Let's begin this discussion by asking a few questions in an order to explain it better. Do you chuck the trub from your fermenter after you are done bottling/kegging? Does it hurt your conscience, emptying the dry hop bag down the drain? After maybe only using a third of their potential? Also those expensive but spent yeasts... are they worth nothing?
Breweries are a smart bunch. They employ many tricks to save money on brewing
Before I begin let me admit this is a popular trick used by craft/commercial breweries for ages and I am not the original inventor of reusing spent yeast - however with spent hops I have never seen a brewery trying it, I guess the multi stage filtration they use makes it difficult to do.
Research at Oregon State University recently revealed that discarded hops utilised for dry hopping are still rich in compounds brewers covet.
The numbers are downright stunning. Dean Hauser, and others at Oregon State, examined multiple lots of Amarillo, Cascade, and Centennial hops.
As per studies:
Overall, spent dry hops retained 77 percent of alpha acids.
Overall, spent dry hops retained 51 percent of total oil.
In the next section of the blog I am going to discuss some basics of homebrewing to explain what we are actually planning to do, if you are a seasoned brewer, please fast forward to “The Tip” section of this article. If not or still interested, by all means continue.
Some Background
To keep this article palpable for everyone and to the point I am going to use minimal scientific terms and micro-details. For those who fancy reading geeky stuff about beer brewing I suggest checking these links.
The Molecular Biology of Fruity and Floral Aromas in Beer (and other alcoholic beverages)
What are Hops?
Hops in a nutshell are extremely fragrant flowers and very versatile being at that. They contain some of the most complex and densest aroma - flavour mix known to nature, only second to roasted Cacao seeds but more so than even Vanilla pods. Curiously hops are closely related to Cannabis - another complex plant species in that department.
Hops are responsible for providing three essential characters to your beer: aroma, flavour and taste(bitterness). Types of yeast strains and malts do contribute to these characters and we definitely don't want to undermine that factor but that's a subject for another discussion. Also Hops these days are more commonly utilised in your beer recipes in such a way, to absolutely cash in on these characters.
To further explain hop's functions in brewing, most of hop’s aroma compounds quickly dissipate when boiled. Flavouring compounds follow at slightly slower rate but much of them also bid farewell when you boil a wort slightly longer. Bittering compounds benefit from longer boils and they seem to survive high temperatures for longer durations. However they are highly oxidation prone - another subject, probably we will cover in another blog.
Most likely, all of the beer recipes you may see - have an orthodox hop addition schedule. You may notice the bellow parameters in most recipes.
A Typical Hop Schedule in Beer Recipes
Aroma hops: 30 to 0 minutes left to boil end and/or shorter hop stands or dry hopping
Flavouring hops: 45 to 5 minutes left to boil and/or long hop stands
Bittering hops: 120-30 minutes to boil end
***Dual purpose hops can be added at any stage of boil or fermentation.
What is Trub?
Trub collected in a glass after an IPA session. The green stuff is hop particles. Many brewers believe that hop bags are a waste of time, money and even hops!
The mucky, outrageous looking gunk sitting at the bottom of your fermenter is called trub. It may look unappetizing but it contains a perfect mixture of goodies for your next batch of live yeast to thrive. These dead yeasties (a huge portion still alive) contain a wide range of B-vitamins, potassium, essential trace minerals (selenium, molybdenum, zinc etc) and nitrogen sources that live yeasts readily feed upon. On a regular brew day, you add yeast nutrients (most likely DAP) by providing maybe only active nitrogen contents for your yeasts to cop with.
What is Krausen?
After the first couple of days of vigorous fermentation, once the foamy top settles down, you'll notice a thick green ring still clinging to the walls of your fermenter. It's called krausen. After you dry hop some of the fine hop particles may escape the hop bag and join the bottom layer of the krausen ring. You are done extracting most of the aroma contents out of the hops in about first three days of dry hopping, but what about the flavour and bittering compounds? You are right, remains still in there.
The Tip
A three-way experiment proves that boiled yeast works better than DAP
The tip is simple. All you need to do is save the trub and content from your dry hop bag; then throw it in your next boil. That being said, you should decide the time of addition by judging the amount/types of hops you have in your trub.
For example; your ex-batch involves heavy dry hopping, if you add it all at 60 minutes you may end up with excessive bitterness and less flavours, especially if dry hopping involved a heavy dose of hops with high Alpha Acids.
To cop with that, you should perform a step addition of trub just like a hop schedule, especially if the previous batch was an IPA or NEIPA. If you made a regular no “dry hop” beer batch you are perfectly good to add the yeast cake near the last 15 minutes of your boiling schedule for yeast nutrition, and perform your regular hop schedule simultaneously.
Now this tweak is probably for guys who have brewed at least a few batches and know what I'm talking about. If you are not a regular/seasoned brewer or worse a first time brewer; do feel free to contact me and I will be happy to design a boil schedule for you.
For obvious reasons, adding trub during boil avoids a chance of adding some of the surviving live yeast cells of your last batch to your next batch; that way also preventing the chance of yeast mutations - which is a separate subject again, but for those who are unfamiliar, for now, discourage yourself from doing that.
Important notes before you try this:
Always turn the flame off when adding the trub to a boil to avoid the chance of an accidental fire due to the small amount of alcohol vapourising quickly from your trub when exposed to high temperatures (an extremely rare chance, but why take a risk?). Turn the flame back on after stirring for a minute.
Always boil with all windows open. This principle stays constant with any kind of cooking/heating process.
Start your next batch as soon as you are done bottling your last. Preferably in a next couple of days. Keep your fermenter closed with airlock on, away from light during this time. Alternatively you can collect the trub in a sanitised airtight container and transfer it to your freezer until the next brew day(not longer than 30 days).
The Krausen sticking on the sidewall of your fermenter after bottling, consists high amount of hop oils and yeasts. You should scrap it off and use it along with the trub.
It takes 3-5 minutes of boil to make sure all of the yeasts from a trub are dead.
When using dead (or alive) yeasts for yeast nutrients you don't have to worry about putting too much. If your yeasts are not able to access most of it, which is by the way highly unlikely, it will just sink at the bottom and form a new trub.
If you do this correctly you can,
Minimize/ignore the addition of flavouring hops
Completely ignore the addition of bittering hops
Completely ignore the addition of yeast nutrients.
This way you can spend more on your dry hops, and come out with fantastic hoppy beers, only to utilise the spent hops for your next batch.
Before ending this article, my apologies to everyone for delaying this post for long. I was caught up with some stuff. And even though I love writing, it takes a considerable amount of time in cross-research and especially editing because of my bad English! :D
Anywhooo...!! I promise the blog posts will be rolling out regularly from now on.
Let me know how you like the results if you try this. Put comments on bellow and share your experience.
Happy homebrewing!
A professional Brewer on her Approach
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