Low Oxygen Brewing-Summarized for the Homebrewer
Low oxygen brewing is common practice for breweries in Germany and other places around the world. This style of brewing reduces or eliminates oxygen throughout the entire brewing process, from doughing-in to packaging. In their paper entitled, “On Brewing Bavarian Helles: Adapting to Low Oxygen Brewing”, the team at the German brewing forum purports that, “it takes less than 1 minute of oxygen exposure in excess of 1 ppm to completely rob the beer of the fresh malt flavor”.
For the homebrewer, that means some serious thought needs to be put into our brewing systems and procedures before we can hope to attain dissolved oxygen levels as low as that.
Most of us homebrewers will not go out and purchase any expensive new equipment to accommodate this new style of low oxygen brewing (new to us at least). But, from what I have read, the only purchase you will have to make is to get rid of or sell your old copper immersion chiller or copper plate chiller and purchase stainless steel. Apparently copper, iron, zinc and manganese accelerate the oxidation of malts.
These reactions involve way too much chemistry for me to include in this article, so if we take the German brewing forum team’s word for it, then we need to eliminate all copper from our brew systems if we want to brew with the low oxygen brewing method.
Realizing that we homebrewers are as a group, cheap, we are also perfectionists when it comes to making beer. We want to brew the absolute best beer possible within the limitations of the equipment and processes that we can employ as homebrewers.
So, with that in mind, I don’t think replacing an IC would be overly expensive if we knew we could brew much better malt forward (typically German style) beers.
Most of the changes homebrewers will have to make to employ low oxygen brewing are easily achievable with only minor alterations to procedures and equipment.
I have not had a chance to verify any of the information in the paper, but from what I’ve read, other brewers have successfully recreated the results.
To me the effort to eliminate or reduce the amount of dissolved oxygen in our brewing process is definitely worth doing as we all know about oxygen’s effect on shelf life and staling of our beers. Employing the LODO brewing method will, however, add some time to an already long brew day.
I’ve summarized some of the main points in the article that are relevant to homebrewers in the table below:
- The major problem for homebrewers wishing to try low oxygen brewing is that the malt is already oxidized before we finish doughing-in because our strike water is saturated with oxygen. Our cold tap water or the cold water coming out of our RO system is saturated with 8-12 ppm of dissolved oxygen.
- If you can smell malt aromas at any time during your hot-side process (while your wort is above 140°F or 60°C) then those aromas and flavors will no longer be available in your finished beer. Using low oxygen brewing will result in your mash and boil having much less of the malt aromas you are used to.
- At typical mash temperatures of 145-160°F (63-71°C), the solubility of oxygen in water is about 4-5 ppm.
- Pre-boiling and rapidly chilling your brewing water will reduce the dissolved oxygen level to less than 0.5 ppm.
- With current homebrewing procedures, doughing-in will add approximately 1-3 ppm of dissolved oxygen to your wort.
- Between 1-2 ppm of dissolved oxygen will diffuse into your wort from the atmosphere per hour.
- 1 ppm of dissolved oxygen present at any time during the “hot side” of your process is enough to remove the fresh malt flavors from your beer.
- The process of hot-side oxidation (HSO) results in both the loss of malt flavor and the creation of staling compounds in your finished beer.
- HSO in low oxygen brewing occurs many times faster for the homebrewer compared to a commercial operation due to the increased surface area exposed to oxygen. A typical commercial brewery’s surface area to volume ratio (of 26,417 gallons or 1000 hectoliters of wort) is 20 times less than a homebrewer’s normal 5 gallon batch size.
- HSO in the mash will begin within seconds and the peak reactions will occur within the first 30 seconds to 1 minute after doughing-in. This is why it is so important to get the dissolved oxygen level in your strike water as close to zero as possible prior to adding your grain.
- In commercial breweries in Germany and other places around the world which use the low oxygen brewing method, the grain is added first and the hot strike water is introduced from below. For homebrewers this may not be possible, depending on the design of your brewing system.
- Normal homebew kegging procedures will pick up around 0.8-1 ppm of dissolved oxygen (DO). So, it’s important to use the recommended purging procedures in step 18 below.
Low Oxygen Brewing Steps for the Homebrewer
If we as homebrewers wish to use low oxygen brewing, then to remove oxygen at the homebrew level means that we must eliminate all sources of dissolved oxygen and oxidation accelerants (ie. Copper) as well as employ the use of oxygen scavengers.
