valves. I have made four batches of beer since June, two lagers and two ales. The ales are always carbonated, but the lagers lose their carbonation over time. any suggestions?
Frederic Dreves
Traverse City, Michigan

I think that there is nothing wrong with your equipment or beer. I think the problem is with the way you are setting up your dispense rig. Specifically, I think that your carbon dioxide pressure is too low for your lagers.

For the sake of argument, I will assume that your lagers are carbonated to a level of 2.6 volumes of carbon dioxide. Why do I assume this? Because this is the carbonation level of most lagers. This corresponds to about 13.5 psig at 40 °F (4.4 °C).

As for the ales, this is where I am guessing, and my guess is that you carbonated your ales lower than your lagers, maybe around 2.45 volumes or 12 psig at 40 °F (4.4 °C). The problem is that you have two kegs of beer stored in one refrigerator and connected to the same gas tank. If the tank pressure is adjusted to maintain the carbonation level of your ales, then your lagers will slowly lose carbonation during storage. Likewise, if your gas pressure is set for your lagers, the ales will gain carbonation over time. You can carbonate your ales and lagers to the same carbonation level so that you don’t need any more equipment. Or, you can set up a gas manifold with more than one line regulator and adjust the pressure on the keg to match its carbonation level.

Issue: May-June 2012