Hop Utilization of Whirlpool Additions

[Powers]

I have long been trying to find an estimate of the apparent bitterness contribution from flameout hop additions. Most of the software I see in the market attributes such additions with zero IBUs, however my Siebel-instructed partner tells me they generally say that 100% of the bitterness will be achieved from any hop addition, regardless of when it is added to the kettle. In other words, they are theorizing that flameout hops are imparting their full bittering value to the beer, but still contributing flavor and aroma.

Is anyone assuming a full IBU contribution from flameout hops, or are you just counting them as "0" while recognizing the bittering contribution is occurring? On the ground, as anyone moved away from the standard bittering addition for brews like IPAs and other heavily late-hopped brews?

Any input is appreciated!

Marcus

[JustinL]

We count it as zero when using pellets.

he may be talking about an extract

[fa50driver]

I haven't quantified the actual contribution of bitterness from whirlpool additions, but from my own experience I can certainly agree that it is significant (for my system.) For some of my moderately hopped beers (lager/pale ale) I don't even add hops until the last 15 minutes, since between whirlpool, rest, and knockout, there is considerable contact time with hot wort.

I sent my first few beers out to a lab to get tested for IBU content, so when designing new beers I basically just mimic the hop additions of current recipes instead of building them from software which I have found to be somewhat useless in calculating bitterness from late hop additions.

[BelgianBrews]

I calculate my whirlpool additions to be at 13% hop utilization with pellet hops. This is an estimated guess, but I have been using this number for a couple years in my recipe development and I think it is fairly accurate with my current system. I also am a huge fan of hop aroma and flavor, but not of bitterness. So a lot of my beers have a substantial amount of whirlpool hops. I recently made an IPA with 20 IBUs (according to my numbers) coming from whirlpool. My total calculated IBUs for this beer is 50. The beer tastes like 50 IBU, maybe even closer to 60. It is certainly not 30 IBU.

I believe that larger systems would likely result in more utilization, as would a more turbulent whirlpool, longer whirlpool time, longer settling time, and longer transfer time. Using whole leaf hops should result in lower isomerization than pellet hops, because whole leaf hops have decreased surface area.

[MikeS]

I used to work at a pretty large regional brewery and we would do IBU tests on all of our worts, as well as finished beer.

Every once in a while there would be situations where the hop dosing systems failed to pump all the hops (pellets, as a slurry with wort) in for an addition or an absent-minded brewer would neglect to add the whirlpool hops at the correct time.

As a result of these "forbidden experiments" we came to the conclusion that no matter when the hops are added, we were getting 100% utilization.

At the *much* smaller brewery I now run, we have no such luxuries as a full-on QC lab. I run the numbers through Promash to get a general idea of bitterness levels, but I'm under no illusion that those are *actual* IBU numbers. I count on sensory analysis to tell me the bitterness is right and find the computer program's calculations allow me to get reasonably close when tweeking recipes or a new batch of hops comes in, etc.

On a related note, it always made me chuckle when folks would put IBU numbers on their labels that were obviously calculated, rather than measured, values. We would run IBU tests on a lot of these beers and the actual and stated IBUs were all over the place. This was also during the "race to 100 IBU" days and most of those beers were wildly off their stated values.

Cheers- Mike

[brewmaster 2011]

In order to count twords more ibu's the oil must first Isomerize. The hop oils will still desolve with out isomerizing.

[BelgianBrews]

I am curious as to how folks are getting 100% utilization. I have always been taught that maximum isomerization with pellet and whole leaf hops is in the range of 30-33%. There is very little difference in isomerization levels when boiling a hop for 90 minutes versus 60 minutes. In saying '100% utilization' I am assuming you mean that you are getting 30-33% isomerization. Please correct me if I am wrong!

[dick murton]

The utilisation depends very much on the hops you are using, the kettle design and boil duration, and when exactly you add the late hops, and how long the hot wort stands on the hops whilst in the whirlpool / hop back / copper, even if not being boiled, wort pH, wort gravity and probably some other points I have missed.

Rule of thumb, as quoted elsewhere, for "normal" pellet or whole hops - say 30 to 35 %, though at one little brewpub, we seem to get closer to 45 % (lab measurement) for hops added at start of boil (60 minutes). Late hop utilisation varies for about 10 % up to 20 %, roughly according to contact / stand time. Even if using pre-isomerised hop pellets, utilisation will only be about 55 to 60 %. And unisomerised extract appears to be about the same as unisomerised whole or pellet hops.

