Aeration & Mash Hopping: Mr. Wizard


I have been trying to come up with an easy and cost-effective way to get good aeration in my fermentations. I recently came across a device called an Oxygen Concentrator, which takes regular air and concentrates the oxygen for use in the medical industry. There are models for home use priced in the $500-$1,200 range. Could these devices be used for wort aeration in place of buying the red welding bottles at home improvement stores or the medical grade bottles?
Darin Ebberson
Pasco, Washington


The imagination of the homebrewer never ceases to amaze me. Using an oxygen concentrator to produce oxygen for wort aeration certainly is a creative way to tackle this particular brewing process. I must admit that I was not sure how these devices function. My guess was that the oxygen concentrator uses a membrane filter to separate nitrogen from oxygen, basically the opposite of how nitrogen generators operate, and did some reading to check my guess.

It turns out these devices use a zeolite medium as a molecular sieve to separate nitrogen from oxygen. The resultant oxygen is blended with air to control the oxygen content of the gas delivered from these units. One major benefit is that they replace bottles of pure oxygen, which are heavy, have to be re-filled and are potentially dangerous since oxygen is just a wee-bit combustible. So far, this device is looking like something that a brewery may find useful.

You state in your question that you are looking for an easy and cost-effective method to oxygenate wort. While this device may be an easy source of oxygen, plug it in, turn it on and out flows oxygen, I am having a hard time considering a $500 investment (minimum) in this device cost-effective. If this seems like a reasonable investment, go for it and let us know how it worked. But if you really would rather spend $495 on ingredients and $5 on a wort aerator, keep reading.

In the old days before high-gravity brewing (strong beer diluted with water prior to packaging) and commonplace double IPAs, brewers would aerate wort with air. Indeed, a significant volume of the world production of beer relies upon air for aeration, not bottled oxygen. The solubility of oxygen in wort decreases as wort strength increases, and it also decreases when air is used instead of oxygen. The use of oxygen for aeration makes sense for stronger beers. But even for high-gravity worts aerated using air, there is sufficient oxygen for yeast to produce the sterols and unsaturated fatty acids needed for cell wall synthesis. Yeast biochemists and practical brewers know that increasing the oxygen concentration in high-gravity worts can improve fermentation rate and the health of yeast cropped from these fermentations, but very few will argue that wort must be oxygenated. At Springfield Brewing Company we use air for all of our wort aeration needs, independent of wort strength, and we brew beers ranging from 11-24 °Plato (1.044 – 1.100 SG).

If you do choose to add oxygen to wort, you do need to be aware that excessive oxygen can cause stress to yeast cells, increase the concentration of some fermentation products such as acetaldehyde and sulfur, and can also cause fermentations to become stuck. Commercial brewers who add oxygen to wort often measure the dissolved oxygen to prevent adding too much. A common target level is 15 mg of oxygen/liter.

The type of aeration device used in most modern breweries utilizes a Venturi nozzle to aid in gas transfer. These devices rely on the reduction in pressure that occurs when liquid flow is accelerated through a restriction in a pipe to bring gas into the wort stream. In a commercial brewery these devices are supplied with dry, compressed air or oxygen that is pushed through a sterile filter en route to the Venturi nozzle and they work extremely well.

You can build your own Venturi aeration device by purchasing a hose-barb tee. Hook one end of the tee to the outlet of your wort cooler, one end to a cane extending to the bottom of your carboy and leaving the other end (pointing upward) open to the atmosphere. The open end is your gas inlet and what happens when wort flows through this contraption is that air is sucked into the open end as the pressure of the liquid is reduced as it flows through the tee. Of course, atmospheric air is not really what most brewers want in their wort. The cheapest way to filter gas is by using a cotton plug jammed in the open end of the injection tee. This whole thing can be made for $5 or less. I will leave the remainder of this project to our DIY desk, but suffice to say, this baby works. I built something like this while I was a graduate student in the brewing program at UC-Davis and never had any problems with contaminated beer (I am assuming some readers may be wondering if the cotton plug actually works).

I do like your creative solution to wort aeration and see nothing at all wrong with the idea of bringing in an oxygen contractor to supply your oxygen. You could even hook the concentrator into the tee I describe, but I honestly do not think you will see marked improvements in your beer. And this advice is coming from a brewer who has been preaching the benefits of proper wort aeration in the pages of BYO for the last  20+ years. If it were my money, I would build Ashton’s cheapo aerator and invest the remainder into ingredients or other brewing tools.

I have encountered some debate on a beer science/homebrewing question that has a couple of us split. I harvested some homegrown Columbus hops this year and was thinking about using them in a mash hop to help bring a lot of hop aroma and flavor without having a significant amount of trub and wort loss in the boil. I got this idea from reading Mitch Steele’s book on IPAs. However, one of the people I brought this up to said it would be a waste of my hops because all of the aroma/flavor components in the hops will just be boiled off.

Do you have any experience with mash hopping beers? What would the science suggest about using hops in the mash? Thanks for your insight!
Keith Bachman
Ozark, Missouri


Thanks for the good question, Keith. I have always thought that the notion of adding hops early in the process, either as mash additions or pre-boil additions to the kettle, in an attempt to improve aroma retention is completely counter-intuitive and inherently illogical. Increased exposure to high temperature will simply lengthen the time for precious hop oils to volatilize and serve as aromatherapy for those around the brewhouse during wort production, so the argument against this method goes. I have never added hops to a mash, and don’t have any first-hand experience with this method. Nothing I have read about this technique has persuaded me to want to experiment with mash hopping because the purported benefits seem pretty marginal.

The basic argument in favor of mash hopping is that flavor components from hops are extracted during mashing that are not extracted in the kettle because of pH differences between the mash and wort. According to this argument the flavor of beers that have been mash hopped are indeed different from those that have not been mash hopped, ergo the method adds something to beer flavor not achievable without the method. Another argument in favor of the method is that hop oils oxidize, become less volatile in the boil and remain in the beer to contribute to beer flavor. I think these arguments are interesting enough that, if you would like to see for yourself, you should brew two batches of the same basic beer with the only difference being the use of mash hopping. You can conduct this experiment, host a blind tasting somewhere large enough for the members of your club … I am thinking that Springfield Brewing Company may want to host your tasting … and determine what it did to your beer.

Many brewing techniques address issues related to process efficiency. Let’s consider a brewery that uses a lot of cone hops and a hop back for hop removal. If the hop cones are not sparged following separation, wort is lost when the hops are discharged from the hop back. When the hops are discharged from the hop back, they need to be somehow removed from the brewery. One way to deal with both of these issues is to move the hops contained in the hop back into the next mash of the day. This addresses the concern over wort loss and allows the hops to be removed with the spent grain. Voila, problem solved.

Do these methods make any sense and are there similar processes used by brewers? The answer to both questions is yes; it is common practice in many breweries to transfer trub removed from the whirlpool after use to the lauter tun. This reduces wort loss associated with trub and reduces the volume of effluent sent down the drain.

My conclusion on this topic is that mash hopping may have historical ties to attempting to deal with a waste stream. There is a huge amount of anecdotal information on brewing forums about this technique. Some brewers who have used the method believe it is beneficial and others believe it does not do anything other than use expensive hops to contribute nothing identifiable. Looks like you need to conduct an experiment and develop your own opinion about this technique!

Issue: December 2013