Author: Jake Huolihan

Debated ad nauseam by professional and homebrewers alike, hot side aeration (HSA) occurs when wort is treated in a manner that introduces what many believe to be excessive amounts of oxygen in the period between mashing and knockout. It seems a growing number of brewers have accepted HSA as a non-issue, though some continue to view it as a brewing bogeyman that leads to rapid staling and, of primary concern on the commercial scale, poor shelf stability.

We’ve performed a couple xBmts on HSA, the first comparing beers when they were fresh and the second after a period of aging, with neither returning significant results, meaning participants could not reliably distinguish low HSA samples from high HSA versions of the same beer. While it’d be easy to rely on these findings and the anecdotal reports of others to bolster one’s perspective of HSA as myth, a passionate group of German beer loving homebrewers recently introduced an idea that calls this into question.

In a document released in April 2016 called Brewing Bavarian Helles: Adapting To Low Oxygen Brewing, members of the German Brewing Forum laid out a method for producing Helles and other traditional lagers that have “it,” the seemingly ineffable characteristics of genuine Bavarian beer that a few have described as “fresh malt flavor.” The authors of the paper assert this character can only be achieved on the homebrew scale by utilizing a very specific set of processes intended to significantly reduce oxidation not just from the mash onward, but throughout the entire process– conditioning grain, pre-boiling strike water, underletting, and spunding, to name a few. Perhaps most curious of these methods involves using a “modest dose” of sodium metabisulfite (SMB), a compound whose proven antioxidant properties have made it a popular preservative in the food and beverage industry. However, as Dr. Charlie Bamforth once pointed out in an interview, commercial brewers have generally refrained from using SMB likely due to laws requiring disclosure of content over thresholds as low as 10 parts per million (ppm). Moreover, the authors of the paper suggest certain large commercial breweries are capable of brewing in a low oxygen environment due purely to larger mash volumes, which is impossible at the homebrew scale without the use of SMB.

As someone with a strong adoration for German beer who feels I haven’t been able to replicate the quality of what I drank while visiting the region, I was very intrigued by these ideas, to say the least. With heaps of hope, a small dose of skepticism, and a bit of an investment in the gear required to properly brew a so-called LODO (LOw Dissolved Oxygen) batch, I designed an xBmt to help me better understand the impact oxidation throughout the brewing process has on beer.

Note: Given the common usage of the term LODO, we opted to use it throughout this article when referring to the low oxygen brewing method laid out by the German Brewing Forum and espoused by the Low Oxygen Brewing website.

| PURPOSE |

To evaluate the differences between a beer brewed using methods to significantly reduce oxygen throughout the brewing process (LODO) and the same beer brewed without such methods.

| METHODS |

I began messing around with LODO brewing immediately after reading the aforementioned paper, before I had all of the necessary gear. I soon learned that, according to some advocates of the method, even the slightest deviation from protocol, such as using a copper immersion chiller instead of a stainless one, would likely mitigate the desired “it” character. It wasn’t until my setup was completely LODO-fied that I performed this xBmt, as my goal was to test the method as precisely as possible and see how it compared to a batch treated in a less oxygen restricted manner. Munich Helles is the style most associated with LODO, but I went with a simple Kölsch for this xBmt after a strong advocate of the method confirmed low oxygen brewing can positively impact any style; I did use a charge of Carahell in the recipe due to claims it lends a noticeably unique flavor to the beer when mashed in a low oxygen environment.

SuffoKÖLSCHian

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 19.8 IBUs 3.5 SRM 1.044 1.009 4.6 % Actuals 1.044 1.014 3.9 % Fermentables Name Amount % Weyermann Pilsner Malt 9 lbs 91.72 Caramel/Crystal Malt - 10L 6 oz 3.82 Weyermann Vienna 4 oz 2.55 Acid Malt 3 oz 1.91 Hops Name Amount Time Use Form Alpha % Hallertau Magnum 8 g 60 min Boil Pellet 12.5 Hallertauer Mittelfrueh 30 g 30 min Boil Pellet 2.4 Yeast Name Lab Attenuation Temperature Kolsch Yeast (2565) Wyeast Labs 75% 56°F - 64°F Notes Water Profiles:



Standard: Ca 82 | Mg 0 | Na 21 | SO4 101 | Cl 95 | HCO3 16

LODO: Ca 76 | Mg 0 | Na 21 | SO4 102 | Cl 93 | HCO3 16

I prepared a large starter of Wyeast 2565 German Kölsch yeast a couple days prior to brewing to ensure an adequate pitch rate.

