Hop bitterness calculations.

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Top Cat
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Hop bitterness calculations.

Post by Top Cat » Tue Nov 07, 2017 10:05 pm

Hi Guys.
I wondered if anyone could help me?
I am trying to get a rule of thumb calculation for IBU/EBU values. I know the following are influential but need a SIMPLE formula for calculating.
AAU's as a percentage of the hop.
Weight.
Boil time.
Gravity of my wort.
Quantity in gallons of my wort.
I don't think I've omitted anything critical, I just need something as a guideline without referring to long equations or charts etc.

Jambo
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Re: Hop bitterness calculations.

Post by Jambo » Tue Nov 07, 2017 10:57 pm

Palmer's how to brew suggests this:

IBU = AAU * U * 75 / V

Where
AAU = hop AA % x hop weight in oz
U = utilisation
V = volume in US gallons (3.8 L)

Utilisation is complicated and you need to refer to a chart of gravity and boil time to get a good number but if you brew 'normal' ales and refuse to look at charts then 0.25 looks like a good ballpark number.

Hope this helps

richard080561
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Re: Hop bitterness calculations.

Post by richard080561 » Tue Nov 07, 2017 11:00 pm

I don't think there is a simple answer. Ray Daniels in 'Designing Great Beers' takes a few pages to explain it with a few forumlae and a table
Richard M
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Jambo
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Re: Hop bitterness calculations.

Post by Jambo » Tue Nov 07, 2017 11:05 pm

Simplifying a bit, maybe you could use this as a really rough rule of thumb assuming an average strength ale, with volume in L:

IBU = AAU * 70 / V

I'd be inclined to use charts for utilisation myself though!

Top Cat
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Re: Hop bitterness calculations.

Post by Top Cat » Wed Nov 08, 2017 11:07 am

Thanks for the replies Guys.
I thought there wouldn't be a simple answer, I suppose finding the utilisation is the hard bit, I do have John Palmers book/"encyclopedia". Unless I need to be pretty accurate, I think I will go along with Jambo's idea.

Jambo
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Re: Hop bitterness calculations.

Post by Jambo » Wed Nov 08, 2017 11:57 am

Just realised if you always brew 23L batches then you can call it
IBU = AAU * 3

I'm not sure you can make it more simple than that :)

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Kev888
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Re: Hop bitterness calculations.

Post by Kev888 » Wed Nov 08, 2017 2:19 pm

As you say, there are a number of factors that determine the bitterness units; simple calculations aren't going to give a highly accurate figure, but then (to my knowledge) even the complex ones are still just estimates. From memory, the calculation I used involved empirically derived numbers to provide a 'bigness' (or gravity) factor and 'time' factor, which could then be used to estimate utilisation; but unfortunately I don't recall the source of this.

Though our ability to accurately perceive the IBUs isn't perfect either, and I understand even lab measurement of them can vary between labs/methods for the same sample. Bring in that hop Alpha Acids aren't the only bitter compound imparted by hops and that there are different opinions on how these change during storage.. and both the initial and final conditions may not be quite as concrete as imagined, let alone the utilisation calculation.
Kev

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basswulf
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Re: Hop bitterness calculations.

Post by basswulf » Wed Nov 15, 2017 5:47 pm

Somehow replied to the wrong thread! Whoops!

Wulf

Cobnut

Re: Hop bitterness calculations.

Post by Cobnut » Wed Nov 15, 2017 6:24 pm

This is a good explanation. http://brewinreview.com/home-brew/home- ... alculator/

Doesn't necessarily give you an easy way to calculate it, but there are plenty of spreadsheet calculators and the like out there. I use this one:

http://www.yobrew.co.uk/petes_yobrew_be ... s_v1_7.xls

It's not mine btw, but I found it a couple of years back and now sue it as a repository and record for my brewing...I started with extract and now BIAB.

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