Sunday, March 29, 2015

Don't be afraid of the Trub!

In a lot of home brewing books, and perhaps in the minds of many home brewers, is the advice that you should separate your beer from the trub during fermentation.  (Trub, also known as lees, refers to the sediment that appears at the bottom of the fermenter.) The prevailing wisdom is that trub will cause the finished beer to be more cloudy, have "off flavors", and generally turn out worse than a beer moved off the trub into a secondary fermenter.

The folks who make the Grainfather did an experiment in February to see if the prevailing wisdom is correct.  Would a beer kept on the trub throughout its fermentation taste worse, look more cloudy, have poorer head retention, etc., than a beer removed from the trub?

For the experiment, they brewed an American Pale Ale (APA).  Half of the batch was fermented with as little sediment as possible.  The other half was given as much sediment as possible.  If the trub made any difference in the beer, this experiment should make that difference very obvious.  Their recipe for the APA was:

  • 4.5 kg pale malt
  • 1 g Simcoe hops at 60 minutes
  • 150g of Simcoe hops at whirlpool
  • Mangrove Jacks Burton Union yeast

After brewing, half the batch was poured through a sanitized sieve to strain all possible particulate matter out of it.  The other half got all the trub when it went into the fermenter.

The beers fermented identically, starting with a gravity of 1.044 and ending with 1.005.

After 7 days, the fermenters were moved to a refrigerator to cold crash them before bottling.  After chilling, another gravity measurement was taken to ensure that gravity had remained the same.  It had.  A quick taste test showed that the sample from the trub-filled fermenter actually was more bitter than the one from the trub-free fermenter.

They got 14 bottles from the trub-filled fermenter and 18 from the trub-free one.  So if you want better yields, avoiding trub is a good idea.

A blind taste test was then performed of the two beers after bottle conditioning.  Tasters were asked to judge the clarity, aroma, head retention, and comment on any off flavors they detected.  The results were surprising.

The beer brewed with the trub was judged to be clearer by all four tasters.  It was also judged to have the better aroma.  Tasters were split 50/50 on head retention, but all agreed that it was similar for both beers.  But home brewers probably care most about flavor...  how did that turn out?

All four tasters preferred the beer fermented with the trub.  They said its flavors were clearer and more defined than the beer fermented without trub.

When asked to guess which beer had been fermented with trub, all four were wrong.

The conclusion arrived at by the brewer were that a high proportion of trub can be beneficial.  It can improve clarity, aroma, and flavor.  The downside to leaving the trub in is that it did reduce their yield by 22%.  Perhaps it would be good to reduce trub but not eliminate it when homebrewing.

Whether you choose to leave the trub in your beer during fermentation or not, the good news is that you shouldn't have to worry if you can't get it all removed.  Your beer may actually benefit from a little trub making it into the fermenter.

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