I began filtering my brewing water the night before brewing.

It was at this point I carefully measured out all of the brewing salts. As indicated in the original document, “a 100 mg/l dose of SMB will add 24 ppm sodium to your water, and 76 ppm of sulfur compounds (sulfur dioxide, sulfite, and bisulfite).” Since xBmt results have demonstrated minerals have a noticeable impact on beer, and the point of this xBmt was to isolate the effects of low oxygen, I used the Bru’n Water Spreadsheet to determine amounts of other minerals to use so that both batches would finish with a similar water profile; ultimately, the non-LODO batch received slightly more gypsum and calcium chloride than the LODO batch.

My first order of business the following morning was pre-boiling the strike water for the LODO batch in order to off-gas any dissolved oxygen. The standard batch was simply heated to the strike temperature recommended by BeerSmith.

A measurement of the LODO strike water after only 10 minutes of boiling revealed a very low level of remaining dissolved oxygen (DO).

I let the LODO water continue to boil while I prepared the grains. With two sets of the same amount of grains already weighed out, I ran one through my mill as I normally do before proceeding with preparing the malt slated for the LODO mash. As recommended by Kunze, I used 1.5% water by weight to condition the grains before milling, a step the authors of the referenced document say “will keep the husk intact and reduce the number of lipoxygenase and peroxidase enzymes into the mash, which would otherwise accelerate the oxidation of malt lipids and phenols.”

I started the mash for the standard batch before the LODO batch by transferring the slightly overheated strike water to my MLT for a brief period of pre-heating before incorporating the grist. The LODO batch required a bit more work…

After chilling the boiled water with a stainless steel immersion chiller to the target strike temperature, I added 55 mg/l of SMB to the water and let it rest to scavenge any remaining oxygen. A DO measurement revealed 0.2 ppm, which when adjusted for altitude (Denver is high) meant there was basically no oxygen present; in contrast, the adjusted DO level of the standard strike water was 5.3 ppm. Next, I very gently transferred the water from the kettle through the valve on the bottom of my MLT that already held the milled conditioned grain in a process known as underletting.

I utilized the no sparge method for both batches, meaning each was mashed with the full volume of brewing liquor, and I placed a mash cap (an old kettle lid that conveniently fit my MLT) on top of the LODO mash to further inhibit oxygen ingress.

Temperature measurements from both mashes showed a slight variation, which I chalked up to the different methods used for mashing in.

With claims that oxidation can quickly have a visible impact on wort, I stole small samples of wort throughout the mash rest to observe any differences in appearance, an initial sample just minutes into each mash confirming said claims.

I took more samples 30 minutes into each mash and, to my eyes, they still looked quite different.

Separate samples, the one from the LODO mash sealed to reduce contact with oxygen, were chilled before I took DO measurements.

At 60 minutes into each mash, before collecting the sweet wort, I pulled more samples for comparison, again sealing the LODO sample and chilling both before taking DO readings.

I lautered each batch similarly by allowing the wort to flow from the MLT valves to the valves on my kettles, as bottom-filling is another way to reduce oxygen ingress. I also made sure no bubbles were in the hose and no splashing occurred during the transfer.

Both worts were boiled very gently for 60 minutes, the standard batch only to avoid potentially large differences in evaporation due to boil vigor.

Once the boils were complete, I used my copper immersion chiller to quickly chill the standard batch to my groundwater temperature while I used a stainless steel IC to chill the LODO wort without any agitation, which required much more time.

The chilled worts were gently racked to sanitized corny kegs, the one receiving the LODO wort having first been purged with CO2 (sanitizer pushed out with gas), before being purged again and placed in a cool chamber to finish chilling to my desired 58°F/14°C fermentation temperature. Hydrometer measurements showed the normal batch achieved the expected 1.044 OG while the LODO wort clocked in at a much lower 1.035 OG (50% efficiency), which is exactly as I’d experienced in multiple prior brews using this method.

