Transferring Hop Trub to the Fermenter

Right or wrong, I long ago viewed the production of beer to include many steps where things are modified, separated and moved to the next step of the operation. The malting process, for example, includes barley cleaning before steeping, and includes the removal of rootlets following malt kilning. Go to a hop farm during harvest and you will see equipment that separates leaves and bines from hop cones prior to kilning. Most brewing water is treated using a variety of techniques along the path to make the water clear, clean and suitable for use in brewing. And even the yeast we use for pitching is often concentrated before use by decanting off the beer resulting from the propagation step. In a nutshell, we seize the opportunity to remove something that is not needed or wanted in the finished beer when the opportunity presents itself.

Now that I have given some background on my way of thinking, it should come as no surprise that I am not a huge fan of the method you describe for no other reason than because trub and hop solids are easy to remove following the boil. But the contrarian will argue that the overall batch yield will improve if this technique is tempered, for example, in the manner you describe. I have no objection on the basis of yield, but I am concerned about the downstream consequences of this method.

My immediate concern is the quality of the yeast crop. If the plan is to crop yeast from this fermentation and pitch it into a subsequent batch you will have to contend with trub and hop solids in the cropped yeast. This concern is more than simply being picky; trub is known to “foul” the surface of the yeast cell wall and the health of cropped yeast is influenced by what settles with it to the bottom of the fermenter.

And my other concern is how the hop solids will affect flavor. One thing that I find pretty useful when contemplating “flavor what-ifs” is to take a sample of the substance in question and taste it. If it does not taste like something that will be beneficial or neutral to beer flavor (filter aids and brewing tools are examples of things that should be flavor-neutral), then it falls on the list of things to remove sooner than later.

Here is an example of how I consider a hop pellet. The aroma is something I want in my beer, unless the hops smell funky (onion/garlic, etc.). So, funky smelling hops may work for early additions because the funky aromas may be removed during the boil. When I taste the hop pellet I get resin, pine, floral, herbal, citrus and bitter flavors that I want in beer. But the longer I ponder the sensation I start to notice astringency on my palate and grassy flavors. And I am thinking these characteristics are of the type I don’t want in beer. So I start by selecting hops that smell nice.

I now stand over my whirlpool looking at the mass of green stuff in the center and wonder what would happen if all of this . . . stuff . . . were in the fermentation vessel instead of laying in the center of the whirlpool vessel. Again I wonder how I would harvest my yeast if this mass of hop and protein matter were intermingled with what is normally smooth and creamy yeast awaiting harvest at the bottom of my fermenter, but that’s a different question for another day. The trub smells a lot like hoppy wort because it is surrounded by hoppy wort. When the trub is sampled, however, the thing that really hits the palate is astringency. Not real sure I want this in my fermenter; what is the return on my investment? Is it an extra bottle or two of beer per 5-gallon (19-L) batch? That’s not a bad proposition, but will the added yield improve, detract or have no influence on the finished beer?

I find this type of thinking to be very useful when thinking about brewing because at the end of the day it’s about beer flavor. Even in a commercial brewery, the financial gains can only seriously be considered if process changes geared towards increases in yield have no obvious negative effects on beer flavor.

Although I believe your beer would taste better if you separated your clear wort from hop solids and trub prior to fermentation, you have pinpointed a very real opportunity for improvements in minimizing wort loss. Almost every commercial brewery these days owns whirlpool vessels to facilitate the separation of these solids from wort. A problem that is becoming more and more significant is wort loss associated with high gravity, highly pellet-hopped batches. Whirlpool wort losses are generally higher when wort gravity increases and when hopping rates are increased, and these two factors are becoming increasingly common as the popularity of high-alcohol, highly-hopped beers continues to grow. If this trend holds, brewers will certainly be looking towards technologies to reduce whirlpool losses. Some of the larger lager brewers have been using decanting centrifuges to address this problem, and this technology will most certainly soon spread.

Response by Ashton Lewis.