Sometimes the whys and what fors are forgotten after years of doing a certain technique that was added to the brewing process because the book or instructions said it is necessary. For years, my brewing process always included adding the copper wort chiller to the kettle with 10 minutes left in the boil for sanitization. Then after the boil is over, doing a whirlpool in the pot prior to running the cooling water through the coil.

The whole reason for this is to force all of the cold break (trub), hops, and hot break (trub) into the center of the pot, so the siphon has more room to operate when transferring the beer to the fermenter. The trub is made up of fatty acid and protein-tannin (polyphenols) compounds that can impact the beer's head retention and flavor. Now, having removed trub from my brews basically forever, I don’t even know what the flavor impact is anymore. Something to be brushed up on for sure. But the whirlpool does do the job, coupled with a screen on the siphon, to keep out the trub and hop particulate from the fermenting beer.

In any case, the trub does settle to the bottom as the kettle sits, and cooling is done. Be careful not to disturb the kettle prior to transferring so as to kick up the trub and get too much into your beer. I taste tons of homebrews, and something I need to identify is the flavors associated with trub. I love to taste great beer, and this is one of the steps necessary in making beer great.

There are those who have done experiments and the like to try and figure out whether trub truly is a detriment or not and whether it matters if it is removed. Trub is also said to help yeast get going, as it provides some necessary nutrients for the yeast. But it also provides necessary nutrients for bacteria and wild yeasts, which is probably the source of some off flavors as those baddies may do a little more fermenting than usual before the main yeast strain takes over and wins out.

There is a pretty good write up on trub the the 2nd Papazian book. It does mention that trub will hurt head retention and also cause some stale flavors. It also explains how to remove trub, including the whirlpool above.

The big breweries do not leave trub in the fermenters, so why should a homebrewer? Take the step to remove it, as the TGMBA believes it assists in making the best beer possible.