exBEERiment | Fermentation Vessel: HDPE Bucket vs. PET ...
exBEERiment | Fermentation Vessel: HDPE Bucket vs. PET ...
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Author: Andy Carter
Every homebrewer has to start somewhere, and for most it usually involves picking up a beginner’s kit that comes with a small kettle, spoon, hydrometer, some hop bags, and of course, a food-grade plastic fermentation bucket. Cheap, effective, and easy to clean, plastic buckets are made of high-density polyethylene (HDPE) and remain the fermenter of choice for some, particularly those who prefer the simpler side of brewing.
However, despite their general convenience, many brewers end up relying on other types of fermenters due to certain issues with plastic buckets, namely oxygen permeability and how easily they scratch. While glass carboys were once the most common alternative, less expensive plastic carboys have grown in popularity over the years. Made of polyethylene terephthalate (PET), these newer vessels are lighter in weight than glass while offering reduced oxygen permeability than plastic buckets. Moreover, PET is a bit harder than HDPE and thus more resistant to scratches that can harbor beer spoilage microbes.
Plastic buckets are certainly the cheapest fermentation vessel option, though PET carboys have become the mainstay in my fermenter corral due primarily to concerns of post-fermentation oxygen exposure—that large diameter opening is a nice place for air to come in when taking hydrometer samples and racking to kegs. With one past xBmt suggesting tasters could tell apart an IPA fermented in a plastic bucket from one fermented in a PET carboy, I was curious to test it out again for myself.
| PURPOSE |
To evaluate the differences between a Pale Ale fermented in a HDPE bucket and one fermented in a PET carboy.
| METHODS |
Given concerns of oxygen permeability, I opted to brew a Pale Ale for this xBmt, the recipe of which was lightly inspired by Sierra Nevada Pale Ale.
Beginner’s Luck
Recipe Details
Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 37.3 IBUs 9.9 SRM 1.055 1.012 5.6 % Actuals 1.055 1.005 6.6 %Fermentables
Name Amount % Pale Malt (2 Row) US 10 lbs 90.91 Caramel/Crystal Malt - 80L 1 lbs 9.09Hops
Name Amount Time Use Form Alpha % Sterling 20 g 60 min Boil Pellet 8.6 Sterling 20 g 20 min Boil Pellet 8.6 Sterling 43 g 5 min Boil Pellet 8.6Notes
Water Profile: Ca 43 | Mg 5 | Na 8 | SO4 65 | Cl 44Download
Download this recipe's BeerXML fileI started my brew day by adding identical volumes of RO water to separate BrewZilla units, adjusting each to my desired mineral profile, then setting the controller to heat it up.
While waiting on the water to warm, I weighed out and milled two identical sets of the grain.
Once the water for each batch was properly heated, I incorporated the grains then checked to make sure they hit my target mash temperature of 150°F/66°C.
While the mashes were resting, I prepared the kettle hop additions.
Once each 60 minute mash was complete, I removed the grains and sparged to collect the same pre-boil volume.
Following each 60 minute boil, I ran the wort through my chiller while being pumped to either a plastic bucket or PET carboy.
Refractometer readings showed both worts hit the same target OG.
I placed the filled fermenters next to each other in my chamber and let them finish chilling to my desired fermentation temperature of 66°F/19°C for a few hours before returning to pitch a single pouch of Imperial Yeast A07 Flagship into each.
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After 5 days of active fermentation, I raised the temperature to 70°F/21°C and let them sit for another week before taking hydrometer measurements confirming both reached the same FG.
With the beers done fermenting, I racked them to sanitized kegs, doing my best to keep things as equal as possible.
The filled kegs were placed in my keezer and left on gas for 3 weeks before I began evaluating them.
| RESULTS |
Due to social distancing practices as a result of the COVID-19 pandemic, data for this xBmt was unable to be collected in our typical manner. As such, temporary adaptations were made involving the author completing multiple semi-blind triangle tests in as unbiased a way as possible.
Utilizing 4 opaque cups of the same color where 2 were inconspicuously marked, one set was filled with the beer fermented in a HDPE bucket while the other set was filled with the beer fermented in a PET carboy. For each triangle test, 3 of the 4 cups were indiscriminately selected, thus randomizing which beer was the unique sample for each trial. Following each attempt, I noted whether I was correct in identifying the unique sample. Out of the 10 semi-blind triangle tests I completed, I needed to identify the unique sample at least 7 times (p<0.05) in order to reach statistical significance, though I did so just 5 times (p=0.21), indicating my inability to reliably distinguish a Pale Ale fermented in a plastic bucket from one fermented in a PET carboy.
When packaging these beers, I could have sworn the one fermented in a bucket had stronger aromas of yeast and fruity esters, whereas the batch fermented in a PET carboy had more spice and citrus. However, once kegged and conditioned, any differences I thought I perceived had disappeared, the beers were identical in every way. I felt the citrusy bouquet from the Sterling hops paired well with the richer specialty malt character in this beer, which had a solid bitterness balanced by a grainy sweetness. A bit more complex than the typical Pale Ale, but still clean and very drinkable!
| DISCUSSION |
There are number of factors that go into deciding what type of fermentation vessel best suites a brewer’s needs, though for most beginners, the decision is made for them—a plastic bucket. As one becomes more obsessed with crafting the finest beer possible, they’ll eventually hear of the ills of fermenting in such vessels and feel compelled to consider alternatives, a popular choice being PET carboys, which purportedly reduce the risks of oxidation and contamination. My inability to reliably distinguish a Pale Ale fermented in a plastic bucket from one fermented in a PET carboy suggests fermenter type had little if any perceptible impact.
Seeing as these findings contradict those from a prior xBmt where tasters could tell apart beers fermented in either type of vessel, it’s worth considering possible explanations. While I’m inclined to point to the fact the initial xBmt had a sample size of just 10 participants, all of them were blind to the variable, whereas I as the single participant was completely aware of everything about these beers. Presuming the difference perceived in the first xBmt was real, I wonder if it wasn’t in some way a function of flavor carryover from the many batches of beer that had previously been fermented in the bucket. It’s also possible any differences between the beers were below my personal flavor threshold and, if served to a group of participants, a significant number would have performed better on the triangle test.
I adopted PET carboys as my fermenter of choice for various reasons, and while the results of this xBmt won’t convince me to give them up, they did increase my confidence in using HDPE vessels for fermentation. As someone who occasionally ages beer the primary fermenter, I maintain a level of concern about the oxygen ingress that can occur when using buckets for such a purpose and view that as a good variable to explore in the future.
If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!
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