Author: Marshall Schott

With the growing popularity of homebrewing has come a ton of novel products to make the process both more convenient and less likely to lead to poor results. A perfect example of this can be seen in the sheer number of fermentation vessels available today as compared to just a decade ago, many or which are miniature versions of what professionals use on a much larger scale. When I got my start in 2003, I didn’t anyone who used anything other than a plastic bucket or glass carboy, in fact it wasn’t until 2012 that I made the move to PET carboys, which seemed ingenious to me at the time.

Nowadays, there are myriad styles of fermentation vessels ranging in size, material, and features. With numerous past xBmts producing results that suggest different types of fermentation vessels may in fact produce unique characteristics, I thought it would be good to compare the popular glass carboy to the relatively new Speidel HDPE tank.

| PURPOSE |

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

| METHODS |

I chose a really simple German Pilsner for this xBmt tod allow for any differences caused by the variable to shine.

Boondoggle

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 32.7 IBUs 4.5 SRM 1.049 1.010 5.1 % Actuals 1.049 1.01 5.1 % Fermentables Name Amount % Lager Malt (Muntons) 9.5 lbs 95 Vienna Malt 8 oz 5 Hops Name Amount Time Use Form Alpha % Magnum 11 g 60 min First Wort Pellet 11.2 Perle 11 g 25 min Boil Pellet 8 Hallertauer Mittelfrueh 80 g 10 min Boil Pellet 2.4 Yeast Name Lab Attenuation Temperature Super Special (Ü) Bootleg Biology 81% 46°F - 70°F Notes Water Profile: Ca 70 | Mg 1 | Na 10 | SO4 84 | Cl 62 Download Download this recipe's BeerXML file

I made a starter of a super secret Bootleg Biology yeast a couple days ahead of time.

The evening prior to brewing, I collected the full volume of filtered water and adjusted it to my desire profile.

I then weighed out and milled the grains.

My heat stick began heating the liquor a couple hours before I woke up, which meant it was nearly at strike temperature when I started brewing.

Using the no sparge method, I added the milled grains to the full volume of water.

After a couple minutes of stirring, I checked to make sure I’d hit my target mash temperature.

A pH reading 15 minutes into the mash showed it was right on target.

Once the 1 hour mash was complete, I began collecting the sweet wort.

The wort was transferred to my kettle and I began heating it up, measuring out the hop additions while I waited for it to reach a boil.

I boiled the wort for 60 minutes with hops added per the recipe.

At the end of the 60 minute boil, I quickly chilled the wort to a tad warmer than my groundwater temperature.

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

I proceeded split the wort evenly between a glass carboy and a plastic Speidel fermentation tank, racking 5.5 gallons/21 liters of chilled wort to each.

The filled fermentors were placed next to each other in a chamber controlled to my desired fermentation temperature.

It took 4 hours for both worts to stabilize at my desired fermentation temperature of 65°F/18°C, at which point I split the yeast evenly between the batches. I noticed airlock activity from both just a few hours later and fermentation progressed similarly in each. With signs of activity dwindling 4 days later, I raised the temperature to 72˚F/23˚C to encourage complete attenuation. After another 3 days, I took a hydrometer measurements showing FG had been reached.

I let them sit for 3 more days before I proceeding with cold crashing, fining with gelatin, and kegging.

The filled kegs were placed in my cold keezer where they were burst carbonated for 15 hours before I reduced the gas to serving pressure and allowed them to condition for another few days before collecting data.

| RESULTS |

A total of 20 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the beer fermented in the glass carboy and 2 samples of the beer fermented in the HDPE vessel in different colored opaque cups then asked to identify the sample that was unique. At this sample size, 11 tasters (p<0.05) would have had to select the unique sample in order to reach statistical significance, though only 6 (p=0.70) made the correct selection, suggesting participants were unable to reliably distinguish a German Pilsner fermented in a glass carboy from the same beer fermented in a plastic Speidel vessel.

My Impressions: These beers were exactly the same to my palate in every respect, there was nothing distinct about either, which explains my no-better-than-chance triangle test performance– in 8 attempts over 2 weeks, I was correct 3 times, and I’ll admit each one was a random guess. The beers were surprisingly tasty, I was glad to have 2 kegs around because it was an easy go-to lager when nothing else sounded appealing. Light, crisp, and thirst quenching with a really nice noble hop character that came off as more pungent than I expected based on the hop schedule. Definitely worthy of a re-brew!

| DISCUSSION |

This is the now the sixth xBmt we’ve completed that’s been focused on fermentation vessel and the third in which tasters were unable to distinguish a difference between the beers. I’d hypothesized that one potential explanation for prior significant xBmt results on this topic was headspace and geometry differences between vessels. However, seeing as though glass carboys, Speidel tanks, and Ss Brew Buckets aren’t necessarily identical in size and shape, it would appear my hypothesis was likely wrong. Another thought I had was that the material the vessel is made of somehow impacts a beer’s characteristics, perhaps leeching certain compounds into the beer that subtly effect its flavor. While I can’t be certain this isn’t happening, the evidence at this point seems to suggest something else may be at play.

There are a couple things I can think of that all of the fermentation vessels used in the non-significant vessel comparison xBmts have in common– they are highly impermeable to oxygen and they were all relatively new at time the xBmts were completed. Anyone who has ever stored a sour beer in a plastic bucket or PET carboy knows that they let in more oxygen than other types of vessels based on how quickly a pellicle forms, and given the significant results of our recent cold-side oxidation xBmt, it’s possible this ingress has a perceptible impact. It also seems like the stuff that stains well used plastic fermentation vessels could also impact beer flavor, carrying over whispers of flavor from past batches that ultimately combine to have an impact on the overall character of beer.

I’ve personally taken a strong liking to the Ss Brewtech Brew Buckets for their durability and overall ease of use. Being stainless, they’re essentially impermeable to oxygen and don’t stain, making them safe from either of the aforementioned issues. I also really like the Speidel plastic tank for its very thick HDPE wall and screw on lid that will also keep oxygen out, though I am curious about how the plastic will hold up over multiple batches. I have a buddy who has been using Speidel tanks for awhile and they’re definitely a different color than my new-ish one. I suppose a good future xBmt will involve comparing a new plastic fermentor to one that’s been well used.

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

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