I’ve gone through the article on low oxygen brewing and pulled out the steps we as homebrewers can easily employ to make better German style beers using the low oxygen brewing method:
1. Remove the oxygen from your strike water by pre-boiling the strike water immediately before use by boiling it vigorously for 5 minutes and quickly chilling it down to strike temperature. An immersion chiller (IC) works best but using a copper IC is not recommended because the copper accelerates oxidation of the malts.
2. Add Sodium Metabisulfite (SMB) (not potassium metabisulfite) as an oxygen scavenger to control the ingress of oxygen. Excess sulfites will be consumed by the yeast during fermentation and the final level of sulfites in your homebrew will be consistent with those in commercial German beers. FYI: Sulfite levels in most commercial beers that come from normal fermentation processes will typically be in the 10-15 ppm range.
3. Use reverse osmosis (RO) water, adding enough calcium chloride to produce 30-50 ppm calcium. In your water addition calculations, account for the fact that each mg/l of SMB will add 24 ppm of sodium to your water. The same concentration will also add 76 ppm of sulfur compounds in the form of sulfates, sulfur dioxide, and bislufite. The amount of sulfate added is more difficult to calculate because it depends on the amount of oxygen introduced and subsequently removed by the oxygen scavenger.
4. The team at the German brewing forum recommends that you add 100 mg/l of SMB in the mash water and 10-15 mg/l of SMB in the sparge water for low oxygen brewing.
The amount of sodium and sulfates added from the addition of SMB will depend on the ratio of mash water to sparge water in your recipe. Be aware that this is a starting volume of SMB and will need to be adjusted as you brew subsequent batches. If you notice excess sulfur in your finished beer, reduce the addition of SMB in your next batch.
Also be aware that different strains of yeast will utilize or tolerate sulfate levels differently, especially when comparing lager yeasts to ale yeasts. Experimentation will be needed to optimize the amount of SMB added to your system.
For those who are metrically challenged, the GBF team has written a spreadsheet for the Sparge and a spreadsheet for the Mash to calculate the correct amount of SMB to add in both metric and gallon units.
5. If you brew with a no-sparge process, reduce the amount of SMB from 100 mg/l to 55 mg/l.
6. If you cannot get powdered SMB, a campden tablet will supply 440 mg of metabisulfite per tablet. Campden tablets are readily available at all homebrew and winemaking supply stores.
Crush the campden tablets if using them, or add the powdered SMB to the strike water and let it set for no more than 5 minutes prior to doughing-in to allow the metabisulfite to scavenge the available dissolved oxygen.
As a rule of thumb, it takes about 5 ppm sulfite to scavenge 1 ppm of oxygen from your water.
7. If you cannot add your grist to an empty mash tun and introduce the strike water from below (which many of us won’t be able to do), then add the strike water first with as little splashing as possible then add the grain from above slowly and while gently stirring.
It is critical not to add the grist too quickly or stir too vigorously which will aerate the wort. If your grains are floating on top of your strike water, then you have air trapped in your grain that will be incorporated while you dough-in. Too much oxygen introduced here will not only oxidize the malt but also consume a large amount of the SMB in the strike water.
8. Mash for as little time as possible. Check for starch conversion by draining from below. A good DIY project to reduce the head space and thus the oxygen above the mash would be to design a mash cap or a lid that can sit just above the top of the mash. If nothing else, how about laying plastic wrap such as Saran Wrap on top of your mash and don’t remove it until you clean your mash tun.
9. If you use pumps in your system, which most RIMS and HERMS systems will, double check all connections and fittings for leaks. Another good DIY project would be to figure out a way to pressurize your service lines and check for leaks with a spray bottle of soapy water.
By adding a drilled rubber “cork” that fits inside your discharge line, you should be able to insert the end of the CO2 blow gun in the “cork” and pressurize your lines while someone else sprays the connections and fittings with soapy water, looking for bubbles.
If you can purchase a dissolved oxygen meter, checking your pre-boiled strike water before and after circulating for a few minutes should indicate if there are any leaks.
You will notice the DO levels rise due to an ingress of oxygen into your system. DO meters are expensive. The cheapest models I found on Amazon were in the $155 range.
