Posts Tagged ‘aa%’

The Circle of Beer…

Sunday, February 26th, 2012

You may notice some cosmetic changes to the website happening, as we streamline and update the format and the look. We don’t plan to change much as far as the content and style go; that all seems to be working pretty well.

One piece I have been asked to do more frequently, though, is tasting notes and reviews. I guess there are some folks out there who respect my taste and opinions about beer and want to know what I’m drinking when I’m not drinking my own homebrew. So OK, I will try to take notes from time to time and post some reviews of recent interesting commercial beers I’ve tasted.

One person who has asked for these reviews is my friend Sarah, wife of webmaster Rick. And coincidentally, she dropped off a beer for me the other day that she had found in a store (not ours) while doing some errands. She and Rick shared 5/6 of a six-pack while waiting for me to get around to tasting my one bottle and giving my two cents. I’ve done one better and actually given them a clone recipe to brew it. Since today would have been Sarah’s late step-father Greg’s birthday, it seems especially appropriate to raise a glass to him, review the beer and publish a recipe to brew your own at home.

Coal Porter, brewed in Bar Harbor, Maine, by Atlantic Brewing Co.

This is a deep reddish-brown to almost black porter, with a thin but resilient tan head. It pours with the impression of thickness (which it really isn’t) and glows in the glass.

The nose reminds me of espresso beans (not necessarily brewed espresso, just the roasted beans), with hints of molasses and burnt sugar. There are some hop notes in the nose (a very English profile, to my senses) but the balance is towards roasted malt and sugars.

The first taste has traces of the same molasses, burnt sugar, perhaps toffee, and roasted malts. I detect a bitterness at the back of the tongue, but not much hop “flavor”. As the beer warms a little, there is more molasses and caramel, perhaps even a hint of praline/pecan. I like the balance between the roasted malt and the sweetness, it might well benefit by just a bit more mid-boil hop flavor.

This is not so much an American-style porter (like, say, Great Lakes Brewing’s Edmund Fitzgerald or the late-lamented Catamount Porter) but more of a mellow, sweet English-style brew, even approaching the sweetness and roastiness (if not the strength and full body) of the Taddy from Samuel Smith’s.

Overall impression: very drinkable sweet porter, not far from an English brown stout in terms of malt profile. If you like hoppy, aggressive American porters, this is probably not going to be your favorite. But if you like a more malt-oriented sweet porter, you will enjoy Coal Porter.

3.9/5

The Recipe:

5 gallons, all-grain

Ingredients:

  • 8 lbs. 2-row pale malt
  • 1/2 lb. 60°L crystal
  • 1/4 lb. dark Munich malt
  • 1/4 lb. chocolate malt
  • 1/4 lb. black malt
  • 8 aau’s* Target (or Magnum) hop pellets
  • 5 aau’s Willamette (or Fuggles) hop pellets
  • English Ale yeast (Danstar Windsor dry yeast, White Labs London Ale yeast)
  • 1 cup amber DME (for priming)

OG: 1050

IBU’s: 37.5

Mash: 60 minutes in 13 quarts water at 152°F.

Sparge: 13 quarts water at 170°F.

Kettle: 60 minute boil, Target hops for 60, Willamette at knock-out.

Pitch yeast at 70°F.

Primary fermentation: 68 – 70°F for eight to ten days.

Secondary fermentation: cool (45 – 50°F) for three weeks.

Bottle condition cold for months (Atlantic claims to cellar theirs for six months before release).

What’s an “aau”? Hops used in a recipe are measure in basically three ways, depending on where you are in the process. The bitterness of a particular batch of hops is indicated as a “percent alpha acid”, or %aa. The higher the number, the more bitter the hop. The number of ounces of a hop used multiplied by its aa rating give the “alpha acid units” value, or aau. For example, 1/2 oz. of a 7% aa hop would give 3.5 aau’s. 2 oz. of a 4.5% aa hop would give 9 aau’s. When the hops are used in the boil, the aau’s are multipled by a utilization factor (ranging from .7 for dry-hops or hops added for less than 5 minutes of boiling; to 4.5 for hops in the boil 90 minutes or longer), a table of  which can be found in our Seven Barrel Brewery Brewers’ Handbook (p. 299). This gives you the approximate IBU (International Bitterness Units) rating. In this recipe, there are 8 aau’s for 60 minutes (factor of 4.25, or 34 ibu’s) plus 5 aau’s at KO (factor of .7, or 3.5 ibu’s), thus 37.5 IBU’s in total.