Because of the utilisation of late hops, if using high alpha hops (because of desired aroma), it can be necessary to add them all just a few minutes before end of boil, or the bitterness goes through the roof.

Hop utilisation is expressed as IBU achieved / input ppm of alpha acid.

[MikeS]

I am curious as to how folks are getting 100% utilization. I have always been taught that maximum isomerization with pellet and whole leaf hops is in the range of 30-33%. There is very little difference in isomerization levels when boiling a hop for 90 minutes versus 60 minutes. In saying '100% utilization' I am assuming you mean that you are getting 30-33% isomerization. Please correct me if I am wrong!

Totally right...

Pardon the confusion, but when I said "100%" I really meant "all of it."

We were getting about 35%, regardless of the time of addition.

-Mike

[drewseslu]

My presumed hop utilization on a 30bbl NSI brewhouse.
FWH 40-30%
Mid boil 25-15%
WP 10-18%
Hopback 5%
The ranges cover from low ABV & IBU brews up through DIPAs and ABWs.

[anthonybaraff]

I haven't quantified the actual contribution of bitterness from whirlpool additions, but from my own experience I can certainly agree that it is significant (for my system.) For some of my moderately hopped beers (lager/pale ale) I don't even add hops until the last 15 minutes, since between whirlpool, rest, and knockout, there is considerable contact time with hot wort.

I sent my first few beers out to a lab to get tested for IBU content, so when designing new beers I basically just mimic the hop additions of current recipes instead of building them from software which I have found to be somewhat useless in calculating bitterness from late hop additions.

I'm trying to estimate the IBU contribution of 2.1kg (4.6 lbs) of 10.5 AA hops added in the whirlpool to 2000l (17bbl) of 1.053 wort on a system where the brewers normally only do bittering additions. If these hops were boiled for 20 minutes the software would suggest that they will contribute about 24IBU vs 8 IBU for a 5 minuteboil. If I'm aiming for 30 IBU. How much more would you add (IBUs) for bittering?

[Alex T]

My experience is that hops added during whirlpool will still give you around net 20% utilisation (wort to final beer). So a lot of bitterness can still come from there.... I find on this topic "the books" generally don't match up to reality - they always say isomerisation happens at "100degC", but even when using a hopback where the wort is probably more like 95degC you pick up a lot of bitterness. All depends on the system....

Cheers,

Alex

[BeerCityChamp]

Isomerizing

Any time you strike hops above 185 degrees, you are isomerizing alpha acids. Therefore, I would count every IBU even after flame out... I know of IPA's that are 60+ IBU's with only additions during whirlpool.

[Baldrick]

Why do so many disregard the contribution of beta acids to overall bitterness?

Beta acids are bitter to begin with. So the perceived bitterness would rise even though the IBU count will not. IBU's are measured via spectrophotometry of a sample prepared in a solution of isooctane and measured at 275 nm so if the bitter compound is not an isomerised alpha acid, then it may not be measurable via that standardised method.

I don't buy the 100% utilisation in the whirlpool story - isomerisation of alpha acids takes time. So you may get some isomerisation due to the contact time and elevated temperatures during whirlpool and transfer, but once the grub pile settles to the bottom of the kettle, you've not got very much contact surface area between hop particles and wort, so the utilisation during transfer is very much diminished.

[Baldrick]

Finding out the IBUs in finished beer is a simple and well documented process.
Any analytical lab could do it, and most universities have the capability and would gladly take a sample for analysis. If the local university's Chemical Engineering faculty has a brewing sciences department it makes this all that much more simple.

IBUs are measured via spectrophotometry. The standard is absorption of ultraviolet light at a wavelength 275 nm of a sample prepared in the solvent iso-octane.

If you're wondering what the contribution of bittering is in the whirlpool this is an easy way to find out.

However, I've found that the determination of IBU numbers is at best academic, and at worst an act of machismo to see what sort of "numbers" can be generated to satisfy the beer geeks in your audience. "Hey I made a beer that's 180 IBUs (calculated)". Greeeaaat..…I'm happy for you. Thanks, I'll pass on that.

IBUs are not the same as apparent or real bitterness. IBUs are a documented set of procedures to measure isomerised alpha acids dissolved in finished beer via the spectrophotographic method. It's not the same as perceived bitterness, nor is it the same as actual bitterness, which comes from roasted malts, bitter essential oils, hop beta acids (which no one ever seems to take into account) and other sources that are impossible to determine.