Author: Marshall Schott

Back in December 2016, we published an xBmt article on post-fermentation oxidation with results showing participants could not reliably distinguish between a Pale Ale kegged using either high or low oxidation methods. These findings surprised many, present company included, and naturally led to speculation as to why the beers weren’t more disparate in character. While some claimed the damage had already been done to both beers since low oxygen (LODO) methods weren’t used to brew them, the fact oxidation is a commonly cited issue in beer that isn’t brewed using said methods suggested something else may be at play.

The most common critiques of the aforementioned xBmt were that the 4 weeks I allowed the beers to age wasn’t enough and the temperature at which they were stored was too cool. The argument was that oxidation is a function of both time and temperature, namely that beer left in a warm environment over a long period of time runs a higher risk of developing the stale characteristics of oxidized beer. Could it be that the results would have been different had I stored the beers warmer and longer? Curious like a cat, I devised a plan to test it out for myself!

| PURPOSE |

To evaluate the differences between a beer packaged under conditions promoting high oxidation and the same beer packaged under relatively low oxidation conditions after both were aged at room temperature for 100 days.

| METHODS |

Given reports of oxidation having a strong impact on hop character, I brewed a relatively hoppy Pale Ale for this xBmt.

2 Birds, 1 Stone, & 4 Months Pale Ale

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 11 gal 60 min 37.0 IBUs 5.3 SRM 1.057 1.012 5.9 % Actuals 1.057 1.012 5.9 % Fermentables Name Amount % ESB Pale Malt (Gambrinus) 15.25 lbs 68.54 Pilsner (Weyermann) 7 lbs 31.46 Hops Name Amount Time Use Form Alpha % Centennial 30 g 60 min Boil Pellet 7.3 Centennial 20 g 30 min Boil Pellet 7.3 Centennial 60 g 15 min Boil Pellet 7.3 Centennial 60 g 5 min Boil Pellet 7.3 Centennial 104 g 3 days Dry Hop Pellet 7.3 Yeast Name Lab Attenuation Temperature Safale American (US-05) DCL/Fermentis 77% 59°F - 75°F Notes Water Profile: Ca 87 | Mg 1 | Na 10 | SO4 125 | Cl 62 | HCO3 200

The night before brewing, I collected the water for this full volume no sparge batch, adjusting it with minerals and acid to my target profile, then weighed out and milled the grain.

I hit the flame under my kettle first thing the next morning, adding the slightly overheated liquor to my mash tun for a 5 minute preheat, then mashed in with some help from my adorable assistant, Hazel.

With the grain fully incorporated into the brewing liquor, I measured the temperature and found I was right about where I wanted to be.

About 15 minutes into the mash, I pulled a small sample for a mash pH reading, it was precisely where Bru’n Water predicted.

After a 60 minute rest, I collected the full volume of sweet wort in my trusty graduated bucket then transferred it to the kettle.

When the wort reached a rolling boil, I set a timer for 60 minutes and made hop additions according to the recipe.

At the conclusion of the boil, I quickly chilled the wort to a few degrees warmer than my groundwater temperature, which was a bit warmer than my desired fermentation temperature.

A refractometer measurement showed I’d hit my target OG.

The chilled wort was evenly split between two fermentors and placed in my cool chamber to finish chilling to my target fermentation temperature of 66°F/19°F.

I returned about 4 hours later to pitch vitality starters I’d made earlier with Safale US-05 dry yeast. The following morning, about 12 hours later, I noticed airlock activity indicating active fermentation in both fermentors. I allowed the beers to ferment for 3 days before bumping the temperature up to 72°F/22°C. With signs of active fermentation absent after another 3 days, 6 days total, I took preliminary hydrometer measurements and added the dry hop charge.

After 3 days on the dry hops, I took a second hydrometer measurement that matched the first, confirming fermentation was indeed complete.

The beers were cold crashed overnight then fined with gelatin before I proceeded to the packaging phase where the variable was introduced. For the normal batch, I used my typical method of transferring the beer from the fermentor to a sealed and non-purged keg through the liquid-out post, a depressor on the gas post to allow air out as the beer fills the keg.

