IBUs - Let's get this sorted out.

It is the Isomorized Alpha Acid in beer that corresponds to IBUs, not the AA. Just to be correct.

 

First, acidity and bitterness are really two fundamentally different things as far as taste is concerned. They are two of the five things your tongue can actually detect (with the others being sweet, salty, and savory/umami). Second, it's possible to measure the pH of something just like you can measure the IBUs, residual sugar, salt content, or glutamate concentration. Those numbers would all from compounds that exist in precise concentration in whatever you are measuring, but to try to quantify the perception of those compounds in a way that would be accurate for everyone (or even a majority of people) would be impossible.

 

Balancing your Beer with the Bitterness Ratio

 

That is one tool. Considering the IBId and Final gravity is often usefull. Two beers with the same IBUs and same OG would cave different perceptions if the FG were different.

 

it's called a tongue preferably your own.

 

High Sulfate levels also give an enhanced sharp and lingering dry finish.

 

Molecules in the hops, called alpha acids, change shape when heated (in a solution), becoming isomerized alpha acids. They cause the bitterness. 1 mg of iso-alpha acid in 1 liter of beer = 1 IBU.

The more IBUs a beer has, the more bitter it is; BUT your ability to taste that bitterness is affected by the sugars in the beer. A higher IBU beer may even taste less bitter than a lower IBU beer, depending on the malt sugars.

 

nope

 

Cohumulone content in the hops being used has a big impact too, regardless of IBUs. Higher Cohumulone hops will be harsher on bitterness than ones with a lower amount of Cohumulone. Reasons I love Magnum and Warrior in home brews for clean bitterness...

 

To expand on jmw's post, we all have unique perceptions based on our genetics and experiences.

Genetics explains why 20%of the population think that cilantro tastes like soap? PTC is a compound that is very bitter most, but 20% do not get any bitterness. Learn some science about taste and genetics here!
http://learn.genetics.utah.edu/content/inheritance/ptc/

There seems to be this misconception that acids are bitter, which is false. Acids give you sour flavors, acetic acids, lactic acid, citric acid, and so on are sour. Alkaloids are often bitter. Isomorized Alpha Acids are bitter. Here is a search result to lay that out.
http://chemse.oxfordjournals.org/content/30/suppl_1/i68.full

 

Actually, its putting a number on a very objective thing -- the amount of isomerized alpha acids. Its as objective as abv.

Just like with ibus, two beers with the same abv may have a different alcohol taste.

 

Prove it.

 

Genetics explains why some have blue eyes and some don't, but there are a small number of eye colors. Hair colors can be grouped into categories. Individual differences do not mean there are no commonalities and reasonable groupings.

 

Read my post above. We are all genetically wired different for taste and aroma. We all have different blind spots. We all have different experiences that make up our taste memory.

Breweries have tasting panels made up of personnel that have mutually exclusive blind spots. You don't want everyone one the panel that decides to package and ship a batch to be blind to Diacetyl.

 

It also explains why some are colorblind, or cannot taste certain compounds like PTC. Please read the link I posted on PTC.

 

I have, long ago.

It clearly states there are groupings, eg PTC is tasted by about 75% of a given population, and that there is variability within populations and groups within populations. But that does not mean that every individual so unique that there are not commonalities or similarities within groupings.

 

I read your post above. If we all had different blind spots there would be no way to assemble a tasting panel without using all of us.

Edit: there are a limited number of blind spots and reasonable groupings of people.

 

OK, I see that your point about commonality groupings in genetics is valid. There are people I know who are hypersensitive to diacetyl and blind to DMS. Another gets both at low levels. Experience is also a big factor. Then there is the connection from the reptile brain to the verbal center, I go, know that taste, my wife will say what it is and I say yes. Her verbal connections are much stronger.

 

Also a good point.

Edit - so that is why we have beer advocate!!!

 

Bingo!