After sharing an image of both worts with the other contributors, we began to speculate that perhaps the color difference was a function of the standard wort simply having a higher concentration of sugar. To test this out, I diluted the standard wort sample with water until it reached the same 1.035 SG as the LODO wort then compared them again with validating results.

A couple hours later, both batches sitting at target fermentation temperature, I equally split the yeast starter, pitched, hit both with 90 seconds of pure oxygen, then attached blowoff tubes.

I noticed a bit of bubbling in the blowoff vessel a few hours later indicating fermentation had indeed begun. After 3 days of activity, I took hydrometer measurements indicating the LODO beer was within a few points of reaching FG, which meant it was time to rack to serving kegs. I sanitized two kegs, again filling the one intended for the LODO beer with sanitizer and pushing it out with CO2 to purge, then filled them using a pressure transfer process.

Spunding valves were placed on the gas-out posts of each keg, the one on the LODO beer set to the recommended 8 bar while the standard beer was left under no pressure. They sat for another 5 days at 62°F/17°C before I began to slowly reduce the temperature in my fridge to 32°F/0°C. I let the beers lager at this temperature for 4 weeks before I took final hydrometer measurements.

The kegs of naturally carbonated beer were moved into my keezer and put on just enough gas to allow for serving. After letting the beers settle for a few days, I pulled initial samples that looked great!

| RESULTS |

A huge thanks to Colorado Grist Busters Homebrew Club and CO-Brew Homebrew Supply in Denver, CO for allowing me to collect data during a meeting!

A panel of 38 people with varying levels of experience participated in this xBmt. Each taster, blind to the variable being investigated, was served 1 sample of the beer brewed with standard oxygen levels and 2 samples of the beer made using LODO methods in different colored opaque cups then instructed to select the unique sample. While 19 participants would have had to identify the unique sample in order to achieve statistical significance, a total of 25 (p<0.05; p=0.00004) made the accurate selection, indicating tasters in this xBmt were indeed capable of reliably distinguishing a LODO Kölsch from the same beer made with higher amounts of oxygen.

The 25 participants who made the correct selection in the triangle test were instructed to compare only the 2 different beers, still blind to the variable in question, and asked about their preference. In all, 15 tasters reported preferring the beer under normal conditions, 5 said they liked the LODO beer more, 3 people had no preference despite noticing a difference, and 2 tasters felt there was no difference between the beers.

My Impressions: In samples tasted prior to the lagering phase, I perceived a rather strong sulfur component in the LODO beer that I figured would dissipate over time. Given my excitement about this variable, I attempted more triangle tests with these beers than I have on any other xBmt, and sure enough, I was consistently able distinguish the LODO beer from the one made using standard practices. To me, the LODO beer maintained a slight aroma of hydrogen sulfide (H2S) that made it fairly easy to identify, even after an additional few weeks in my cold keezer. The beer from the standard batch had what I perceived as a honey note, perhaps from the Carahell, that I found immensely pleasing and more preferable than the LODO version.

Side exBEERiment: Proponents of the LODO method have expressed concerns about the perilous nature of both packaging and shipping, namely that it can rapidly erase the benefits brewers work so hard to create. To test this out, I sent 3 inconspicuously marked bottles to Marshall, 2 the same and 1 different. He and 2 friends who were unaware of the variable all failed their triangle test attempts. Marshall attempted 4 more times with the remaining beers and was correct just once, though he admitted he resorted to guessing.

| DISCUSSION |

On an objective level, the results of this xBmt provide evidence that the use of SMB is effective at reducing oxygen levels throughout the brewing process, which isn’t nearly as exciting to read as it is to observe, as it can be easily explained by chemistry. And, as the authors of the referenced document often point out, the information they’re sharing isn’t necessarily new at all, in fact they extensively credit German brewing scientists Ludwig Narziss and Wolfgang Kunze as advocating the merits of brewing in low oxygen environments long ago. Of course, their focus was on large-scale commercial beer production, and given their stature in the brewing world, I’m compelled to take them at their word. However, as scientists, I also trust they’d understand the interest in testing things out for oneself, particularly given the smaller homebrew scale we operate on that requires the use of interesting techniques, namely the use of SMB for oxygen scavenging.

