I took a couple bottles from the Bavarian Hefeweisen I brewed for the newest BBR/BYO collaborative experiment to the MUGZ meeting this afternoon. This experiment was to determine the effect of leaving trub (that gunk that collects at the bottom of your kettle after cool-down) in the finished beer. Personally, I tend to throw most of the trub into the fermentor, although I couldn’t tell you why.
To perform this experiment, I brewed a new version of my Hefehosen. After cooldown, I racked the top half of the kettle into one 3 gallon fermentor for the “clean”, non-trub half. The rest I dumped directly into an identical 3 gallon fermentor for the “dirty”, trub-ified half. I aerated each half with my aquarium pump for 15 minutes and then pitched half a vial of WLP380 into each fermentor. This didn’t look like much yeast at all, so I found an ancient (best before 9/2010) satchel of Danstar Munich yeast and added 6 grams of it to each fermentor. I then placed both fermentors side-by-side on a shelf in my cellar, to ferment at 64F.
I took a picture of their status every day. In each picture, the “clean” half is on the right, and the “dirty” half is on the left. Not that I needed to tell you that… I mean, look at them:

Day 5. It's hard to tell from the photo, but the dirty half is done fermenting but the clean half is still doing a little work.
Visually, there was a big difference. The dirty half started later, but finished sooner, which makes me think that the trub is beneficial to a healthy, quick fermentation. Aromatically, the clean half was much more intense during fermentation. Whenever I would remove its tinfoil hat the smell would punch me in the face – loads of phenols and some sulfur action going on. Later on in fermenation that dropped off and was replaced with a pleasant banana character. Meanwhile, the dirty half was much less intense, but more muddied. It was hard to pick out what exactly I was smelling, although later on I did get a lot of clove.
I bottled after 10 days in the fermentor, and had my wife give me a blind triangle test 6 days after that. After watching the fermentation and smelling them, I didn’t find this to be a challenge. I easily picked out which was which. The dirty half had a very defined clove character in the nose and mouth and visually was less cloudy. The clean half had banana characteristics in the nose and mouth and was pretty cloudy. I’m thinking the dirty half’s healthier fermentation was to blame here. I have heard that if you want a clovey weizen, pitch a lot of yeast and if you want a banana-y weizen, pitch less. Although I pitched the same yeast in both fermentors, the trub provided a more ideal environment for the yeast and therefore simulated a higher pitching rate.
When I took the samples to MUGZ, I didn’t tell anyone what sample was what. I just had the mysterious labels of A and B. A being the dirty (trub-ified) half and B being the clean (no-trub) half. I asked the testers to fill out little slips of paper saying which they thought was the trub sample and which they preferred. Here are the results:
13 people thought the dirty sample (A) had the trub removed.
3 people thought the clean sample (B) had the trub removed.
5 people said they couldn’t tell.
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6 people said they preferred the dirty sample (A)
13 people said they preferred the clean sample (B)
2 people said they didn’t have a preference
What can we get from this? For one, if the 21 testers are a good representation of the general public, then what most people think of as a “dirty” beer is wrong. On the same token, 13 people preferred the clean beer while less than half preferred the dirty beer. 5 out of 21 people couldn’t tell the difference. Thanks to all the testers by the way!
So will this change the way I brew? Actually I think it will. Sure, the fermentation took longer in the clean half, but people obviously preferred it over a beer where you just throw all the trub in. But then again, a Hefe is all about the yeast – strain and pitching rate. I’d love to see the results from a beer where the yeast doesn’t take center stage (maybe a Stout or a Pilsner?).












