Probably time we did a comprehensive post on this one as it's a good question.
Reliable Sources of Information
The first thing, like anything in home brewing, is not to rely on a few posts from home brewers for the following reasons...
1. Homebrewers have very little ability to experiment when it comes to subtleties in brewing practices. Several side by sides, sometimes many, need to be conducted to make any sort of conclusions on a brewing practice. Despite this, it is not uncommon to see homebrewers jumping to incorrect conclusions such as, "I did this on one brewday, therefore it will work on my next brewday."
2. Even if something does make a positive difference on one beer style, it does not mean it will be a positive in other beer styles.
3. It is not uncommon for any individual brewer to be unable to detect certain off-flavours. For example, I may be able to pick up astringency where you can't and you may be able to pick up diacetyl when I can't. So it is quite possible that a brewer may be totally unaware that they even have a problem. Lucky for them!
What We Do Know - Trub 'Positive' - More vigorous fermentation.
The addition of trub in the fermentor can lead to a more vigorous fermentation due to the trub acting as CO2 nucleation sites which means basically that the suspended cell concentration is higher. (See
here.)
Generally, the fermentation will start sooner and finish earlier.
What We Do Know - Trub 'Negative' - Off flavours
Here is a collection of sources on the effects of trub in fermentation.
Lager brewers believe cold break removal aids in colloidal stability in the beer, circumvents the formation of sulfury flavors, and removes harsh bitter fractions derived from hops. De Clerck suggests that clearer worts lead to beers that clarify better (7). It is reported that if significant amounts of trub are carried over into the ferment, the yeast will produce an excess of fusel alcohols. It has also been reported that suspended solids can lead to adverse effects on foam and flavor stability.
from The Brewer's Handbook by Ted Goldammer
Effective removal of hot trub before fermentation is critical because the trub can smear the yeast's cell walls, impeding the transport of substances in and out of the cell, which can lead to head retention problems, poor flavor stability, and harsh bitterness in the palate of the beer.
Hot Trub: Formation and Removal by Ron Barchet
...with more delicate beers there seems to be more possibility of having unacceptable sulphury aroma and taste.
Malting And Brewing Science by Hough, Stevens and Young.
Finding the Balance
Like a lot of things in brewing, there is not enough information to have the perfect answer for every beer style. I think my favourite quote, not sure if it is scientifically correct or not, was from a pro brewer, "Yeast like trub like we like candy but it's not necessarily good for them."
Before we get to a final bit of advice, we also need to consider what one means by trub. If I have used a hopsock and dump all my kettle contents into the fermentor, that is entirely different from someone who doesn't use a hopsock and dumps all their trub into the fermentor.
That is a big difference.
Here is what I think is sensible practice...
1. Do everything you can to reduce hop trub. Using your BIAB bag as a hop sock works really well.
2. Don't try and get every last drop of liquid from your kettle. Plan and allow for some wastage.
3. Don't go to clumsy or difficult lengths to avoid some cloudy wort going into your fermentor. For example, filtering through cloths etc is likely to cause you a whole lot of other potential problems.
Finally for no-chillers. Do number 1 above for sure but be less worried about everything else going into the cube. This will settle out.
The above is my best interpretation of what is out there but I really do think it's one of these areas we will probably never be able to get enough quality information on.
PP
P.S. I hope that helps because it took 1.75 hours of my Sunday morning to write

. How that time just vanishes is another thing I think I'll never work out

.
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