10. If using pumps to move your strike water and wort, keep the flow rate low, around 3-4 liters per minute (about 1 gpm). If you use propane burners to heat your mash (which most homebrewers will), you may need to bump up the flow rate to 6-8 liters/minute (1.5 to 2 gpm) to get even heating and to prevent scorching. Make sure the return line is below the top of the mash to prevent splashing and aerating the wort.
11. When lautering, a no-sparge process is best to minimize oxygen ingress in your wort. If you feel you must sparge, you will have to treat your sparge water just like your mash water. It must be pre-boiled and quickly cooled down to sparge temperature.
You must also add SMB at the rate of 10-15 mg/l. When sparging, you have to add the water gently to the top of the mash without splashing or aerating the mash in any way.
So, you may have to alter your sparge equipment if you use a sprinkling sparge arm or one with siphon sprayer. Try running your tubing and laying it directly on top of or below the surface of your mash.
12. Try adding a portion (30%) of your bittering hops as first wort hops (FWH) directly to the boil kettle during the lautering process, allowing them to steep while the sparge finishes. The German brewing forum guys have had great success with FWH in a LODO.
13. Use a 60 minute gentle boil, no more than a simmer. The evaporation rate should be in the 8-10% range. This evaporation rate should be sufficient to prevent DMS from entering your finished beer.
14. Chill the wort as rapidly as possible to fermentation temperaturewithout aerating it. This may be one of the most difficult alterations to the normal brew day that homebrewers will encounter when trying to brew with LODO.
For those using coolers who manually chill with an immersion chiller, some drastic alterations in the chilling process is in order. I normally have to stir the wort vigorously around the IC to get the wort cooled in a timely manner.
Any suggestions here would be welcomed by homebrewers who also use this method of chilling their wort. Most homebrewers would rather alter the mechanics rather than their equipment to save money.
15. You can allow the cold break material to enter the primary fermenter, but avoid letting the hot break or hop trub into the fermenter.
16. Consider the yeast as your best defense against oxidation. Getting the yeast into the fermenter as quickly as possible is a must. Mix the yeast in the wort well and add oxygen to the wort only after the yeast has been added, trying for about 8 ppm DO.
17. You want to transfer your wort to a secondary fermenting keg when it reaches 1°Plato (~4 gravity points) prior to full attenuation. You may have to do a forced fermentation test to determine what your final gravity should be with the yeast strain you have chosen. To learn how to do a forced fermentation test, click here.
18. For secondary fermentation in a keg, purge the receiving keg by filling the keg to the rim with sanitizer and then displace the sanitizer with CO2. You will have to cut the gas tube short to allow you to fill the keg as close to the rim as possible. You may also have to pressurize the keg with some CO2 to ensure that it seals.
19. After you finish racking to the keg, attach a spunding valve to the “beer out” valve on the keg. For instructions on how to fabricate a spunding valve, click here.
A spunding valve is basically a pressure gauge and a pressure relief valve connected by a wye to a liquid quick disconnect. It provides a way to naturally carbonate the beer and is a very important tool for controlling oxygen ingress for homebrewer.
By adding active yeast to the secondary fermenter, the final oxygen level after fermentation, conditioning, clearing and carbonation will be very close to zero.
20. Use the secondary fermenter as your serving keg. If you feel you carried over too much yeast and are worried about the off flavors of yeast autolysis, transfer to a keg purged in the same manner as you purged the original spunding vessel (secondary fermentation keg).
The main problem here is that you won’t have any active yeast available to consume the oxygen that gets into the beer. If you choose to bottle your beer, use a counter-pressure bottle filler. You still risk transferring the beer without active yeast but you will have much more control with the smaller volume.
The absolute best way to bottle beer after brewing with the low oxygen brewing method is to bottle with krausen. Click here to learn all about how this is done.
The Low Oxygen Brewing (LODO) method of brewing is relatively new to brewers and homebrewers in America. But, for a chance to completely transform the flavor of the malts in our beers, I think it is worth trying. A lot of experimentation still needs to be done.
REFERENCES: The article, “On Brewing Bavarian Helles: Adapting to Low Oxygen Brewing” by the Team at the German Brewing Forum www.germanbrewing.net, http://seanterrill.com/2015/06/25/build-a-better-spunding-valve/ , Accidentalis Brewing Blog article “Low Oxygen Brewing; Exploring LODO by Matt ?,