FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
Questions - I ("A.J deLange")
Questions II ("A.J deLange")
Re: pH stuff (Kai Troester)
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Date: Fri, 03 Oct 2008 10:46:24 -0400
From: "A.J deLange" <ajdel at cox.net>
Subject: Questions - I
Lots of questions - almost like the old days.
1: Are my postings too heavy for this forum? Yes and no I think. Yes,
they will be over the heads of some, a small fraction of whom will
resolve that some day they will not be over their heads. Those are the
ones I am after. They are the ones that will eventually get the most out
of HBD. OTOH there are some here who are familiar with these concepts
and techniques because they work (or have worked) in the sciences or a
related field or are students in some related field. For them these
posts should not be over the top.
E0 is the reference potential of a pH electrode i.e. the voltage it
produces under a standard set of conditions. The goal for a modern pH
electrode is that it produce 0 mV in a pH 7 solution at 20C. None do
exactly this and that is one of the reasons a calibration with buffers
must be done. R is the universal gas constant and F is the Faraday
constant. RT/F (T is temperature in Kelvins) is the "slope" of
electrode which should be about 57 mV per unit of pH at room
temperatures (but, again, it never is exactly which is the other reason
for calibration).
2: How far off is the Brix/Balling/Plato scale given that it is based
on sucrose and wort isn't? I don't really know the answer to that
because the sugar spectra of worts differ dramatically and it is very
difficult to get Plato-type data on other sugars. Anyone who has opened
a package of DME on a humid day will understand why (it picks up water
very fast becoming a gooey mess which would be very difficult to weigh).
This is why sucrose was chosen - it can be handled relatively easily.
Another thing to keep in mind is that what we have here is a standard
i.e. the absolute accuracy is not so important as that everyone get the
same numbers under identical conditions which allows interfacility,
inter brew etc. comparison. I often site the FAA's practice of making
everyone set his altimeter to 29.92 above 18,000 feet. No one is
actually flying at the altitude indicated by his altimeter but everyone
whose altimeter reads 30,000 feet is at the same altitude (which is very
probably not 30,000 feet) and that's what counts. Nonetheless in every
experiment I have done with other sugars (including some dextrines and
even starches) the agreement to sucrose is surprisingly close.
3. "How does one get a mash sample down to room temp is a reasonable
length of time...?" I dip it into a tiny saucepan (holds perhaps half a
cup) which I swiped from my wife's kitchen. This I lower into a sink
with an inch or two of cold water in it and let it sit for a few minutes
stirring it from time to time. I don't always wait until it hits exactly
20 C but alway record the temperature at which the pH measurement was
actually made.
4. "Should I build water from the ground up...?" This is a philosophical
question which has been discussed endlessly. When I first joined HBD
years ago it was a hot topic with ion profiles for various cities and
recipies for formulating them being posted frequently. One thing to
think about is the case where you decide to brew a Munich Helles with
genuine Munich water and so go to considerable trouble to get carbonate
to dissolve (next question) only to have to remove it when you soften
the water as required for a Helles. Why put it in in the first place?
Many situations are like this. The trend these days seems to be to get
the mash pH in the right region and add salts which are not related to
mash pH shift to taste.
5. How much pH shift before the effects of it are noticeable in the
beer? Only you can answer that question. Proper mash pH is required for
most efficient enzyme utilization. This may be important to a commercial
brewer for whom a percent or 2 difference in mash efficicency translates
into railroad cars of malt over a relatively short period of time but
for a homebrewer it is a matter of a couple of dollars more or less. Who
says that a beer from a less efficient mash may not be a better tasting
beer? Experiment!
6. "How should I convince the minerals that they should stay in
solution?" Getting them to dissolve is the first problem and the way to
solve it is to use acid. This can be in the form of a mineral
(hyrochloric or sulfuric) acid but I do not recommend those as they are
potentially dangerous and getting them in food grade is likely to be
difficult. That leaves carbonic acid, i.e. bubble (use a carbonating
stone or airstone) CO2 through the water after you have suspended the
salts. This takes a long time and a lot of CO2. If the salts want to
come out of solution in the hot liquor tank (a likely place) they will
but they probably did that at the brewery in Munich too. Again, why put
them in in these cases?
... continued in next post
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Date: Fri, 03 Oct 2008 10:47:28 -0400
From: "A.J deLange" <ajdel at cox.net>
Subject: Questions II
7. "...when should I end my sparge?" The usual wisdom is to terminate
when the pH approaches 6 and that's probably as good a way as any to
determine when to quit. If you've done things right the gravity of the
runoff should be 2 - 4 P at this point. Think about what 4 P means. A
liter of runoff weighs about a killogram 4% of which (40 grams - an Oz
and a bit) is sugar. Do you want to risk husk tannin extraction for that
amount of sugar? I have found by experience with my system that the
kettle is about full when the runoff hits about 3 P with the pH below 6
so my criterion is to stop collection when the kettle is full to a given
level. I still do gravity (with a hydrometer) and pH checks though.
8. Therminator: Plate chillers are FM. The downside is that you can't
look inside them to see if they are clean unless you take them apart and
you can't take a Therminator apart. Go to Blickman Engineering's website
for data on performance (i.e. how much you can chill how fast at what
cooling water requirement). I think you will find the unit more than
adequate for most homebrewing applications (well beyond 5 gal batches).
9. "Why does ProMash provide a calibration adjustment that recommends a
4% difference between Brix and Plato?" I am puzzled by this too. To get
a handle on what the practical differences between the scales may be I
made a 10% (i.e. 10 Brix, 10 Plato) sucrose solution (tare beaker with
stirbar, add 5 grams sucrose, add water to 50 grams, stir) and
programmed my density meter to read both Brix and Plato. To my surprise
the meter indicated 10.00 Brix and 10.00 Plato. The surprise was not
that they read the same - I expected that- but that I was able to hit
the target spot on. As a further check I consulted the ASBC tables which
indicate specific gravity for 10.000 Plato of 1.04003 and that's exactly
what the meter read.
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Date: Fri, 03 Oct 2008 12:41:28 -0400
From: Kai Troester <kai at braukaiser.com>
Subject: Re: pH stuff
> Ok I have allot of questions about technique. How does one get a mash
> sample down to room temp in a reasonable amount of time in order to
> make salt/acid additions?
I used to use a large stainless steel bowl to cool down a small
sample. Now I just keep a small dish in the freezer and take it out
when I need to cool a sample
> Because I use R.O. water should I be building water from the ground up
> based on the brewing region of the style in preperation for brewing instead
> of adding minerals to the boil kettle?
Build your water before adding it to the mash. But don't get to hung
up on the regional water profiles. Many breweries treat the water and
as a result of that don't use the water profile that is reported for
that region. When I build water I pay attention to these parameters:
Calcium should be above 50 ppm
Residual alkalinity (balance between Alkalinity and Ca/Mg) should
match the color of the beer that is brewed.
Sulphates should be low or high depending on the desire to emphazise
hops or not.
John Palmer's How To Brew has a nice table about the desired levels of
various minerals.
I add the salts to the water. Chalk doesn't readily dissolve, but it
stays in suspension long enough that it is not left behind in the pot
when I add the water to the mash. If you get the residual alkalinity
right, you should not have to adjust the mash but it is always a good
idea to check the pH. If adjustments are necessary add chalk or acid
(I like to use acid malt). And note that so you can do that ahead of
time next time you brew that recipe.
Kai
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End of HOMEBREW Digest #5427, 10/03/08
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