Low-Dissolved Oxygen Lagers
“I don’t know if it is a general problem to comprehend or follow instructions properly but hopefully others can break out of these habits and actually give [low dissolved oxygen brewing] a proper go!”
Such was one response (following an enumeration of my seven errors) to a blogpost detailing my first lackluster batch of low dissolved oxygen (LODO) helles. LODO brewing is an adaptation of the modern big-brewery process as developed by a group of homebrewers on the GermanBrewing.net forums. This collective has earned a reputation for both fanatical adherence to the writings of German brewing scientist Ludwig Narziss (author of Die Bierbrauerei) and an absolutist attitude that is at odds with the stereotypical laid-back homebrewer.
Their in-depth instructional PDF, On Brewing German Helles: Adapting to Low Oxygen Brewing,1 extols a wide variety of best practices related to hopping, mash acidification, fermentation, lagering, and packaging. However, it is their focus on keeping oxygen out of the mash and hot wort that has sparked considerable debate. This topic may sound like a reiteration of frequently downplayed concerns regarding hot-side aeration, but the LODO cadre is adamant that all experiments debunking it have been invalidated by the amount of oxygen dissolved in the experimental control inherent in the standard homebrewing process.
The LODO advocates go to excruciating lengths to limit hot-side dissolved oxygen to levels well below 1 PPM. At large breweries this is accomplished by nitrogen-flushing, steam-purging, and deaerating. At home, these steps are replaced by pre-boiling, underletting, and dosing sodium metabisulfite (SMB, a powerful antioxidant also used by homebrewers to convert chlorine to chloride). The claimed benefit is a fresher malt aroma in the wort. You must also eliminate copper and zinc, which catalyze oxidation. A low boil prevents heat stress from destroying delicate aromatics. On the cold-side, care is taken not to expel malt aromatics with an aggressive fermentation, nor destroy them with post-fermentation oxygen pickup.
Science
At 10 pages and 5,000 words I had hoped for more science to support the LODO claims. Their “proof” cites textbooks, but there aren’t any peer-reviewed papers to confirm their mechanics. Rather, the proponents appeal to the fact that there must be something to LODO if large breweries and equipment manufacturers are concerned, and to the obviousness of the flavor enhancement.
The authors cite George Fix’s Principles of Brewing Science (Brewers Publications, 1999) for this statement, “Oxygen can react with a great number of compounds in wort, including aromatic malt phenols. These compounds posses [sic] fresh, pleasant flavors and aromas on their own, but upon oxidation they quickly polymerize to form bitter tasting polyphenols and tannins.” While this is accurate to the cited work’s spirit, it muddles on the details. According to Fix, it is auto-oxidized melanoidins and fatty acids that steal electrons from phenols.
I was able to locate a few papers that have investigated the effect of sulfites on beer. A study by Andersen and Skibsted concluded that while sulfite addition to the mash slightly reduces oxidation analytically, the beer received lower sensory scores than untreated wort. These authors concluded that hexamethylenetetramine performed better from both a phenol-preservation and sensory perspective.2 Adding sulfites produces extraordinarily pale wort, likely a result of the inhibition of Maillard reactions.3 Might a small dose reduce the darkening of partial-boil extract beers? Sulfites have also been shown to prevent oxidation in fermented beer.4 Maybe it would extend the life of IPAs?
Experiment
Peer-reviewed publications are perfect for explaining phenomena and identifying areas for trial, but what really matters is how the beer tastes! I wanted to test if I, a nerdy, but not lager-obsessed homebrewer, could benefit from the LODO best practices. Complete success requires a DO meter, specialized equipment, and 10 or more trial batches to eliminate points of oxygen ingress and dial in the SMB dosage. However, even without perfect technique they claim incremental improvement is possible.
Several (friendlier) LODO devotees chimed in with suggestions for my second attempt. The most important improvement was to lower the SMB for a no-sparge mash; lack of clarity in the initial treatise caused me to double the intended rate. The characteristic fresh maltiness of LODO is said to be present in Budweiser and Guinness in addition to Weihenstephaner and Spaten, but I followed the suggested German recipe design (crystal/caramel malts especially benefit), yeast selection (White Labs WLP833 German Bock Lager), and fermentation (slowly lowering the temperature before fermentation finishes).
I collected 12 gallons (46 L) of pre-boil LODO festbier wort (which you can find a recipe for at the bottom of this page). I split the batch for reasons of timing, equipment size, and to avoid differences in the water profile (SMB adds sodium and sulfate). I treated half of the pre-boil wort gently: A soft boil then chilled through a CO2-purged stainless steel plate chiller. The other half I treated roughly: Splashing the wort for five minutes before a rolling boil, then a copper immersion chiller. I followed the suggested process for both halves after chilling including high yeast pitching rate, extra-cold fermentation, and spunding for carbonation (allowing the yeast to scavenge oxygen – see the March-April 2017 “Advanced Brewing” article for more on this).
