Author: Jake Huolihan

Considered a spoilage organism by many, Brettanomyces (Brett) is a genus of yeast known for being highly attenuative and producing unique characteristics not found in beer fermented with Saccharomyces alone. While historically avoided by all but perhaps a few Belgian and English brewers, the growth in popularity of wild and sour ales has done wonders for stripping Brett of its bad reputation. Well regarded breweries such as Crooked Stave, Russian River, and The Rare Barrel rely on Brett, often in conjunction with other yeast and bacteria, to produce award winning beers.

Given the rich history of wild and sour ale, it should be no surprise that strong opinions exist regarding best practices when it comes to beers in which Brett is used. Perhaps as a function of its strong attenuation abilities, Brett beers are often served with a fairly high amount of carbonation, and the method used to create said carbonation is viewed by many as being a key contributor to the quality of the finished product. Those favoring natural carbonation speak about its numerous benefits including finer bubbles, creamier head, and even the development of desirable flavor characteristics due to pressures put on the yeast during the conditioning phase. Alternatively, these beers can be force carbonated just like any other beer, with many claiming it has no perceptible impact while simplifying the process.

One of my favorite commercial beers is Orval, a Trappist ale that’s hit with Brett following primary fermentation with a Belgian yeast strain. It’s also naturally carbonated in the bottle, a feature believed by many to positively influence the overall drinking experience. With a couple past xBmts suggesting no difference between natural and force carbonation, I was curious to see how things would play out with Brett in the mix and decided to put it to the test!

| PURPOSE |

To evaluate the differences between force carbonation and bottle conditioning in beers inoculated with Brettanomyces following primary fermentation with a Saccharomyces strain.

| METHODS |

Purportedly modeled after English pale ales, Orval is known for a fresh hop clean character when fresh which evolves in the bottle due to the presence of brett. I whipped up a simple English style ale and got to brewing.

Favre

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 53.6 IBUs 6.5 SRM 1.053 1.005 6.4 % Actuals 1.053 1.008 5.9 % Fermentables Name Amount % Pilsen (Dingemans) 4.125 lbs 40 Special Pale (Cargill) 1.5 lbs 14.55 Vienna Malt (Weyermann) 1.25 lbs 12.12 Carahell (Weyermann) 1.125 lbs 10.91 Crystal, Dark (Simpsons) 3 oz 1.82 Sugar, Table (Sucrose) 2.125 lbs 20.61 Hops Name Amount Time Use Form Alpha % Perle 30 g 60 min Boil Pellet 8 Saaz 30 g 60 min Boil Pellet 1 Perle 25 g 30 min Boil Pellet 8 Saaz 15 g 30 min Boil Pellet 1 Perle 30 g 0 min Boil Pellet 8 Yeast Name Lab Attenuation Temperature Precious (B53) Imperial Yeast 76% 65°F - 73°F Suburban Brett (W15) Imperial Yeast 78% 64°F - 74°F Notes Water Profile: Ca 44 | Mg 0 | Na 8 | SO4 65 | Cl 33 Download Download this recipe's BeerXML file

After gathering my grains the night before brewing, I prepared the water by adjusting it to my desired profile then scheduled my heat stick to turn on a few hours before I planned to start the next day.

I started off my brew day by milling the grains.

With the water properly heated, I incorporated the grist then checked the mash temperature.

The mash was left to rest for 60 minutes during which I stirred every 15 minutes with my large whisk.

With the mash step complete, I collected the sweet wort in a kettle.

The wort was then boiled for 60 minutes, during which the hops and sugar were added at the times stated in the recipe.

Once the boil was complete, I quickly chilled the wort.

A refractometer reading showed the wort had achieved my target OG.

Equal amounts of wort were then transferred to a pair of identical fermentation vessels.

After connecting the filled fermentors to my glycol chiller set to maintain both at 66°F/19°C, I pitched a pouch of Imperial Yeast B53 Precious into each one.

Both beers were vigorously fermenting 6 hours later and were left alone for 7 days before I took hydrometer measurements confirming they had reached the same SG.

The beers were then racked to separate kegs.

At this point, I pitched a pouch of Imperial Yeast W15 Suburban Brett into each beer.

While the beer that would be force carbonated had a standard blowoff tube connected to the gas post, I attached a spunding valve to the natural carbonation batch and set it to a PSI that would produce the desired volume of CO2 based on ambient temperature. After a month of conditioning at approximately 65°F/18°C, I took a second set of hydrometer measurements that showed the beers finished at the same SG.

After a couple weeks in my cool keezer, both beers shared the same level of carbonation and clarity, making them ready to serve to unsuspecting participants.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the force carbonated beer and 1 sample of the naturally carbonated beer in different colored opaque cups then asked to identify the unique sample. While 12 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 10 (p=0.12) did, indicating participants in this xBmt were unable to reliably distinguish beers secondarily fermented with Brettanomyces that were either force carbonated or naturally carbonated.

My Impressions: Out of the 5 triangle tests I attempted, I guessed correctly exactly one time. To me, both beers were more similar than different, which was great seeing as this was one of the best beers I think I’ve ever made, truly a joy to drink!



| DISCUSSION |

Viewed by many as being one of the biggest inconveniences in brewing, others hold bottle conditioning in high regard, particularly when it comes to funkier styles fermented with wild yeast. While there’s no arguing the fact that CO2 is CO2, the idea that certain conditions under which carbonation occurs can have some sort of qualitative impact seems, at the very least, plausible. However, corroborating past results, tasters in this xBmt were unable to tell apart Brett beers that were either force carbonated or naturally carbonating, suggesting carbonation method may not have the impact some believe.

From one perspective, these results may feel a bit dismal, a knock to the romanticism that accompanies engaging in the tediously traditional task of bottle conditioning. However, there is a bright side– natural carbonation is an easy way to save a few bucks on CO2! Sure, certain approaches may require a bit more time, for example those who skip spunding and rely on dosing the beer with priming sugar, but the benefit is using significantly less CO2. Spunding valves are great because they allow for carbonation via the gas produced by fermentation, so not as much waiting, plus they look pretty cool too.

These results only serve to further strengthen my belief that the way I carbonate my beers likely isn’t having much of an impact. Perhaps there are certain conditions we’ve yet to test that will suggest otherwise, but as for now, I’m comfortable accepting the either approach works just fine. As someone who regularly uses both force and natural carbonation methods, this is a good thing.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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