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Author: Marshall Schott

Recent xBmt results seem to support the notion that different types of fermentation vessels have an impact on the character of the beer fermented in them. I did not expect this to be the case, to say the least, as I’ve always viewed fermentor type as being rather inconsequential.

Maybe it’s not?

After releasing the findings from the last xBmt on this topic showing tasters were able to reliably distinguish a beer fermented in a glass carboy from one fermented in a PET carboy, I received a barrage of requests to do some comparisons with other types of fermentors. I was honestly shocked with how interested people were in this variable, particularly given the less than enthusiastic response I got from my friends who participated in the previous triangle tests. Of course, this was before the results were analyzed and released. I’m now very curious whether different fermentation vessel types produce a measurable qualitative impact on the beer we make, as well as if the differences we’ve seen thus far will be consistent between multple xBmts.

Known for being impermeable to oxygen and easy to keep sanitized, stainless steel is the most common material used by modern professional brewers to ferment beer in. In the recent past, homebrew options consisted of pricey conicals that were essentially scaled down versions of what’s found in larger brewing operations. However, less cumbersome stainless fermentors have recently become available that are similar in form and function to typical homebrew buckets. Having recently acquired such a product, the Ss Brewtech Brewmaster Brew Bucket, it seemed only prudent to pit it against another fermentor extolled by many for it’s oxygen impermeability, the popular glass carboy.

| PURPOSE |

To evaluate the differences between beers produced using the same process where one was fermented in a stainless vessel and the other in a glass carboy.

| METHODS |

The beer I chose to brew for this xBmt is a rye IPA designed in collaboration with Love 2 Brew that is now available in kit form!

Including hefty doses of rye malt and El Dorado hops, Collabrüation Rye IPA is a medium bodied beer that’s uniquely candy-like without being sweet or cloying, a fun diversion from the typical citrus-bomb IPAs out there. Included with the kits were packs of WLP090 San Diego Super Yeast, which I propagated in starters a couple days prior to brewing.

The evening before brewing, I collected my full volume of brewing liquor, which I passed through a carbon filter, and added the necessary minerals and acid to bring it to my preferred IPA profile.

Next, the pre-measured grains from the two Collbrüation Rye IPA kits were milled together by my talented friend, Matt Humann.

I started the following morning off by hitting the flame under my strike water.

While the water was heating, Josh Evans, a local homebrewer I’d met online, stopped by with some delicious Berliner Weisse he’d made. Perfect for a warm morning brew session! Once the water was about 7°F/4°C warmer than the recommended strike temperature, I transferred it to my MLT then let it preheat a bit before Josh assisted me with mashing in.

After ensuring the grist was well incorporated with the liquor, I measured the temperature and found we’d pretty much nailed the target.

The mash was left to rest for an hour, receiving a brief stir every 20 minutes, then I performed a standard batch sparge to collect the proper volume of sweet wort, which was then put on the flame and quickly brought to a boil.

Kettle hops were added over the course of a 60 minute boil, after which I quickly chilled the wort to 170°F/77°C and tossed in the large hop stand charge. Twenty minutes later, with everything else all cleaned up, I finished chilling the batch. Given my warm groundwater temps this time of year, I was only able to get the wort down to 82°F/28°C, which is 16°F/9°C warmer than my preferred fermentation temperature, but it only took 9 minutes.

I filled both the stainless Brew Bucket and the glass carboy with equal amounts of warm-ish wort, stirring gently throughout to ensure equal distribution of kettle trub, then I placed them in my cool chamber to finish chilling. About 6 hours later, both batches having reached my target fermentation temperature, I divided the large starter equally between the two fermentors. As I’ve come to expect from WLP090 San Diego Super Yeast, the beers were fermenting happily the following evening.

Minimal though it may be, one downside to fermenting in stainless is that it makes observing fermentation characteristics impossible, which I think can be interesting for some variables. This one, not so much. After 3 days at 66°F/19°C, I bumped my regulator up to 72°F/22°C, allowing the temperature of the beers to rise naturally in order to encourage complete attenuation and clean-up of any undesirable fermentation byproducts. I dry hopped 2 days later and let them mingle with the beer for 5 days before I pulled a hydrometer sample confirming I’d reached the target FG.

The beers were another couple of days then cold crashed, fined with gelatin, then transferred to kegs.

The full kegs were placed in my keezer and hit with 45 psi of CO2 for 18 hours before I reduced to serving pressure. By the following weekend, both beers seemed to share identical levels of carbonation, though curiously, the one fermented in stainless was noticeably clearer.

| RESULTS |

A total of 19 people participated in this xBmt, each blindly served 1 sample of the beer fermented in a stainless steel Brew Bucket and 2 samples of the beer fermented in a glass carboy. While 11 tasters (p<0.05) would have had to accurately identified the odd-beer-out at this sample size, 5 (p=0.81) were able to do so, suggesting participants in this xBmt were not reliably able to distinguish a beer fermented in a stainless steel vessel from the same beer fermented in a glass carboy.

| DISCUSSION |

Perhaps the most common theory regarding the significant findings from the first two fermentation vessel xBmts had to do with dimensional and volumetric differences between the fermentor types. On a commercial scale, I can sort of wrap my mind around how this might have an impact, but it seemed rather far-fetched to think such relatively small differences as an inch in diameter or a half-gallon more head space would matter all that much. Considering the Ss Brewtech Brew Bucket is different in terms of both dimension and volume than a glass carboy, yet tasters weren’t able to reliably distinguish between beers fermented in either, I’m left skeptical this is really the culprit.

Then what is it?

While impossible to know for sure based off of these few bits of data, it’s curious to me that the only time tasters haven’t been able to perceive a difference between beers fermented in different types of vessels has been when the material the fermentors are made of are know for disallowing any oxygen into the beer. Prior to buying my first PET carboy years ago, I anxiously scoured the web for information about oxygen issues with PET. The general consensus, based on experience and research, was that buckets allowed the most oxygen in and PET allowed much less. Assuming this is accurate and oxygen is the culprit, the findings from all 3 fermentation vessel xBmts actually make sense.

What’s your experience fermenting in different types of vessels? Please share in the comments section below!

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