A Bitter Subject – Hops, aau’s, IBU’s, HBU’s…?

Friday, January 15th, 2010

Caution: technical stuff and math follow!

What do you think when you see a beer recipe that calls for hops measured not in ounces but in HBU’s? or when you read a label and it tells you the beer has so many IBU’s? Ever notice on that packet of hops you bought at the Home Brew Store that the hops are rated based on aa%? What gives? How do you figure out how much to use? It’s not as complicated as it looks at first blush.

AAU’s and aa%: The relative bitterness of a given crop of hops is measured based on the acidity of the flower. The acid that brewers are primarily concerned with is the “alpha acid”, or aa – this is measured in a percentage, hence aa%. The higher the number, the more acidic and thus the more bitter the hop. The Hallertau I used this morning measured 3%, the Perle 6%, so the Perle were twice as bitter as the Hallertau. An AAU (alpha acid unit) is the product of the percentage of bitterness times the amount used – 1 ounce of those 3% Hallertau provides 3 AAU’s, one ounce of the Perle provides 6 AAU’s.

More common and relevant to the homebrewer is the HBU – Homebrewer’s Bitterness Unit – but it’s exactly the same thing as an AAU. If your recipe calls for 6 HBU’s of a given hop, work backwards. If you have a Chinook hop at 12% aa, you need to use 1/2 oz. to get 6 HBU’s (or AAU’s) – right?

IBU’s – International Bitterness Units – are the result of using the hop. There is actually an esoteric table which gives an indication of how bitter a beer will be based on how much of which hops are boiled, and for how long. So IBU’s are the sum total of all the hops added in a given beer, multiplied by a factor depending on length of boil and volume and strength of the wort. For more information on this, I recommend the excellent discussion in Greg Noonan’s “New Brewing Lager Beer”.

In a nutshell, the average homebrewer can use the following simplified tables, which I used in “North American Clonebrews”, although it is based on a table Greg devised for the “Seven Barrel Brewery Brewers’ Handbook”.

Assuming moderate/average strength wort, in a 5-gallon boil:

  • 0 minutes, or dry-hopping – .7
  • 5 minutes – .7
  • 15 minutes – 1.25
  • 20 minutes – 1.5
  • 30 minutes – 2.4
  • 45 minutes – 4.0
  • 60 minutes – 4.25
  • 90 minutes – 4.5

So one would multiply the HBU’s (aa% times ounces) times the above factors, to get the IBU’s.

If one boiled only one ounce of a 4.5% aa hop for 60 minutes, one would have 19.1 IBU’s (4.5 x 4.25)

But if one also boiled one ounce of a 2% aa hop for 5 minutes one would end up with 20.5 IBU’s (add another 1.4, or 2 x .7).

So work backwards – if you know the approximate IBU rating you are shooting for, it is relatively easy to calculate the amount of hops, the desired aa%, and the length of boil. At least I think it is…

Looking at the recipe I posted earlier for the Dortmund Export, we see a total of 22.5 IBU’s. 3.2 of that came from the first addition of Hallertau (.25 x 3 x 4.25); 12 from the 45-minute addition of Perle (.5 x 6 x 4); 5.4 from the second batch of Hallertau (.75 x 3 x 2.4) and the last 1.9 from the final addition of Hallertau (.5 x 3 x 1.25).

So a quick quiz: If you boil 1/2 oz. of Galena at 8% aa for 90 minutes, 1 oz. Tettnang at 4% for 45 minutes, and dry hop with 1 oz. Saaz at 5%, how many IBU’s will the beer have? (Answer follows)

.5 x 8 x 4.5 = 18; 4 x 4 = 16; 5 x .7 = 3.5; total 18 + 16 + 3.5 =37.5 IBU’s.