Actual Hop Utilisation in the Whirlpool

[micblair]

Following ASBC method for determination of bitterness in Wort via UV/VIS, I set about comparing calculated to observed bitterness.

The brew itself was 23.5L batch of Altbier (OG =1.045), brewed on a Braumeister, with two hop additions of German Spalt (aa 5.9%). My version of BeerAlchemy can not calculate whirlpool/hop-steep bitterness, so the bitterness calculated for two hop additions at 60 min and 0 mins (15 minute hop-steep at ca. 95C before being sent to a heat exchange) are as follows:

Calculated values, Tinsenth

• 60 min, 45 g of German Spalt aa 5.9% = 31 IBU
• 0 min, 55 g of German Spalt aa 5.9% = 0 IBU

The measure values for wort samples collected at the end of the boil and the end of a hop-stand are as follows:

• Measured bitterness at 60 min = 29.91 IBU
• Measured bitterness 15 min hop steep = 41.50 IBU

Therefore bitterness contribution from a single 55g whirlpool addition = 11.59 IBU

Calculating the utilisation for 60 minute addition are as follows:

% utilisation = (BU, mg/L x brew length, L)/ Hops reqd, g x %aa in hops

% utilisation = 29.91 mg/L x 23.5 L x 1g/ 45g x 0.059 x 1000 mg = 26.47 %

Calculating the utilisation for a whirlpool/15 minute hop-steep addition are as follows:

% utilisation = (BU, mg/L x brew length, L)/ Hops reqd, g x %aa in hops

% utilisation = 11.59 mg/L x 23.5 L x 1g/ 55g x 0.059 x 1000 mg = 8.39 %

 

[///]

Just skimming across, I know from my testing in a photospectrometer i get between 30-70% of total BU from the whirlpool. Its hops and type of beer depending.

MyGolden Ale I get 20BU's for the hops used, so only add 5BU worth at the start of the boil. In my IPA and Pale I get 30% of total BU.

The BU's would also alter if using a wort pack, it is all about time and heat.

 

[micblair]

Sounds like a lot, no chill?

 

[jlm]

Interesting Scotty, that's on the work brewery I assume? I'm currently working on my first recipe that will be sold commercially (a one off for the mob I work for) and as a rule of thumb anything that goes in the kettle at flame out/whirlpool is calculated at 20%. So with 1250g (most of which has a high alpha %) thrown into 800L at flame out I was surprised how much of my target IBU was eaten up with that addition.

 

[slash22000]

Seems to fall in line with the generally accepted estimate of ~10% utilisation (~12 minutes boil) for whirlpool/hop stand on the home brew scale. Would love to see more results in the future!

 

[technobabble66]

Apologies if i'm being a bit of a thickee here, but:

Are you all saying you calculate additional IBUs generated by a Whirlpool/Flameout addition by just adding the IBUs of the W/F addition as if it had been boiled for ~12mins? [or doing a BU calculation for only that addition?]
How does this approximation account for the contribution of the prior additions? (i appreciate the 60min addition may not contribute much more, but a large 10 or 20 min addition could contribute a lot of IBUs).
Or do you just add 12mins onto every addition?

Also, how does knowing the %utilisation help me calculate the IBUs generated by the various additions - in, say, Ianh's spreadsheet?
Do you simply manipulate the equation in micblair's post to be:

BU, mg/L = (% utilisation x Hops reqd, g x %aa in hops) / ( brew length, L)


and therefore just stick micblair's experimental result, 8.36%, into the % utilisation to get an idea of the IBUs your W/F addition is contributing?

 

[micblair]

Hey Technobabble, this was a two-hop addition beer, i.e. 60 minute remaining in the boil (at which point I removed a sample to determine bitterness by UV/VIS) and the second addition at 0 min left in the boil, whereby I steeped for 15 minutes.

The difference between the additions (41.50 - 29.91 IBU = 11.59 IBU) allows you to arrive at the bitterness contribution from the whirlpool hopping alone.

And yes, rearrange the equation making sure the units are in mg's and litres. If you haven't been calculating bitterness from a whirlpool because of lack data, this should help.

