Alpha Acid Change From Year to Year

[Alphaacid]

How are you compensating for different alpha acid levels from year to year?

Say I brew a pale ale with 50IBU's with X hop at 10%a.a, the following year hop X is 6.5%. How do you adjust your recipe to compensate?

[BDL]

Alpha acid calculator gets you most the way there, then its just tweaking recipes with analytical/sensory feedback.

[MatthewS]

I do this. Not exact but close enough.

11# of Old alpha - 10%
9.16# new alpha - 12%

I take (weight*old alpha)/new alpha
11*10=110/12=9.16#

Kind of simple version of the alpha conversion calculator I think, but it's pretty close and has worked for my purposes.

[dick murton]

For best consistency, you should adjust like this every time the AA changes, which will be most batches of hops. Providing they are not years old hops and have been stored properly, the usable AA value of a particular batch of hops will not change appreciably over 12 / 15 months

[JLL]

This is going off what Matthew said, but when I create a recipe, instead of just having X Hop at Y AA% at Z Pounds, I have "alpha pounds" or "AP" to avoid having to change a recipe everytime the hops change. This also helps when blending in the new hop. Here's an example:

IBU needed: 30
Warrior 16% AA = 3.5 lbs of hops
AP= (AA * Hop Weight) = (16 * 3.5) = 56 Alpha Pounds (AP)

Now let's say we have only 2.5# left of the 16%AA Warrior. Then we need to add more of our new crop, 12%AA Warrior. We still need 56 AP to achieve the required IBU. Here's an example of how to mix different AA hops:

IBU needed: 30
AP needed: 56
(16.0%AA * 2.5#) = 40 AP (We are 16 AP short of our target)

To correct for the missing 16 AP, we will divide the remaining AP needed by the new AA% to determine the amount of new hops needed:
(16AP / 12%AA) = 1.33# of 12%AA Warrior

Math check:
(16%AA * 2.5#) = 40AP
(12%AA * 1.33#) = 16AP +40AP = 56AP

[Swags]

Hop Storage Index

For best consistency, you should adjust like this every time the AA changes, which will be most batches of hops. Providing they are not years old hops and have been stored properly, the usable AA value of a particular batch of hops will not change appreciably over 12 / 15 months

I've seen some hop storage index numbers like 65% AA remaining after 6 months of storage. Is this misinformation? Also, if the AA drops appreciably over time, are the hops still good for dry hopping or does the effectiveness for dry hopping decrease in proportion to the AA?

Thanks for your input!

[dick murton]

Firstly - a bit of a disclaimer in that I have never been quoted such a drop in AA, so these are thoughts rather than based on practical personal experience.

I assume that the hops are not vacuum / nitrogen packed or not stored cold in that case. If properly packed and cold stored I would expect a negligible drop in AA. Actually the bittering potential remains far more constant than the hop aroma. I wouldn't expect the bittering potential / ability to drop as much as the measured AA, but although only a visual / smell inspection will verify, I would expect the hops to be useless for aroma.

I did have the experience of having to use a number of different 5 (ish) year old pelleted hops, but stored at ambient most of the time, not in a cold store. The bittering (i.e. measured IBU at package) was pretty much as calculated from the value stated on the pellet packaging, but the aroma was totally lacking or awful, depending on the hop type. In this particular case, there was no way they were usable for late or dry hopping.

[WWSean]

I do this. Not exact but close enough.

11# of Old alpha - 10%
9.16# new alpha - 12%

I take (weight*old alpha)/new alpha
11*10=110/12=9.16#

Kind of simple version of the alpha conversion calculator I think, but it's pretty close and has worked for my purposes.

I use this method as well and haven't had any issue but also have never had that large of a drop in AA between years.