AAU of hop extract

[GRBC]

Hoping the hive can help me figure out the alpha acid unit calculations of hop extract. I received in the mail today my 100 gram tin of CO2 hop extract from Yakima Valley Hops. On the label it says 61 alpha acid.

Now, I have read from Scotland/bertus brewery (http://www.bertusbrewery.com/2012/12/ipa-clone-series-pliny-elder.html) that the hop shot bittering sheet from NB is unreliable, and he figures that each of his homemade 5ml syringes contains 10aau, or 2 AAU per ml of extract. In other words a 5 ml syringe is the equivalent of one ounce of a 10 alpha acid % hop.

So here's my math:

I assume that the weight of the extract is close to the same as water (1 ml = 1 g). Kai seems to support that assumption (http://braukaiser.com/blog/blog/2012/09/09/hops-from-a-can/).

So my 100 gram tin should yield about 20 syringes, each containing 5ml or 5g of hop extract.

100 grams is 3.5 ounces of hop extract. At 61% alpha acids, that is 213.5 total AAUs per 3.5 ounce (100g) tin, or approximately 2 AAU per gram or ml which is around 10 AAU per 5ml syringe.

For now I'm not going to worry about how those AAU from extract relate to a similar value of AAU from hop pellets in terms of IBU (utilization). Any corrections/improvements are appreciated!

 

[Roadie]

I'm more concerned with IBU instead of AAU. Pretty sure I got more than 20 syringes out of my can after warming it up. Just started using mine so no first hand experience yet.


Almost Famous Brewing Company

 

[AlCophile]

I use EtOH(ethyl alcohol) for hop Xtrn., and I suggest you store your extract under an inert gas atmosphere. I also keep my extract cold, but since you have no EtOH present, yours might get cloudy or precipitate out. Try freezing a small amount. Good luck.

 

[GRBC]

I'm more concerned with IBU instead of AAU.


Almost Famous Brewing Company

Yeah, me too - sort of. Except that I plan on using the hop extract primarily for the highly hopped beers like PtE where the calculated IBU don't really end up being the actual IBU in the finished beer. For those beers, I want to avoid boiling 5+ ounces of hops for 90 minutes.

Also, the NB HopShot IBU calculations seem to assume isomerization (utilization) that is about 40% higher than what you calculate from a similar amount of AAU from pellet hops. To illustrate this, I look at the NB cheat sheet (http://www.northernbrewer.com/documentation/hopshot.pdf) where it says that 5ml of HopShot will result in 50 IBU in a 1.050 wort after a 60 minute boil. We have already established that 5ml is 10 AAU. If you calculate the IBU using Tinseth of 10 AAU, or 1 oz of a 10% Alpha acid hop boiled for 60 minutes in a 1.050 wort, you get 35 IBU.