Alpha Acid Question

I am brewing the holly holiday brew from the recipe section. My question is in regards to the AA of the centennial hops. The recipe states centennial hops with an AA of 9.4% and the ones I bought are at 10.3%. Do I just use the entire 2oz or do I adjust? I know it really comes down to taste but will the higher AA make it too bitter?

 

What I do here is some cross multiplication. For instance, if your recipe calls for 2 oz:

Recipe = Current Ingredients

(Qty of Recipe)(AA of Recipe) = (Qty Used)(AA Used)
(2oz)(9.4AA) = (x)(10.3AA)
x = 1.825oz

Use 1.83 oz

 

If you think you can discern a ~9% difference in bitterness...

Cheers!

 

At what point in the process are you adding the 2oz of centennial? If it's at 60 mins then adjust the amount if it is a late hop then leave it at 2 oz. late hops are more about extracting oils than isomerizing alpha acids.

 

Can you post the hopping schedule? It will help determine how you should adjust things. You'll want to change the bittering addition, but by how much depends on when and how much you're adding all the other hops.

 

Sorry I should have added the hop schedule. It was 1 oz 60min then .5oz at 30min and .5oz at 5 min.

This was my first all grain and I added an extra lb of 2 row so I just kept the amount of hops in the recipe. My OG was 1.084 so I guess I did pretty well with my efficiency using batch sparging. Recipe said 1.077 and with the extra grain put it up to 84.

If I may shift the thread to the protein coagulation. There was quite a bit of it. I skimmed a lot but not all. Is that normal?

 

There will be little or no hot break with an extract brew but there will be noticeable amounts with all grain especially on a high gravity brew.

From what I understand all pros will skim off the break material but they're dealing with much larger amounts than us. Getting any proteins out of your beer is always a good thing. Pros are more concerned about it as proteins will shorten shelf life. Not as big as a concern for us but worth the few seconds it takes to skim the hot break.

 

Perhaps a ~9% differences would go unnoticeable but you may as well learn a strategy for when your recipe calls for 4.7AA hops and your LHBS only has 8.5% and you're suddenly faced with an 80% difference.

 

Back to the hops for a moment...

I ran your numbers (roughly) through BeerSmith. At an AA% of 9.4% your beer would have had an estimated 57.4 IBUs. Using the higher AA% of 10.3%, you have an estimated 62.9 IBUs...so, really not much of a difference. (I used the Rager method for estimating IBUs).

As for skimming the protein...most all-grain beers should have a good amount of protein from the hot break. I never skim it and haven't any problems as far as I can tell.

 

As a practical matter, it won't make much of a difference in this recipe.

For future use though, lots of recipes will list 60 minute additions in bittering units instead of ounces. (Bittering units) = (ounces of hops) x (AA% of hops) eg 2 oz of 5.2 AA hops would be 2x5.2=10.4 bittering units. Your recipe calls for 1oz of 9.4AA or 9.4 bittering units. To get to the needed ouces of a different AA hop, you divide (9.4 bittering units) by the (AA of your hop) or 9.4/10.2 = 0.92 ounces.

 

LOL! Actually, that'd be time for a whole new recipe as it's unlikely those are anywhere near the same type of hops!

Cheers!

 

Got it! If a recipe states a hop with a certain AA just figure out the hbu and adjust for a hop of differing AA. My only problem is why use .92oz then have to store .08oz. Perhaps use the .08 in addition to the .5oz at the 30 min mark. But then again why complicate things.
Thanks for the replies.

 

Got it! If a recipe states a hop with a certain AA just figure out the hbu and adjust for a hop of differing AA. My only problem is why use .92oz then have to store .08oz. Perhaps use the .08 in addition to the .5oz at the 30 min mark. But then again why complicate things.
Thanks for the replies.

 

For this recipe with this particular hop substitution, you are right to question the need to complicate things - the difference is minimal and probably unnoticeable. However, there may come a time when you will want to make the adjustment.

The big thing to remember is the potential need to adjust the bittering addition and not the later additions...and to keep in mind that some alter additions may impact the IBUs...so you'll need to adjust your bittering addition a second time to account for that.