The Trub Experiment

Gravity samples on trub beers

Whilst reading a Reddit AMA with Peter Wolfe, an Anheuser-Busch brewing scientist, I was drawn to a comment thread about the effects of trub on fermenting beer. Many people were pointing to an experiment conducted by brulosopher in which he deliberately includes trub in his fermenter to measure the results;

He states, ‘there is no appreciable difference between homebrewed beers when the trub is or is not transferred.’

I began to question why I had always been so careful to pour the beer off of the trub when transferring it to my fermenter. What effect would including this sediment have on the overall clarity and taste of the beer and does it have any effect on fermentation? I decided I needed to conduct my own experiment.

METHOD

Brew an American Pale Ale and split the batch, being careful to avoid transferring sediment into one fermenter and deliberately including as much as possible in the second. This is to test what effect trub vs no trub has on the end quality of the beer.

RECIPE

4.5kg pale malt

1g Simcoe @ 60 minutes

150g Simcoe @ Whirlpool

Yeast:  Mangrove Jacks Burton Union

fly sparging

Fly sparging the grains

Sparging

I mashed at 67°C for 60 minutes with a fly sparge

The brew itself went without a hitch and after chilling my wort down to fermenting temperatures I poured half of the batch through a sanitised sieve to strain out as much hop debris and break material as possible before stirring all the trub into the remaining wort and pouring this all into a separate fermenter.

Preparing to filter trub

Wort chilling before being transferred

The gravities for the beers are shown below;

Trub No Trub
Day 1 1.044 1.044
Day 4 1.020 1.021
Day 5 1.005 1.005
Day 6 1.005 1.005
Day 7 1.005 1.005
Day 8 1.005 1.005

 

On Day 7 the fermenters were moved to the brew fridge to cold crash ready for bottling on Day 8.

After chilling at 12°C for a day I took another gravity sample to check everything had stayed the same. After tasting the samples there were already some noticeable differences –the sample from the trub filled fermenter was much more bitter than the none trub sample.

Gravity samples on trub beers

Trub on the left, no trub on the right

After bottling there was some pretty interesting looking trub left in the fermenters;

No trub sediment

No trub

 

Trub leftover

Trub

Overall I managed to get 14 bottles from the trub filled fermenter and 18 from the no trub fermenter.

TASTING

I carried out blind tastings and asked 4 colleagues to advise preferences on clarity, aroma and head retention then to state any detectable off flavours and if they could spot which beer had trub in the fermenter.

The beers were poured into 4 lots of separate glasses (so every taster had a glass of each).

Chilled beer clarity test

Clarity differences (No trub on the left)

Clarity

Mike Paul JK Bernie
With Trub Yes Yes Yes Yes
Without Trub

 

Aroma

Mike Paul JK Bernie
With Trub Yes Yes Yes Yes
Without Trub

 

Head Retention

Mike Paul JK Bernie
With Trub Yes Yes
Without Trub  Yes  Yes

All tasters agreed that the head retention was similar on both beers

Chilled beers close up

Off Flavours

Of the two beers, three of the four tasters said that the flavours in the beer with no trub were not as ‘clear’ or ‘defined’ as those in the beer that had been fermented with trub.

Can you guess which beer had trub in the fermenter?

Mike Paul JK Bernie
With Trub
Without Trub  Wrong  Wrong  Wrong  Wrong

 

All four tasters got this question wrong

RESULTS

No Trub

This was the second favourite of the tasters in terms of clarity, aroma or flavour – tasting similar to the trub version but the flavours were less clear and defined. Head retention was good but all tasters incorrectly identified this as being the trub filled beer as it was the significantly hazier of the two.

Trub clarity test

Trub

The hands down winner, this was everyone’s favourite for clarity, aroma and flavour. Good carbonation, it poured pale and clear with a good head. Some particles were still floating in the beer but the lack of haze led everyone to think this was the no trub version of the beer.

No trub clarity test

 

CONCLUSIONS

From this experiment it would seem;

  • A high proportion of trub can be beneficial, helping with clarity, aroma and overall flavour.
  • Trub may actually help sharpen beer flavours
  • In a blind taste test none of our tasters could correctly identify the beer from the trub filled fermenter.

Obviously this experiment has taken things to extremes and we aren’t suggesting that any homebrewer would deliberately mix all the trub in their kettle into their wort and add this to the fermenter but the experiment does seem to demonstrate that there is no need to worry if some debris does get into your fermenter and in fact, some trub can be beneficial; aiding in clarity, aroma and flavour as well as providing nutrients for yeast. The downside is that you are likely to reduce beer yield from the fermenter (we got 22% less).

How careful are you when transferring wort of the trub and what is your experience with its effects on your beer? Let us know in the comments.

4 Comments

  • Reply December 19, 2014

    Pete

    Great experiment! I have seen experienced brewers on BIABrewer say that they don’t worry about transferring trub, and that it is a natural yeast nutrient.
    I generally transfer quite a lot of trub, but then worry that it it causing poor clarity -thanks for demonstrating that it probably is not! Plus, the 22% volume loss at bottling is likely offset by the extra ~22% that you transfer from kettle to fermenter.

    • Reply December 22, 2014

      David Bawden

      Hi Pete,

      It would be interesting to repeat the experiment with a higher ABV beer and see if the trub really does act as a nutrient by monitoring the yeast performance – this time around the fermentation’s were almost identical. It does seem that overall transferring trub shouldn’t have a negative effect on your end beer clarity which is good!

  • Reply December 20, 2014

    David

    In a way it’s a shame the clarity gave the tasters a misleading steer. Quite possible this subconsciously influenced their assessment of the other characteristics.

    If repeating this experiment, maybe the aroma and flavour assessments could be conducted with the beers in opaque drinking vessels, or with the tasters blindfolded.

    • Reply December 22, 2014

      David Bawden

      Hi David,

      We still have bottles of both beers left which we’re hoping to test in a month’s time just to see how they have changed and I think as you suggest we should do that as a blind tasting because it would be interesting to know how much the difference in clarity affected the results!

Leave a Reply