Hop Steep IBU contribution

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Corbières

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This is the hop schedule for a recipe I found online.
Is there an error in not counting the IBU’s contributed by the two STEEP additions, or am I not understanding something?
The recipe quotes total IBU 21.25


HOPS (g)
GALAXY 6 Boil 60 Mins. IBU 13.75
GALAXY 6 Boil 10 Mins. IBU 5
MOSAIC 5 Boil 10 Mins. IBU 2.5
GALAXY 25 Steep 60 Mins
MOSAIC 25 Steep 60 Mins
 
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This is the hop schedule for a recipe I found online.
Is there an error in not counting the IBU’s contributed by the two STEEP additions, or am I not understanding something?
The recipe quotes total IBU 21.25


HOPS (g)
GALAXY 6 Boil 60 Mins. IBU 13.75
GALAXY 6 Boil 10 Mins. IBU 5
MOSAIC 5 Boil 10 Mins. IBU 2.5
GALAXY 25 Steep 60 Mins
MOSAIC 25 Steep 60 Mins
That's no error, but I see how one could think that! Historically, the thinking was that the bitterness in Alpha Acids are produced from the hops during boiling, so if the wort isn't boiling, no IBU's are added. With this in mind, calculators that measure IBU's use a few different formulas that adhere to this thinking, with the most common (arguably standard) being Glen Tinseth's formula from Brewing Techniques. Jan/Feb 1994.

In reality, steeping close to boiling does produce IBU's. According to John Palmer, you should take 40% of the calculated bitterness from boiling for that amount of time for steeping. From How To Brew, "This is based upon a study by Malowicki and Shellhammer (2005) that showed the amount of isomerization at 194°F (90°C) is roughly 40% of that at 212°F (100°C); this fell to about 15% at 176°F (80°C)."

Once I find a formula where IBU's are included from steeping that is a bit more accurate, I'll put it on my website.
 
Thanks for the replies

Plugged into Brewfather at 80c - it does add on ibu’s ?? In the above extent it added 4 IBU @ 80c

Even lowering the steep temp it continues to add to a lesser extent.
 
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In reality, steeping close to boiling does produce IBU's. According to John Palmer, you should take 40% of the calculated bitterness from boiling for that amount of time for steeping. From How To Brew, "This is based upon a study by Malowicki and Shellhammer (2005) that showed the amount of isomerization at 194°F (90°C) is roughly 40% of that at 212°F (100°C); this fell to about 15% at 176°F (80°C)."
Yes this looks like what Brewfather is doing 👍🏻
 
Thanks for the replies ??

Plugged into Brewfather at 80c - it does add on ibu’s ?? In the above extent it added 4 IBU @ 80c

Even lowering the steep temp it continues to add to a lesser extent.

That sounds about right. As @NotSure mentioned, there will still be some isomerisation at lower temperatures but it happens at a much reduced rate. 60 minutes is actually quite a long steep (I normally go for 30 minutes on my recipes) so that will up the amount of IBUs slightly.
 
Devils advocate here
What about that suggestion of Perceived bitterness coming in to play as believed it can happen with dry hopping and whirlpooling?
 
Devils advocate here
What about that suggestion of Perceived bitterness coming in to play as believed it can happen with dry hopping and whirlpooling?

That's a big can of worms you're opening there!

As I understand it, you do get some additional perceived bitterness from dry hopping but there doesn't seem to be a way to calculate it like you would for boil additions.
 
Devils advocate here
What about that suggestion of Perceived bitterness coming in to play as believed it can happen with dry hopping and whirlpooling?
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I agree Stu I was just I was just seeing if we got some of the boffins throwing in but in reality I think this thread has got it spot on as you can go on forever with IBU calculating and perceived bitterness.
I am of the same thinking that is not theoretically absolutely correct but is near enough that it can be relied on to be there or there abouts
 
Once I find a formula where IBU's are included from steeping that is a bit more accurate, I'll put it on my website.

Here is a decent rough approximation. Source is me. Call it the Taylor equation if you want... or don't, I don't really care. I'll even convert it into grams and liters for you. Please, play around with it, see what you think. I'll listen to feedback. Maybe I need to increase the 7.5 divisor, the result certainly being only good to about one significant digit, not really two digits. It's an estimation, which I think is reasonably accurate, and better than nothing.

https://www.thehomebrewforum.co.uk/threads/hop-utilisation.97728/#post-1111237
or:

IBU = grams * AA% * sqrt(2*HStime) / V / 7.5

where
V is post-boil volume in liters,
Boiltime is in minutes, and
HStime is post-boil hop stand time in minutes where it hangs around between about 65-90C.

By the way... Isomerization doesn't magically quit at 80C. It's just quite slow below that point. There's still isomerization happening down to like 60C or thereabouts.

Cheers.
 
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You can spend a lot of time worrying about IBUs but a lot of it will depend on your taste buds, personally I struggle to taste the difference +/- 5-10 IBU.

To throw a further a spanner in the works - you don't state the AA value of each of your hops. That can make as much difference to the IBU as the times you put them in, as the AA can vary greatly from crop-to crop and region grown. Recipes that just list the hops without an AA value can be very inaccurate e.g. that first addition of Galaxy, the target is 13.75 IBU from that addition and the recipe suggests 6g, but if you used some Galaxy with a lower AA you'd need more hops to hit 13.75, and vice-versa. Welcome to the rabbit-hole of brewing.
 
To throw a further a spanner in the works - you don't state the AA value of each of your hops.
Sorry yes your right - but total IBU’s are given so can be worked out fairly easily.
It’s not my recipe btw - I found it online and was checking my own understanding of hop steep contributions compared to what Brewfather tells me is happening.
Cheers 👍🏼
 
Perceived bitterness depends on many things so I wouldn’t try to figure that out, just make adjustments next time you brew the recipe.

The bitterness you get from whirlpooling though is real and depends on the temperature and duration. You get about half the bitterness at 90C as you do for the same duration at 100C. At 80C it’s about a quarter, and at 70C about 10%.
 
I can tell the difference between IBU's as I am quite intolerant to IBU's but I am probably in the minority and that's why I do mainly whirlpooling to cut it down but still get the flavour from larger hoppage.
I have even done whirlpooling only at below 70c when they say that you do not get isomerisation of hops but I can assure you that you do get IBU/Perceived bitterness from them that's why I was playing devils advocate as the consensus of opinion is that you do not get bittering from sub 70c well I can assure you that you do and it is either isomerisation which is said not to be possible or perceived bitterness.
Sorry can of worms opened
Ps the bitterness is not usually too high for me with this method though so most people would not find too much to shout about
 
I have even done whirlpooling only at below 70c when they say that you do not get isomerisation of hops
You do get isomerisation at lower temperatures, down to about 40C I believe but the rate of isomerisation drops dramatically so for all practical purposes below 60C (4%) can be ignored.
 
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