Author: Marshall Schott

Back in June 2014, I performed The Great Trub exBEERiment, which suggested fermenting beer with higher amounts of kettle trub led to a clearer beer with a crisper taste. Data collection for this xBmt was somewhat clunky, as I’d yet to fully hone my method. While I did perform a triangle test, it wasn’t the focus, which led some to question the validity of the results, understandably so.

Since that article was published, I’ve heard from many (many) people who either had been fermenting with tons of kettle trub or who started doing so after reading the article, all who claimed to have a similar results. Prior to the xBmt, I was one of those brewers who would allow the trub to settle out before racking, though I’ve since stopped worrying near as much and I don’t believe it’s had a negative impact on the beer I make. Regardless, I’d been wanting to get back to this one using the slightly more controlled data collection method I’ve since adopted. And besides, a single point of data does not a principle make.

| PURPOSE |

To compare the impact different amounts of kettle trub in the fermentor have on 2 beers made from the same wort and fermented with the same yeast.

| METHOD |

I had recently decided I wanted to submit a Vienna Lager in the NHC and only had about a month until the beers were due, hence my choice of style. I was also interested to see how kettle trub might have a different impact using my yeast of choice for this beer, WLP 810 San Francisco Lager Yeast.

NHC Vienna Lager Batch Size Boil Time IBU SRM OG Est. FG ABV 11 gal 75 min 22.1 11.4 1.053 SG 1.013 SG 5.2% Fermentables

Name Amount % Gambrinus Vienna Malt 9 lbs 48 Franco-Belges Belgian Pils Malt 6 lbs 32 Gambrinus Munich 10 Malt 3 lbs 16 Gambrinus Honey Malt 8 oz 2.7 Briess Midnight Wheat 4 oz 1.3

Hops Name Amt/IBU Time Use Form Alpha % Magnum ~20.3 IBU 60 min Boil Pellet 12.2 Spalt 40 g/1.9 IBU 10 min Boil Pellet 3.1

Yeast Name Lab Attenuation Ferm Temp WLP810 San Francisco Lager Yeast White Labs 65-70% 58°F

A few days prior to brewing, I made a large enough starter to propagate the predicted amount of yeast for two 5 gallon batches of 1.053 OG wort. This would later be evenly split and decanted before being pitched.

The brew day started out as usual, early in the morning, and I nailed my mash temps. After an hourlong mash, the wort was collected, the boil commenced, hops were added, then the wort was chilled to 58˚F, my target fermentation temperature. I should add that 8 grams of Irish moss was added at 5 minutes to flameout.

In order to maximize the amount of trub transferred to the high-trub fermentor, I tilted the kettle forward and used a spoon to gently coax as much out as possible. Once that carboy was full, I tilted the kettle backward and let the trub settle for 15 minutes before opening the valve and filling the no-trub fermentor.

I can’t seem to find the picture, but suffice it to say the difference between the carboys was stark. Both were placed in the fermentation chamber and pitched with equal amounts of WLP810. This is where the observable differences began. The high-trub beer showed active signs of fermentation hours before the no-trub and appeared to ferment with more vigor. The no-trub beer eventually appeared to be catching up and by a week post-pitch, after the temp had been ramped to 68˚F, the krausen had pretty much fallen on both beers and airlock activity was at a standstill.

I took an intial hydrometer reading a few days later and immediately noticed some differences.

While neither beer had attenuated to expected FG, I was pretty surprised to discover the no-trub beer was barely below 1.030 SG. Also, the high-trub beer was already looking a bit clearer by comparison.

In order to encourage a bit more attenuation, I bumped the temp on my Black Box regulator to 72˚F and let both beers sit a few more days. The high-trub batch maintained its appearance for the most part, while the no-trub batch began developing interesting looking bubbles on the surface of the beer.

After a few days at this warmer temp, I took a second hydrometer reading.

It’s interesting to note the expected FG for this beer was 1.013, which the high-trub beer had surpassed and the no-trub beer was still above. To be sure, I let the beers sit another few days before taking third and fourth hydrometer samples 2 days apart, the readings were consistent at this point.

After being cold crashed and fined with gelatin, I kegged the beers then placed them in my keezer to carbonate.

