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asnider

Actual IBU vs. Perceived IBU

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I think I already know the answer to this question, but here it is.

I am contemplating doing an Irish stout that would simply be two cans of the Mr. Beer St. Patrick's Irish Stout HME. When plugging this into QBrew it shows a hop profile that is double that of a single can. This makes sense on paper, but doesn't seem "right."

Is this just a case of actual IBU vs perceived IBU, where the actual IBU would indeed be twice as high, but the perceived IBU would be the same as using a single can of HME? Or would the beer actually taste twice as bitter?

:stout:

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Why is that? I thought it would still be balanced, since the malt would also be doubled.

I guess I'll do this differently, maybe adding some dark DME and a hop boil (if necessary) instead of using two cans of HME.

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The way I understand it and the only way I can explain it is this:

IBU is a fixed number. It is what it is. But a stout can have an IBU that is similar or even higher than a Pale Ale, and not seem as bitter.

That's perceived bitterness, and is more a function of the malt/hops relationship. Hops is bittering; malt is sweetening and body/mouthfeel. A brew with less malt - particularly less darker malt - is going to allow the hops bitterness to come through more than a brew with a more complex malt bill. Darker malts and specialty grains, such as chocolate and black patent and crystal 120 give added flavor and a heaviness to a beer that the bitterness of the hops can't fight through as easily as a beer with fewer dark malts, and an SRM of maybe 8 or 12.

In your example, the IBUs are doubled, because they're doubled. That's just the math. But so is the malt bill, so the perception of the bitterness isn't going to be twice as much as a single-can batch.

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"FedoraDave" post=320322 said:

In your example, the IBUs are doubled, because they're doubled. That's just the math. But so is the malt bill, so the perception of the bitterness isn't going to be twice as much as a single-can batch.

That's what I thought. But gophers6 is suggesting otherwise, so now I'm confused!

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I'm confused, too. I'm not an expert on such things; what I wrote was just my understanding of the difference between actual IBU and perceived bitterness. And I'll admit I could be wrong. I just know that IBU doesn't automatically translate to bitter. A lot depends on the malt bill.

I will say that the conversion will not be 1:1 in terms of all the components, and the result may be more bitter than what the un-doubled recipe would be. But it won't be twice as bitter, either. Sadly, there's no formula to calculate perceived bitterness, for obvious reasons.

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Guest System Admin

Hang on!

I have a post that may help but I have to go find it.

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Guest System Admin

OK so I asked Mashani about the doubling effect when I was working with ADIPA and deciding whether or not to split the batch. His reply was really helpful so here it is:

To clarify a few things. Each can of ADIPA is 29 IBUs. So if you use both you have 58 IBUs.

IBUs are a measure of "bitterness", not "hoppyness" in the sense of flavor and aroma. 29 IBUs is 29 IBUs, regardless of whether the hops it came from were added as a early (bittering only boil) or if they came from a late addition which left behind flavor and/or aroma as well as bitterness. In either case they still balance out the malt, and it's still just as "bitter". Sometimes you get a bit of an initial "bite", a slightly more "harsh" kind of note from a long boil hop addition that you don't get from a late addition, but measurably it's the same IBUs, and it balances the malt sweetness just as much overall.

So, if ADIPA isn't perceived as "hoppy" (which it isn't really) that is because most of the 29 IBUs per can came from a longer bittering only boil, vs. larger flavor/aroma additions (as in it was not "hop bursted" like some of us like to do to get more flavor/aroma).

But the 29 IBUs per can are still 29 IBUs. The bitterness if 29 IBUs is THE SAME no matter where the hops were added. Just the flavor/aroma changes. Hop flavor is NOT hop bitterness, and has no direct relationship to IBUs beyond whatever bittering compounds happen to be extracted by those late additions and added to the early boil IBUs.

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I think he was asking if the 100 IBU's were going to be awfully bitter if he used 2 St Pat's Irish Stout HME's in one 2.5 gallon batch.

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This is my IMHO.

To me, the new St. Patricks has enough IBUs to add a full pound of malt and still be balanced. More even depending on your tastes and what your going for. It depends on if you are trying to go for more of a bitter dry irish stout or something with more robust body and less bitterness.

I'd personally add more malt instead of doubling up the cans, unless I was trying to turn it into a 1.07+ish Imperial Stout. Then 2 cans + more malt might be appropriate.

IBUs are IBUs. Fedora Dave is right in that the malt bill directly affects how you will perceive them. There is also a point where you simply stop tasting "more bitter" as "more bitter". IE 200 IBUs and 100 IBUS or even 80 IBUs might taste exactly the same to you. This varies by individual. So you may like it and other may hate it. Hard to say. This is really subjective to an individual, and also your tastes will change over time - if you drink a lot of bitter beer, your tastes will adapt. At least many peoples will. If you are a "super taster" of bitter, then you may never ever like bitter beer...

