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 finishing 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.

After I did the original experiment, it occurred to me that
it may not have been a valid test, since utilization is supposed
to be a measure of the amount of the alpha acids that goes into
solution, but my three samples of hops tea all had hops solids
suspended in them. I realized that when I was tasting the samples
I might have been tasting both the dissolved isomerized alpha acids
and the non-isomerized alpha acids in the hops particles.

When I got up this morning I tried the experiment again, but this
time I poured each sample through a coffee filter at the end to
get rid of the solids. This time, I judged the bitterness of the
T and S samples to be equal, but the R sample was still much less
bitter than the S. So in my opinion this experiment supports Tinseth
and is strong evidence against Rager for short boils. The filtering
really made a huge difference. In the original experiment, without
filtering, the S sample was so bitter that it made me feel like
my tongue was being made into shoe leather. It was much less bitter
after filtering.

I decided to do another experiment to see whose bittering formula
seemed to work better when the boil time was held constant, but the
boil gravity was varied. I rigged up a double boiler, and boiled
two samples of wort/hops tea inside it. One sample had nothing but hops
and water, and the other had table sugar that brought its boil
gravity up to 1.086. I used about .07 oz of 12%% alpha
pellets, in a total of 1 quart of water, boiled for 30 min. I also put all
the samples through coffee filters to get rid of hops solids.

Each formula gives a prediction for the ratio of the IBUs of the
gravity-1.000 sample and the IBUs of the 1.086 sample:

Rager .85
Garetz .64
Tinseth .46

I split the sample that was boiled without sugar into three parts,
and diluted each one by the amount that one formula said would give
it the same bitterness as the one that was boiled with sugar.
I added sugar to the unsweetened ones after the boil was over
so they'd have the same sweetness as the one that had had sugar
in the boil.

Ben Crowell lightSPAMandISmatterEVIL.com>:

Scott Sellers wrote:

Yeah, that's a good point. The formulas all assume that you can
break the equation down into two separate factors, one for time and
one for boil gravity. It's possible, however, that that's only
an approximation.

Interesting idea. If anyone following this thread has a brew day
coming up soon, it would be cool if they could draw off samples
at 20 and 40 minutes into the boil and try the dilution and tasting
with real wort.

On Fri, 13 Jun 2008 23:48:23 -0700, lightSPAMandISmatterEVIL.com> wrote:

Keep in mind that boiling hops in water is different than boiling them
in wort. Because the pH of water is a lot higher, you're going to extract
things from the hops that you normally wouldn't in a wort boil. The big
one is tannins, which have a harsh flavor to them that a lot of people
associate with bitterness, even though it's really more of a dry sensation
than an actual flavor. This may be effecting your taste test to some extent.

John.

John 'Shaggy' Kolesar wrote:

On Mon, 16 Jun 2008 08:48:20 -0700, lightSPAMandISmatterEVIL.com> wrote:

John 'Shaggy' Kolesar wrote:

John 'Shaggy' Kolesar wrote:

Not to mention that water alone won't isomerize the alpha acids, so
you're not really geting any bitterness.