Prior to collecting data for this xBmt, I contacted Dr. Charlie Bamforth, the Anheuser-Busch Endowed Professor of Malting and Brewing Sciences in the Food Science and Technology department at UC Davis, to seek his thoughts on using SMB in the production of beer. His response was straightforward, “Sulfites in the mash are to be avoided, yeast will reduce it to sulfide and you will end up with an egg-y aroma in your beer.” Perhaps this explains the H2S I’ve perceived in the various LODO beers I’ve brewed.

Indeed, the beer brewed using LODO methods was different enough from the batch made with standard oxygen levels that a significant portion of tasters could tell them apart. Curiously, a whopping 60% of those who could distinguish the beers endorsed the standard one as their preferred, whereas only 20% liked the LODO beer more, drastically contrasting the 90% preference rate for the LODO beer in another experiment. Why so disparate? And what about the growing number of reports that LODO has helped brewers achieve the Bavarian “it” character they so long for and couldn’t produce prior to employing techniques to reduce oxygen throughout the brewing process?

It’s possible the results of this xBmt are a function of the OG and subsequent ABV differences between the standard and LODO beers, though if that were the case, I would have expected Marshall and his friends, at least one of them, to be able to confidently identify the odd-beer-out in the samples I sent. But that’s not what happened, none of them could tell the beers apart and they all described them as tasting very similar, supporting the idea shipping may remove whatever it is the LODO method imparts. This makes me wonder how German breweries who ship beers to the US that I believe have “it” do it, as well as how homebrewers who say LODO helps them do well in competitions keep the character present.

I’ve thought about this a lot lately and came up with a few other potential explanations for the findings from this xBmt:

Bad Methodology

LODO brewing is an involved process, far more so than most homebrewing approaches, requiring myriad steps that if missed can ruin the whole shebang. Take a look at any forum or blog post from someone whose attempt at LODO brewing resulted in less than stellar results and you’ll almost certainly find someone pointing out how the methodology is to blame. As confident as I am in my methods due to following the paper as closely as I could, consulting with LODO adherents throughout the process, and brewing multiple batches using LODO methods prior to this xBmt, sure, it’s possible I screwed something up and that the LODO beer would have been more preferred if I hadn’t. I’m also a process nut, so if this is the case, I have to wonder about the success rate of most other homebrewers.

“It” Doesn’t Exist

Frankly, I’m a believer in “it” and feel there is a unique character to many Bavarian lagers that I’d love to be able to reproduce at home but haven’t been able to. Still, it’s one possibility, extreme as it may be.

“It” Exists But Isn’t Preferred

The only problem I have with this is that I adore all of the German beers LODO advocates claim have “it,” yet between the beers in this xBmt I preferred the one brewed using standard methods. Maybe my LODO Kölsch had too much “it” and there’s a level at which it becomes overbearing, sort of like the way many view Crystal malts?

“It” Exists But It’s Not The Same “It” LODO Produces

This notion stems from my love of German beers that I think have an elusive desirable character coupled with my preference for the non-LODO beer in this xBmt. It’s plausible there is something special to German beers and even that it’s due to low oxygen brewing, but that as a function of scale, we’re simply unable to replicate it. Moreover, it’s reasonable to assume that relying on SMB for oxygen scavenging impacts beer character beyond what one might expect in an oxygen and sulfite free environment.

Whatever it is, I really don’t know, and honestly, I really don’t care. A growing number of homebrewers who have adopted the LODO method swear it allows them to make better beer, which is fantastic! There’s no reason they should stop doing what works for them, in the same way people who are happy with the beer they make using standard homebrewing approaches need not change.

Cheers to those who have invested the time to explore these methods in such depth and share their findings with the homebrewing community, their passion for producing delicious beer is admirable. In no way am I willing to accept oxygen doesn’t have some deleterious impact on beer, though neither will I accept it does to the extent believed by some. Combining the results of this xBmt with my prior experiences using this method, the reports from others who have tried it out, and what I’ve gleaned from brewing professionals, I’ll be hanging up my LODO gloves for the time being. Not because it doesn’t work, just that it’s not for me.

If you have experience using low oxygen methods or have thoughts about this xBmt, please don’t hesitate to share in the comments section below!

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