IBUs - Let's get this sorted out.

I will post something until someone far more educted happens along.
IBU's measures the calculated alpha acids from the hops...which generally correlate with bitterness. More alpha acids, more bitterness. But, it also depends on the beer style. A stout can have 90 ibu's, but not be bitter at all, because the malt overpowers it. An ipa with 90 ibu's will be more bitter

 

IBU's measure the measurable bitterness. That does'nt mean the same thing t everyone You might think that a bitterness off 75 is egregious, I might think 100 is acceptable. Try thebeer. BUY a single. I think that ultimately the idea that bitterness is masked by other flavors is true so try the beer.

 

I'm often asked what IBU stands for, and feel bad giving the answer. "International Bitterness Units" doesn't really tell you all that much about what that number on your bottle really means, does it? IBUs, when you get down to it, are simply a measure in parts per million of the isomerized alpha acid content in beer. Oh jeez, this isn't getting any easier. To make it short and sweet: IBUs are a measure of how hoppy a beer is.

But that doesn't tell the whole story. Perceived bitterness depends on way more than just how many hops are thrown into the kettle. The sweetness and alcohol level of a beer, for example, plays a huge role in the end bitterness of that beer. Two beers, both with 35 IBUs, can taste bracingly bitter or not at all. So really "International Bitterness Units" is a bit of a misnomer. In fact, as a measure, it is nowhere near as useful as folks to seem to make it out to be, so don't get too caught up on the IBU number.

So... what Jane said... you can only get a general idea of the bitterness by this number alone.

(I wanted to know myself... so I looked it up. This is an excerpt from this article; http://drinks.seriouseats.com/2013/...d-mean-dry-hopped-imperial-what-are-ibus.html)

 

I'd guess that your body has just expanded its lupulin threshold Like you, I can feel the tongue-clenching bitterness, but it is a sensation I look forward to and enjoy in pales. The main flavors I taste are dank, citrusy, floral candy-like flavors.

Like others, I wouldn't necessarily say "higher IBU= slower sipper", and probably closer to the opposite with many. I find that the higher IBU stouts and American barleywines are generally more quaffable to me, the bitterness seems to just add more-ishness.

Not sure if anyone else has said it either, but IBU is a measure of how much lupulin (bitterness compound in hops) the beer has absorbed. Another thing I feel worth mentioning is that while many beers are listed "90 IBU" based on the recipe, the actual IBU is almost always a little lower if they test it with fancy machines. I recall an anecdote by someone from a brewing lecture that Sierra Nevada's Hoptimum has been the only beer to actually test at 100 IBU. Cheers

 

If IBUs aren't a good indication of bitterness then someone should come up with a new method of measuring bitterness that gives the drinker a good idea of what to expect.

 

Can't be done in any practical way. Too many variables influence perceived bitterness, including the distribution, number and type of tastebuds you have. And that is gradually changing such that about 7 years from now you'll have a whole different set than you have now.

 

Yes, that's correct. The bitterness from malts or additives like coffee don't figure into the calculated IBU, only AA from the hops.

 

Right. Two different sources of bitterness. IBU measures only Alpha acids, as markdrinksbeer points out.

 

I've never considered IBU's one time when deciding to drink a beer or not. Nor I have ever wondered how many IBU's a beer is or asked the question of anyone. I simply don't give a shit. It seems to try to put an exact number on a subjective thing. It's just weird to me.

 

Still perhaps there is a way to measure excluding these factors. For example acidity is measured on a scale, can be given a number, and is related to bitterness. I guess perception is really a big factor, but you have to figure that most humans perceive tastes in the same basic ways, except for you super tasters out there...

 

It's all relative to the recipe. A beer drinker who understands gravity, SRM (color), and IBU's can reasonably estimate how the beer is going to taste based on those three measurements. A brewer can plug a recipe into a computer and calculate those same measurements before a beer is even brewed. Gravity (especially the ratio of OG:FG) will tell you abv, or how much sugar has been converted to alcohol and how much remains in the beer. SRM will tell you the types of malts used to get that sugar (and also give a sense of how the different malts will taste). IBU's will give you some sense of the hop bill. But IBU's are useless without knowing the gravity and SRM.

So, if you have a low OG/low SRM beer with 15 IBU's, it still might taste pretty bitter.
If you have a high OG/high SRM beer with 15 IBU's, you probably won't perceive any bitterness at all.

That's a pretty extreme example. I like to use Black Husky Pale Ale as an example (and not only because it's my favorite Wisconsin beer). It's a pale ale, with an ABV of 7.2% (this is a simpler way of telling us that this beer has a medium-high OG/FG ratio), SRM of 6 (golden but not yellow) and 43 IBU's. At first glance, if I told you this was practically an IPA, you'd say, "43 IBU's? That doesn't seem like enough." But, for a Pale Ale to get to 7.2%, you know that the yeast has to have eaten through a ton of the sugars in the beer. That means that the beer isn't nearly as sweet as it would be if it were only allowed to get to 6%. Eating up that extra sugar allows the 43 IBU's to shine through the remaining sugar in this beer. It's still slightly sweet, but any less so and the simcoe hops would get over-powering.

 

There is no reasonable way to measure actual perceived bitterness any more than there is a way to measure the other four flavors (there are actually said to be five flavors @Hop-Droppen-Roll : bitter, sour, salty, sweet, and umami, which is generally regarded as "savory"). The best you can do is measure something that can be objectively quantified--i.e., something that purportedly creates the flavor. Alpha acids for bitterness (which as noted, ignores the bitterness that can come from roasted/charred malts), sugar for sweetness, etc.

The reason being that when the five flavors interplay, they impact how the others are perceived. Sweetness can take the bit off of sourness, and saltiness can enhance the presence of other flavors. It's too delicate an interplay to reasonably measure, so for me, IBUs are mostly a worthless measure. They'd do better to call it something like AAUs (alpha acid units) or some other kind of name that directly correlates to what it actually measures.

 

Amount of Alpha Acid is not subjective and it can be given an exact value. Perceived bitterness, which is personal, can be quantified as well but it's too much work to be worth most people's time.

 

Big difference in calculated bitterness and perceived bitterness, and the difference is the malt. Session IPA's IMO and to my palate are horribly unbalanced and offensively bitter in the most extreme cases. Not a clue what the IBU's are, but it's essentially hop juice. DIPA's don't pack the bitter zing most IPA's do because of the malt which softens the bitter and ups the ABV. I'm not a scientific beer guy I'm sure an experienced brewer or home brewer could give you a more sound answer. I've had 100 IBU brews that were nicely hoppy and some 75 IBU brews which tasted far more bitter, I think the hop styles account towards perceptions.

 

The type of hop needs to be taken into account as well. You could use some "softer" hops and end up with a beer that has XX IBUs. Using the same malt and yeast, but different, more "strong" hops, your IBU number may be lower, but perceived bitterness will be greater. All in all, I find the IBU number to be mostly unimportant. YMMV.