 

[slash22000]

Are you all saying you calculate additional IBUs generated by a Whirlpool/Flameout addition by just adding the IBUs of the W/F addition as if it had been boiled for ~12mins? [or doing a BU calculation for only that addition?]
How does this approximation account for the contribution of the prior additions? (i appreciate the 60min addition may not contribute much more, but a large 10 or 20 min addition could contribute a lot of IBUs).
Or do you just add 12mins onto every addition?

12 minutes to every addition (assuming ~10% utilisation). When you are doing a whirlpool/hop stand you are keeping your wort at a high temperature and it will continue to effect every hop addition, not just the ones you throw in at 0 minutes.

Yes, this makes a pretty huge difference to the final bitterness of the beer. 20 minute additions become 32 minute additions, for example. The obvious solution is to subtract 12 minutes from the boil time of each addition to account for the extra bitterness. Obviously this means that 5 minute additions etc become impossible (since your minimum is 12 minutes), meaning you might have to reduce your 60 minute (48 minute?) addition to account. Obviously do not reduce your flavour/aroma additions, you want all that hop goodness in the beer.

 

[technobabble66]

Thanks micblair & slash,

Yes, i'm very keen to know the IBU contribution of the W/F addition, and the bittering impact of the 15-20min stand after Flameout. Most of my hops additions have been 20-0 mins, so the extra 5-20mins of steeping makes a huge difference.

@micblair - of course! the 60min addition would contribute little more, so the BU increase is basically due to your W/F addition. Silly me! ^_^

@Slash - Yeah, 12mins to all makes more sense. And adding 12mins to my IBU calc's is going to be much easier to correct for in my spreadsheets.

Wow - it's a massive difference. I don't know how i'm going to squeeze all my hops in without making it all super bitter!

 

[slash22000]

You will only get bitterness from the hops while the wort is >85ºC. If you want to add more flame out hops without adding bitterness, wait until the wort is below that temperature, chuck them in, and let them sit for a little while.

Alternatively, brew 100+ IBU double IPA's! You can only get so much bitterness out of hops and ~100 IBU seems to be the limit, so it doesn't matter how much more hops you add for flavour/aroma! Chuck in 10,000 IBU worth of hops, no worries.

 

[micblair]

Just in case you thought I was making this up! Here's a photo of some centrifuged wort samples.

 

[RelaxedBrewer]

Great stuff.

I think it would be really interesting to measure the IBUs from different whirlpool steep lengths.
Let the hops steep for up to half an hour while taking a sample out every 5 minutes and cooling it.
Even better if you took temperature reading of the wort for each sample.

This would give great information on hop utilisation at different temperatures.

 

[micblair]

Great stuff.

I think it would be really interesting to measure the IBUs from different whirlpool steep lengths.
Let the hops steep for up to half an hour while taking a sample out every 5 minutes and cooling it.
Even better if you took temperature reading of the wort for each sample.

This would give great information on hop utilisation at different temperatures.

Prepping the samples is quite a mission as you have to do 15 mins of centrifugation, bunch of pipetting and then 15 minutes on a shaking table, followed by more centrifugation (to split the isooctane away from the acidified wort). The running the UV-VIS part is fairly quick. I agree though, you could generate some nice hop isomerisation kinetic data so you could steep as long or as little with a full understanding on the effect of bitterness. Will be interesting to see what the bitterness of beer turns out to be.

 

[adamh]

i wish i didn't read this on a Friday afternoon :blink:

Much better suited for Tuesday reading :lol:

 

[micblair]

Just skimming across, I know from my testing in a photospectrometer i get between 30-70% of total BU from the whirlpool. Its hops and type of beer depending.

MyGolden Ale I get 20BU's for the hops used, so only add 5BU worth at the start of the boil. In my IPA and Pale I get 30% of total BU.

The BU's would also alter if using a wort pack, it is all about time and heat.

Hey Scotty, you're whirlpool times and knockout times at Rocks are probably a lot greater than those employed by a home brewer right, and perhaps explains your higher utilisation?


Something like:
15-20 minute whirlpool
15-30 minute rest
min. 60 minute knockout to cellar

 

[///]

Hey Scotty, you're whirlpool times and knockout times at Rocks are probably a lot greater than those employed by a home brewer right, and perhaps explains your higher utilisation?


Something like:
15-20 minute whirlpool
15-30 minute rest
min. 60 minute knockout to cellar

Actually less, 10 mins WP, 5 min rest and out you go. Takes 45 mins thru heat ex. We don't muck around as the next batch has to go in ...