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Excellent replies, and good find on that previous post, Wings.

Unfortunately, it doesn't answer the question that I think asnider was asking originally, because only asnider can answer it. Specifically, will the beer he's proposing be too bitter? Mashani is correct when he says to some people, yes, it will be, and to others, no, it won't.

The IBUs are definitely doubled no matter who you are. But the bitterness perception is going to change from person to person. There are no definitive answers when it comes to the subjective topic of taste. The only way for asnider to get his answer is to brew the beer and see what he thinks of it.

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Another thing to consider is the "bitterness ratio." BU/GU. IBU/SG. Call it what you want. It's a measure of the beer's perceived bitterness.

You take the IBU and divide by the decimal portion of the OG. In theory. 0.5 is balanced. If you get over 1.0, it's getting bitter. So, a 1.060 beer with 30 IBU is balanced (30/60 = .5), while a 1.060 beer with 60 IBU is bitter (60/60 = 1.0).

In the example of the OP, the two-can Stout should be perceived equally as bitter as a one-can version, because while the IBU doubles, so does the OG. The bitterness ratio remains the same.

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I recall reading about BU/GU, but I didn't understand it or appreciate it at the time. Or maybe it wasn't explained as well then. Or both.

But this makes it much clearer, and could become something I'll use when formulating recipes. Excellent post, Crazy.

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First, which cans of St. Patricks are we talking about? Old 1.21 lb cans or the new larger refills.

For the older cans, I alway thought that the HMEs were basically "designed" so that when one can of HME and one can of LME were used together, the resulting batch came out the way Mr.B intended. The can of HME has enough hop bitterness to balance the malt contained in the HME and the LME. If two cans of HME are used together for a standard sized batch, and no additional malt is added, the result would be a beer that is more bitter than intended.

From looking at the Mr. B site, it looks like the newer larger refills can be used alone. So, if two newer refills are used together, the brew should be stronger, but mantain the same OG/IBU balance.

I was going to try to plug the information into Qbrew, but am uncertain about the values with the new Mr. B refills. (as I recall, old cans used to be 1.21 lbs per can as "grain"; and for each can use 1 oz at 5 minutes for hops - don't know if this is still correct)

There was some discussion about the OG to IBU ration in one of the recent BYO issues. (I'll try to find which one.)

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"Crazy Climber" post=320848 said:

Another thing to consider is the "bitterness ratio." BU/GU. IBU/SG. Call it what you want. It's a measure of the beer's perceived bitterness.

You take the IBU and divide by the decimal portion of the OG. In theory. 0.5 is balanced. If you get over 1.0, it's getting bitter. So, a 1.060 beer with 30 IBU is balanced (30/60 = .5), while a 1.060 beer with 60 IBU is bitter (60/60 = 1.0).

That's very helpful. Thanks for this information, it'll definitely help me formulate future batches.

"hi4head" post=320983 said:

First, which cans of St. Patricks are we talking about? Old 1.21 lb cans or the new larger refills.

The new ones.

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I use the IBU/GU formula. The more malt you use the more IBUs you need to balance it out. So IBUs by themselves are not really a good way to gauge how bitter a beer will be. Especially if you do a variety of strengths of beers.

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It just seems appropriate to paste this chart here, as quick visual guide. This is not perfect, nor is the formula itself, because the kinds of malts you use (lots of crystal, dark roasty malts) also can affect perceptions, but it gets you in the ballpark.

Note that a can of the new St. Patricks is 50 IBUs at 1.03something if you brewed it straight up. Which is why I said you have plenty of room to add more malt to it in an LBK sized batch instead of tossing in a second can.

[attachment=10496]hopsgraph.jpg[/attachment]

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You beat me to it (by 8 hours), mashani -- I was going to post that chart because it's basically a graphical representation of the BU/GU ratio I mentioned earlier. Same concept. I like the ratio because it's easy to calculate whether the chart is handy or not.

I occasionally sort my list of past recipes by the bitterness ratio (in BeerSmith, or a spreadsheet) and see how they compare to each other. That gives me an idea of how my tastebuds are likely to perceive a future recipe -- bitter, malty/sweet, balanced, etc. With experience, you can begin to mentallly formulate your own version of that chart, based on your particular perceptions.

And you make a good point regarding how the types of malts used will have an impact on perceived bitterness. Stouts "need" a lot of bitterness just to balance the strong, roasty flavors of the malts, for example.

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