I brought three counter-pressure-filled growlers of the ten week old beers to January’s DC Homebrewers club meeting where I conscripted 20 members for a blind triangle test. If a change in process can’t be identified in a side-by-side tasting, it suggests there isn’t a significant difference in the results. Only 7 of 20 tasters (P=0.52) correctly identified the unique LODO sample. That is consistent with 1-in-3 random chance. While several correct participants expressed confidence in their selection, so did several who were wrong. It would be unwise to trust the evaluations given the insignificant P-value, but of the five correct tasters with a preference only one selected the LODO sample.
I don’t want these results to suggest that there isn’t any value to LODO. I correctly identified the LODO sample in a blind test as being slightly maltier and fresher. What I’d love to see is a similar test from a brewer with a dialed in process!
Is LODO worth the effort?
Commercial brewing equipment designed to limit hot-side oxygen exposure may be a worthwhile investment for large breweries looking to preserve delicate malt aromatics. Homebrewing is a hobby, so many of us geek out about particular aspects. LODO isn’t going to be one of those for me, if for no other reason than the stress it adds to brew day. Homebrewing communities are usually open to the wide variety of paths to delicious beer. It bothers me when anyone says there is a single correct way, particularly when empirical evidence is lacking. For example, “Simply put, you cannot make a proper Helles without employing a low oxygen brewing process.”1
In 2014 Narziss (89 at the time) railed against the standardization and blandness of German beers at an Austrian Brewer’s Federation seminar. His list of complaints included boils that aren’t vigorous enough to drive off dimethyl sulfide (DMS), universal mash acidification, and high alpha acid hops and extracts. “The development over the last 50 years has been toward ever more similar, more and more neutral beers. Distinctive house flavors from esters, higher alcohols, resins have been reduced . . .”5
The process presented in On Brewing German Helles produces delicious lagers, but it is one method among many with that distinction!
References
1 http://www.germanbrewing.net/docs/Brewing-Bavarian-Helles.pdf
2 Andersen, M. L., & Skibsted, L. H. (2001). Modification of the levels of polyphenols in wort and beer by addition of hexamethylenetetramine or sulfite during mashing. Journal of Agricultural and Food Chemistry, 49, 5232–5237.
3 Wedzicha, B. L., & Kedward, C. (1995). Kinetics of the oligosaccharide-glycine-sulfite reaction – relationship to the browning of oligosaccharide mixtures. Food Chemistry, 54, 397–402.
4 Behavior of sulfites during fermentation and storage of beer. Journal of the American Society of Brewing Chemists, 54, 115–120. Kaneda, H., Takashio, M., Tomaki, T., & Osawa, T. (1997).
5 Translation: http://refreshingbeer.blogspot.com/2014/11/narziss-slams-state-of-german-brewing.html
LODO Festbier
(5 gallons/19 L, all-grain)
OG = 1.055 FG = 1.013
SRM = 4.9 IBU = 17.6 ABV = 5.5%
Ingredients
8.5 lbs. (3.85 kg) Weyermann Pilsner malt
2 lbs. (0.91 kg) Weyermann Vienna malt
10 oz. (0.28 kg) Weyermann Carahell® malt
3 oz. (85 g) Weyermann acidulated malt
3.5 Campden tablets (sodium metabisulfite)
4.6 AAU Hallertauer Mittelfrüh hops (60 min.) (2.3 oz./65 g at 2%
alpha acids)
1.7 AAU Hallertauer Mittelfrüh hops (10 min.) (0.8 oz./23 g at 2%
alpha acids)
White Labs WLP833 (German Bock Lager) yeast
Step by Step
Boil 9 gallons (34 L) of water for 5 minutes. Chill water to dough-in temperature with stainless-steel chiller. Dose with crushed Campden tablets and allow to sit 5 minutes. Add crushed grains to mash tun. Move water into the mash tun slowly through the spigot at the bottom. Target mash temperature is 152 °F (67 °C) for 30 minutes. Recirculate then run wort into kettle. Boil as gently as possible for 65 minutes, adding hops as noted in the ingredient list.
Do not add any yeast nutrient that contains copper or zinc. Chill with a stainless steel wort chiller to 42 °F (6 °C). Pitch 2.5 million cells per mL per °P. Aerate the wort.
Allow the fermentation to warm to 48 °F (9 °C) as it progresses until you reach 50% apparent attenuation, then chill 1 °F (0.5 °C) per day until you reach 43 °F (6 °C). Once the beer reaches 1.017–1.019, transfer to a well-purged keg and attach a spunding valve. Leave at 43 °F (6 °C) for a few weeks to ensure complete carbonation and final gravity are achieved. Lower the temperature close to freezing for four-to-eight weeks of lagering. I put mine on tap before that so I could taste it as it clarified.
