I've gotten interested in the equations people have come up with
for computing bittering. If you compare Rager versus Tinseth,
one difference that really stands out is that Tinseth predicts
that you start to get bittering pretty quickly, even when you
haven't been boiling for very long, whereas Rager predicts
that the bittering takes a while to get going. This could have
a big effect on the amount of bittering that you think you're
getting from fini****ng hops that you add 10 or 15 minutes
before the end of the boil.
So here's the experiment I did. I weighed out approximately
0.02 oz of 12% Yakima Galena pellets, and boiled them in a
pint of water. After 20 minutes I poured off 1/3 of this,
and I called this sample S, for "short boil."
Then I kept on boiling the other 2/3 for another 20 minutes,
and after that was done I split it into two equal parts,
which I called R and T for reasons that will be evident in
a moment. I diluted sample R by a factor of 2.4, and T by a
factor of 1.45.
According to the Rager formula, samples R and S should
have the same bitterness, about 15 IBU, while sample T should
be 24 IBU.
According to Tinseth, it's T and S that should be equal, with
32 IBU, and R should be 20 IBU.
Tasting the three samples, I judged R to be much, much lower in
bitterness than S, which is evidence against the Rager formula.
Actually, I even judged T to be less bitter than S, but T and
S were definitely more similar than R and S.
If anyone else wants to try this with some leftover hops,
I'd be interested to see what they think. It only takes about an
hour to do the whole thing, and the amount of hops it uses up is
teeny. (If you want a quick and dirty way to get a reasonable
amount of hops, .02 oz seems to be a line of pellets a little more
than an inch long.) It would also be interesting to try it with
a sugar solution rather than pure water.
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