Aeration on the Cheap
by Steve Marler
Just as your partner breathes heavily during sex, somemore than others, yeast needs oxygen to grow and reproduce.Yeast grows and reproduces first, and then they begin eating sugar, and excreting alcohol and carbon dioxide. Problems such as long lag times, stuck or incomplete fermentation, or excessive ester (fruit aroma and flavor) production, can be associated with a lack of dissolved oxygen in the wort. During boiling most of the oxygen is driven out of solution. Oxygen must be added to cooled wort. The amount of oxygen in wort is a function of temperature and specific gravity. The lower the specific gravity and colder the wort, the more oxygen will be able to enter into solution.
Yeast needs 8 to 16 ppm of oxygen to properly do their thing. So how do we replenish the wort oxygen? There are many techniques available. However like many brewing processes, the more effective the technique the higher the cost.
The most effective, and expensive, technique is injecting oxygen into the wort. To accomplish this you need an oxygen tank, regulator, and aeration stone. Most home brew stores carry The Oxynater™. It is a ready-made apparatus for diffusing oxygen into wort and includes a cylinder of oxygen, gas regulator, tubing and a stainless steel diffuser. Most home brew stores carry simple regulators with a 1! 4 -inch barbed fitting that that screw onto disposable oxygen cylinders. They also carry stainless steel diffusion stones. If your local home brew store does not carry disposable oxygen cylinders, you BURP News September, 2012 Page 5 can find them at most hardware stores. Injecting oxygen for about 5 minutes will provide up to 25 ppm or oxygen.
Shaking or Agitation is widely used by new brewers, but is the least effective method of aeration. If the beer is in a carboy, this can be accomplished by putting a piece of foil over the mount of the carboy and rocking it back and forth so that it sloshes. If fermenting in a bucket, you can use a sanitized stainless steel whisk to whip up the wort. If you want to save your arm, could buy and sterilize a painter stirrer and attach it to your drill. You can buy a stirrer for as little as $5.00. With any of these methods you need to build up a couple of inches of foam. This is hard work if shaking or whisking by hand. If done properly you may get up to 8 ppm of oxygen.
Splashing can be a more effective technique than shaking or agitation. In the winter, when I am able to cool my wort to the proper temperature, I utilize this technique. You can use this technique if you run cooled wort through a tube from kettle or counter flow chiller into the fermenter. Attaching a clip or other device (such as a Fermentap Siphon Spray – $4.00) to the end of the tubing will cause the wort to spray and splash as it enters the fermenter. A less effective method is to transfer the wort between two sanitized carboys or buckets splashing as practical. You will need to do this at least five or six times. Pouring the wort through a sanitized wire mesh strainer can also increase splashing during the wort transfer process. As with shaking or agitation, you will need to build up a couple of inches of foam. Depending on how you do the splashing, this method will get you 8 ppm to 8 ppm sustained oxygen. The Dawson Tube is a modified splashing technique that is both inexpensive and effective. I call it the Dawson Tube because Bob Dawson, who mentored many of us long time BURP members when we started home brewing, showed me this device. The Dawson Tube is a copper tube with wholes drilled into it, on an angle, which fits onto the end of a siphon hose. As the cooled wort flows from the kettle or counter flow chiller through the Dawson Tube, it picks up air through the holes and also causes splashing in the fementor. To make one, get a short piece of copper tubing with an outer diameter equal to the inner diameter of the hose. I used a semi-ridged copper toilet water supply line that I picked up at my local hardware store. Using a 1/16 inch drill bit, drill a series of wholes (on an angle in the direction of wort flow) about ½ inches apart down the length of tube. Clean and sanitize the Dawson Tube and connect it to the end of the siphon hose. I am not sure how many ppm of oxygen you will get, but probably at least 8 ppm sustained is my guess.
Injection of air into wort can be accomplished more cheaply than injecting oxygen by using an aquarium pump (or other air compressor). If using an air pump it is recommended that you filter the air so that only clean air goes into the wort. A HEPA (High Efficiency Particulate Air) filter with a .023 micron sized filter, or a filter improvised from cotton balls wetted with alcohol is recommended to keep the air as contaminant-free as possible. Many homebrew suppliers carry air pumps, filters and diffusers for this method of wort oxygenation. For example, My Local Homebrew Store carries a kit that includes the pump, aeration stone, and filter for $34.99. They sell the pump separately for $14.99 and sell two sizes of diffusion stones for $14.99 and $29.99. Using an air pump will give you about 8 ppm sustained. For as little as a couple of dollars for a piece of copper tubing, to a manageable $40.00 you can make sure your
yeast have plenty of oxygen, improve fermentation, and improve your final beer.
References Lutzen, Karl F. and Mark Stevens. Brew Ware: How to Find, Adapt & Build Homebrewing Equipment. Canada: