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Old 02-13-2013, 03:29 PM   #1
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Default Witbier chemistry questions

Hey all. I'm going to brew a traditional witbier soon, but I had a few problems trying to sort out the water chemistry and estimating the pH.

The grain bill is simple; 5lbs pilsen, 4 lbs flaked wheat, 1lb flaked oats. Since there's a high amount of unmalted grain in the bill, my mash schedule was going to be 20 mins @ 120F for a protein rest, ~60 mins @ 152 for conversion, and ~10 minutes at 170 for mash out. With a high percentage of pilsen, I was going to boil for 90 minutes. This recipe is all BIAB, so all water will be added at the beginning of mashing. The total amount needed to end with 5.25gal of wort at the end of boil I'm calculating out to be 8.65 gal.

My water report looks like this:

Code:
Calcium (Ca)	9.0	19.0	Bicarbonate (HCO3)
Magnesium (Mg)	1.0	0.0	Carbonate (CO3)
Sodium (Na)	6.0	9.0	Sulfate (SO4)
Potassium (K)	2.0	7.0	Chloride (Cl)
Iron (Fe)	0.0	0.9	Nitrate (NO3)
Still with me? Ok, now here are my questions:
  • I'm calculating Mash Acidification with the flaked grains being classified as base malts under grain type. Is that correct?
  • Will the protein rest have any effect on lowering the pH that Bru'n Water can't/isn't calculating for?
  • Based on my water chemistry and mash volume, I'm estimating on adding 4 g of gypsum and 3.5 g of CaCl2. That seems to give me a decent amount of calcium and gets my SO4/Cl ratio in the same neighborhood of a Hoegaarden profile. Seem sane so far?
  • If I'm doing everything correctly so far, my estimated pH is 5.6 which seems a bit too high. Granted, I know this is just an estimation and I'll need to test, but I like to be prepared. So to get me to 5.4, it looks like I'll need to add 2mL of lactic acid (88%). Sane?
  • Here's where my mind starts to melt down a bit. Adding the lactic drops my RA to -68 and alkalinity to -21. As I understand it, alkalinity is the measure of resistance to pH change. I get that if it's 0, you have no buffering capacity. What does it mean when it's negative? Are those parameters out of line? What effect will negative RA and alkalinity have on the final beer?

Thank you in advance!
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Old 02-13-2013, 04:05 PM   #2
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I wouldn't use gypsum in a witbier. You don't want the sulfate. Use caCl2 to get to 50 ppm+ of calcium or thereabouts.

Use the lactic acid to get to 5.4-5.6 at room temperature.

Don't worry about RA, just make sure your mash pH is in the range (at room temperature) and you'll be fine.

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Old 02-13-2013, 04:09 PM   #3
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Originally Posted by uberg33k View Post
[*]Here's where my mind starts to melt down a bit. Adding the lactic drops my RA to -68 and alkalinity to -21. As I understand it, alkalinity is the measure of resistance to pH change. I get that if it's 0, you have no buffering capacity. What does it mean when it's negative? Are those parameters out of line? What effect will negative RA and alkalinity have on the final beer?
Negative alkalinity means that you actually have to add a strong base (i.e neutralize acid) to get to the alkalinity titration point which is usually a pH of 4.3

This is expected if you add more acid than it takes to neutralize the water's alkalinity. Negative residual alkalinity also means that your water + treatment will lower the mash pH. This is what you want.

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Old 02-13-2013, 04:42 PM   #4
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I wouldn't use gypsum in a witbier. You don't want the sulfate. Use caCl2 to get to 50 ppm+ of calcium or thereabouts.

Use the lactic acid to get to 5.4-5.6 at room temperature.

Don't worry about RA, just make sure your mash pH is in the range (at room temperature) and you'll be fine.
This is what I thought at first! However, looking at Hoegaarden, the SO4/Cl is about 1.5 and Celis White is about 1.1. I can't make any sense of why unless SO4 boosts the flavor perception of the oils from orange peel, corriander, etc. like it does the perception of hops bitterness. Does anyone know for certain?


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Originally Posted by Kaiser View Post
Negative alkalinity means that you actually have to add a strong base (i.e neutralize acid) to get to the alkalinity titration point which is usually a pH of 4.3

This is expected if you add more acid than it takes to neutralize the water's alkalinity. Negative residual alkalinity also means that your water + treatment will lower the mash pH. This is what you want.

Kai
Ok. I think I get it, but I'm going to have to change the analogy in my head. Up till this point, I was thinking of alkalinity as analogous to friction in the sense of classical mechanics. Guess that's out the window now.
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Old 02-13-2013, 04:47 PM   #5
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If you are looking for useful analogies, take a look at this: http://braukaiser.com/wiki/index.php...for_pH_Buffers

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Old 02-13-2013, 04:53 PM   #6
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This is what I thought at first! However, looking at Hoegaarden, the SO4/Cl is about 1.5 and Celis White is about 1.1. I can't make any sense of why unless SO4 boosts the flavor perception of the oils from orange peel, corriander, etc. like it does the perception of hops bitterness. Does anyone know for certain?
What is the source of that information?
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Old 02-13-2013, 05:01 PM   #7
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What is the source of that information?
Bru'n Water has a profile for Hoegaarden built in.

I'm basing the Celis White profile on an old Austin,TX water report I found online.
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Old 02-13-2013, 06:49 PM   #8
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Up till this point, I was thinking of alkalinity as analogous to friction in the sense of classical mechanics. Guess that's out the window now.
If you can do EE-speak (and as you mention the mechanics analog I'll bet you can). pH is like voltage (it is in fact a potential - the chemical potential of hydrogen ions) and solutions are like capacitors. If yoy have a capacitor charged to x volts and you connect it in parallel to another capacitor charged to y volts current will flow until the two are at the same voltage. The voltage and the amount of current that flow depend on the voltage difference and the sizes of the two capacitors. Alkalinity is akin to the capacitance. If the target capacitor is large a lot of current has to flow to bring about a desired voltage change. Similarly if water has high alkalinity a lot of protons have to flow.

As with an electrical circuit there is a reference pH which defines all this. WRT alkalinity it is 4.3 or 4.5 or some number close to that. Just as you can charge a capacitor to negative voltage (less than the reference of 0) you can protonate a system to less than the reference pH.
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Old 02-13-2013, 07:16 PM   #9
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If you can do EE-speak (and as you mention the mechanics analog I'll bet you can). pH is like voltage (it is in fact a potential - the chemical potential of hydrogen ions) and solutions are like capacitors. If yoy have a capacitor charged to x volts and you connect it in parallel to another capacitor charged to y volts current will flow until the two are at the same voltage. The voltage and the amount of current that flow depend on the voltage difference and the sizes of the two capacitors. Alkalinity is akin to the capacitance. If the target capacitor is large a lot of current has to flow to bring about a desired voltage change. Similarly if water has high alkalinity a lot of protons have to flow.

As with an electrical circuit there is a reference pH which defines all this. WRT alkalinity it is 4.3 or 4.5 or some number close to that. Just as you can charge a capacitor to negative voltage (less than the reference of 0) you can protonate a system to less than the reference pH.
OH!!!

Yeah that makes sense now!

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Old 02-13-2013, 08:05 PM   #10
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For my Wit, the SO4/Cl ratio was 1.6
My profile looked like this:
Ca-52, Mg-20, Na-11, SO4-135, Cl-80, HCO3-147

I did acidify the mash with 25% Phosphoric Acid

Loved the beer and will brew it again.

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