The difference between each batch in terms of overall trub amount was pretty drastic.

The beers were left to condition/lager and carbonate for about week before being presented to participants for evaluation, at which point they were about as clear as any commercially available example (condensation be damned).

| RESULTS |

Besides generally tightening things up in terms of data collection compared to the first kettle trub xBmt, another important-to-note difference is that the samples for this one were served to each taster in opaque cups, meaning they would be forced to rely on characteristics other than appearance to make their determination. In all, 18 people participated in this xBmt, requiring a minimum of 10 (p<0.05) to choose the different beer to reach statistical significance. Each person was blindly served 3 samples, 2 of which were the no-trub beer. A total of 8 tasters correctly identified the high-trub beer as being different from the others, while the other 10 participants chose either of the similar samples. Yet again, these results suggest there is no statistically significant perceptible difference between beers fermented with very high and very low amounts of kettle trub.

But what about the people who did taste a difference?

Given the fact we were only 2 tasters short of reaching significance, I thought it might be interesting to share the perspectives of those who were correct when asked to compare only the 2 different beers. Please, when reading this next part, do so with the understanding that these are meaningless findings from a purely statistical perspective. Sure, there’s a chance the correct tasters just have better palates, but the dickhead in me is compelled to think they’re likely just better guessers.

Of the 8 participants who accurately selected the high-trub beers as being the different sample…

…all but 1 perceived the aroma to be somewhat similar, that single straggler believing they were not at all similar; 5 preferred the aroma of the no-trub sample and 3 preferred the aroma of the high-trub sample.

…everyone felt the flavor was somewhat similar with, again, 5 preferring no-trub and 3 preferring high-trub.

…5 tasters perceived the mouthfeel as being somewhat similar, 2 as exactly the same, and 1 person though they were not at all similar; of those who thought there was a difference, 2 preferred the mouthfeel of the no-trub beer while 4 preferred the high-trub beer.

My Impressions: As usual, I began drinking these beers a few days prior to the start of data collection and from the very first comparative sip, I knew which one I’d be entering into the National Homebrew Competition. Whether due to bias (probably) or not, I much preferred the beer fermented with a ton of kettle trub, not just because it had what I perceived to be as a crisper, cleaner flavor, but for some reason the no-trub beer had what I can only describe as a subtle plastic aroma and flavor, something I’ve only ever experienced one other time when I significantly under-pitched harvested yeast into a 1.055 wort. Was this the effects of yeast stress? Is there something about kettle trub that ameliorates the these types of off-flavors? Am I just making this up?

| DISCUSSION |

The lack of statistical significance in this xBmt supports previous findings, as well as the anecdotal reports of myriad homebrewers, that higher amounts of kettle trub making it to the fermentor do not necessarily impact beer in a detrimental way, as many were taught to believe. Since the appearance of each beer was not evaluated, in addition to the fact both batches were fined with gelatin, a comment on the clarifying function of kettle trub cannot be made. Moreover, the easily observable differences in fermentation vigor, overall attenuation, and time to reach FG between each batch suggests something about kettle trub contributes positively to fermentation activity in general. While I’m uncomfortable and far too stupid to make any claims of certainly as to why this is the case, I’ve heard speculation that it has something to do with increased lipids… I won’t pretend to know more than I do. In the end, these results have only served to solidify my belief that worrying about racking only the clearest wort to the fermentor is unfounded and a waste of energy.

Since revealing the results of the first trub xBmt, many folks have proposed the idea that perhaps increased kettle trub during fermentation has some negative impact on shelf life. I have to admit, shelf-life isn’t something I’ve ever been terribly concerned with when it comes to homebrewing, as most of my batches stick around for maybe a month. Still, for those who sit on their beer longer, this is certainly a major limitation to my research. For what it’s worth, I’m currently sipping a pint of the high-trub Vienna lager, brewed nearly 6 weeks ago, and it is delicious! I still experience that whisper of plastic in the no-trub beer, though really, it’s quite tasty as well. I ended up entering the high-trub version in NHC, here’s to hoping it does as well as I hope!

Are you a filterer or a toss-it-all-in type? Regardless, please don’t hesitate to share your experience in the comments section below. Cheers!

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