In order to maximize oxidation in the experimental batch, I cut a small length of vinyl tubing, attached one end to the spout on my Brew Bucket, dangled the other end in the unsealed keg, opened the valve, and let the beer splash into the keg.

The filled kegs were placed in my keezer where they underwent a brief period of burst carbonation before I reduced the gas to serving pressure. I let them sit for 4 full weeks before collecting data for the initial xBmt, at which point both were clear and carbonated.

The evening that xBmt article was published, inspired by some comments it received, I removed the approximately half-full kegs from my keezer and placed them in my spare shower where the temperature was a consistent 68-72°F/20-22°C. I let them age in this warm environment for precisely 100 days (12/19/16 to 3/29/17) before moving them back to the keezer. After another 10 days in the keezer to allow for settling of anything that got jostled into solution, the beers were clear and ready to present to tasters, both looking nearly identical.

| RESULTS |

A panel of 20 people with varying levels of experience participated in this xBmt. Each taster, blind to the variable being investigated, was served 1 sample of the low oxidation beer and 2 samples of the high oxidation beer in different colored opaque cups then instructed to select the unique sample. While a total of 11 correct selections (p<0.05) would have been required to achieve statistical significance, only 9 tasters (p=0.19) accurately identified the unique sample, suggesting participants in this xBmt were unable to reliably distinguish a Pale Ale packaged under presumably high oxidation conditions from the same beer kegged using a method to reduce oxidation after an extended period of aging.

Given the fact significance was not reached, the subsequent preference data collected is essentially meaningless, but for the sake of fellow curious brewers, I figured I’d share it anyway. The 9 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, 4 tasters reported preferring the beer kegged using low oxidation methods, 3 said they liked the high oxidation beer more, 1 person had no preference despite noticing a difference, and a single taster felt there was no difference between the beers.

My Impressions: My first attempt at a triangle test on these beers came after witnessing 3 people in a row make the correct selection, which obviously meant more to me at the time than the fact the next 5 people got it wrong. Either way, I was curious to see how different the beers were and had intentionally held off on sampling so as to save the surprise. Not only did the beers taste exactly the same as each other to my palate, but based on my sensory recollection, they didn’t really taste any different than when I sampled them in the first go-round of this xBmt. Neither had what I’d describe as quintessential oxidation character, at least the wet cardboard or sherry characters often discussed, but rather both were pretty much how I remember them being a few months earlier. Over a total of 6 attempts, I chose the unique sample twice, exactly what you’d expect from my random guessing.

| DISCUSSION |

Warm temperature and age– two things I trust most brewers agree are to be avoided for the majority of beer styles. Despite believing 4 weeks was enough time for any negative effects of kegging with high oxidation to show in the first iteration of this xBmt, I have to admit I was downright convinced the similarities between the beers would diminish after an additional 100 days of warm storage, the high oxidation sample tasting of stale grain and wet cardboard. But that’s not how things panned out. In addition to the beers tasting largely similar to each other, not a single taster, in follow-up conversations, described either in a way that would indicate oxidation as being an issue. The mind boggling thing is that at least one of the beers was arguably highly oxidized– just watch the video, if you can bear to get through it. Moreover, oxidation has been noted to have a darkening effect on beer color, yet both looked the same and, to my eyes, neither looked terribly different than the image from the first xBmt.

I don’t really know how to convey with words how surprised I am with these results. Oxidation is real and I’ve zero doubt it occurred on some level, but the fact it wasn’t drastic enough to make these beers taste different from each other or different from the time data was first collected has me scratching my head. Perhaps its true what some claim that oxidation occurs much earlier in the process and that the “damage” is done long before packaging, though if this is the case, where the hell were the expected oxidized flavors? While I’ve absolutely no plans to embrace such lazy kegging practices, I can’t help but question about the impact oxygen during packaging really has on beer. Would I recommend people intentionally engage in splashy racking? Of course not, that’s stupid, but perhaps an accidental bump of the tubing when kegging or racking to a bottling bucket isn’t worth fretting over all that much.

If you have thoughts on this xBmt, please feel free to share in the comments section below!

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