Hop AA% Testing Theory

I don't grow hops, but as an amatuer chemist that follows this board quite a bit, I see a lot of people asking for how to test homegrown hop's alpha acids. It hit me today that one could get a rough estimate from testing the pH of the hop and comparing it to a previously made chart.

If there are acids in the hops, and by nature acids are acidic, and below 7 on the pH scale, you could test the levels of acids. Granted, you couldn't tell the difference between alpha and beta acids.

I might work on this once I get power back in my basement lab if people think this may work. I'd need to compile a chart of different hop varities's pH based on their acid levels.

If you find a cheap easy way with decent accuracy, you will have everyone's attention I'll bet.
One problem you might have is getting a baseline since I don't know how accurate the label on any test hops would be since they sample crops, not individual plants when they rate them.

Since the alpha and beta acids are not strong acids, pH of the aqueous solution will not give a simple representation of the acids present. If you want to play around with the pKa's of the alpha- and beta-acids in solution here is a link. I think you will agree that resulting pH will not be any kind of determinant of aa% of the hops used.

http://books.google.ca/books?id=zV9bpyykNtMC&pg=PA263&lpg=PA263&dq=pka+humulone&source=bl&ots=FhctI9vmIa&sig=bCxJpZEkiO_EZtoXBCoBlWx1ppw&hl=en&sa=X&ei=CJ2UUIm6D8euiQL72IDQDQ&ved=0CCAQ6AEwAA#v=onepage&q=pka%20humulone&f=false

Thanks. What's most interesting about that section is on page 263, there's a very interesting chart on alpha and beta acids solubility. Perhaps that's the way to go about it.

I'd love to produce a really cheap kit or procedure for home hop growers to approximate their AA%.

The standard way for homebrewers to approximate the aa of homegrown hops is to make a tea with a known amount of commercial hops, and also one with the same amount of homegrown.
Comparing the strength of the two teas by drinking dilutions of each will let you appoximate the aa of your hops.

theredben said:

The standard way for homebrewers to approximate the aa of homegrown hops is to make a tea with a known amount of commercial hops, and also one with the same amount of homegrown.
Comparing the strength of the two teas by drinking dilutions of each will let you appoximate the aa of your hops.

Click to expand...

:facepalm:

I know that's the popular way, I'm talking about something vaguely interesting.

Excuxe my ignorance on the subject at hand but would the aa% not be the same as the mother plants? They should be genetically identical considering they are from the same plant. I was looking into buying a hop plant cutting from my local homebrew shop and they assured me that it was from the same plants the hops that i buy from them grew out of

huntingohio said:

Excuxe my ignorance on the subject at hand but would the aa% not be the same as the mother plants? They should be genetically identical considering they are from the same plant. I was looking into buying a hop plant cutting from my local homebrew shop and they assured me that it was from the same plants the hops that i buy from them grew out of

Click to expand...

Growing conditions will impact aa%. I imagine age of hop plant will as well.

Assuming that they are picked at the peak, the aa% would be similar to the "standard" but the growing conditions throughout the year will also impact the final number.

In other words, you can't take a cascade and turn it into an alpha monster through special care but you can take a Magnum and abuse it sufficiently to drop its alpha way down.