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The equations I've looked at so far don't really account for massive late hopping and whirlpool additions. I really like the flavor and aroma I get from late hopping, but It's been very hard to brew a consistent beer. I realize that none of these equations is very accurate to begin with, but from a recipe design standpoint I really need a way to estimate how much bitterness I'll end up with. How do I (somewhat) estimate the bitterness impact of super late additions?

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Excellent question. Similarly, It seems like even in the last 2-3 years, I hear of more guys who let their wort sit, unchilled for 20-30 min after flameout with steeping hops before turning on the chiller. Mike McDole does this I believe. What effect that process has on IBUs, I dunno. –  Graham Dec 20 '11 at 13:30
    
I've decided to have a beer and attempt this one myself. Found a great thesis on hop utilization at different temps here: link –  dana Dec 20 '11 at 23:23
    
You are not getting much bitterness from these types of additions so it really shouldn't matter much what the IBUs are as they are single digit contributions. The consistency part of the deal is knowing the alpha used ounces. Its fairly reproducible for me. –  brewchez Dec 22 '11 at 23:00
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1 Answer 1

For whirlpool hops, you don't have to worry about increasing the IBUs since the alpha acids are barely soluble in their natural state, and contribute bitterness only by being continually boiled.

For late additions, since these are boiled, then the usual IBU formulae can be used. John Palmer gives Tinseth's formula and computed values for a variety of times and SGs. There's also a discussion of the formula from 'Designing Great Beers' by Ray Daniels here on HB stackexchange. For additions less than 10 minutes, 0.06 utilization is assumed. (The link gives the formula so you can compensate also for gravity if above 1.050.)

But as the OP mentions, none of the formulae are accurate. They are best used as a rough guide, which you then refine by inspection of the final result, and adjusting the amount of late additions accordingly. One thing to bear in mind is that it's believed that utilization decreases as more hop mass is added, but the current formulae don't take this into account.

Links:

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Agreed. Worrying about IBUs from late hopping and whirlpooling is a little senseless, because regardless of what formula you chose the contribution is very little. –  brewchez Dec 22 '11 at 22:58
    
you're right - with regular recipes, where the bulk of the IBUs come from 60/90 min additions, the contribution of late hop additions is usually small - just a percent or two of total IBUs at most. But, for entirely late-hopped brews the contribution is then the entire bitterness load - some brews have all their hops added no earlier than 20mins (e.g. 20/5/1), and yet need to hit 30-40 IBUs. I'm not saying to not worry about the contribution of the late additions, but simply that it's highly variable and best addressed through trial and error. –  mdma Dec 22 '11 at 23:57
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