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Old 12-20-2011, 04:21 PM   #21
Bensiff
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The good thing Veedo is that 5.2 is a balance. For some things the ideal range is higher, for some the range lower. 5.2 is just the happy mid-point of balance in these things so if you went a little low you are still good and no one tasting your beer will ever know.

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Old 12-20-2011, 06:07 PM   #22
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A few things to comment on re this thread:
1. The real pH of mash (and most buffer systems) changes with temperature. With mash it shifts down as temperature goes up. The usually stated number of 0.3 between mash and room temperature is higher than what is usually observed. Also "mash temperature" could be the temperature for a beta glucan rest (105 °F), for a protein rest (122 - 128 °F) or a saccharification rest (142 F - 157 °F). Obviously, the shift RE room temperature will depend on which. ATC in a pH meter does not correct for this effect.
2. The response of a pH electrode depends directly on the temperature:
E = E0 + R*T*(pH-pHi)
where T is the tempearture (in Kelvins). It is the job of ATC to compensate for this effect.
3. pHi (the isoelectric pH) is assumed to be 7. If it isn't ATC will lead you astray rather than help you. While larfe error in pHi isn't usual it is safest to measure buffers and sample at as close to the same temperature as possible. As high temperatures stress pH electrodes it is good to have this be close to room temperature.
4. There are lots of opinions as to what the ideal pH range is. Mine is that it is 5.4 - 5.6 at room temperature.
5. Most beers, including some pretty dark ones, will require some form of acid to be added to the mash to get pH into this range.
6. Acid (or alkali) added to mash must be mixed in very thoroughly and some time must be given for it to react before a new pH reading is taken.
7. pH meters can be quirky. With experience you will learn when to be suspicious. If suspicious to a calibration check with 4 and 7 buffers.
8. Three point calibration is not necessary for brewing. pH 4 and pH 7 buffers are plenty. If you are measuring outside 4 < pH < 7 then a 10 buffer calibration point is advisable.
9. Buffers should be freshly prepared. This is especially true of 10 buffer which will pick up CO2 from the air.
10. The pH of distilled water will be less than 7 (also because of pickup of CO2 from the air).
11. The pH of the mash water has little to do with the pH of the mash. The alkalinity and hardness of the mash water do.

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Old 12-20-2011, 06:36 PM   #23
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Quote:
Originally Posted by ajdelange View Post
The usually stated number of 0.3 between mash and room temperature is higher than what is usually observed.
thanks for the replies guys. aj, could you explain this part a little better? i guess from now on i will shoot for 5.4-5.6 at room temp to make it easy. also, do you have any personal experience on when you will begin to tase lactic acid?

one more question, will ph drop in wort that has been boiled, and if so, about how much? if i knew that, i could somewhat confirm where my ph was on the last brew day. i have a sample on the counter that is reading 5.0.
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Old 12-20-2011, 07:32 PM   #24
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Quote:
Originally Posted by Veedo View Post
aj, could you explain this part a little better?
It's probably obvious that the shift is going to depend on the nature of the buffering i.e. how much comes from phosphate, how much from carbonate, how much from which residue on what amino acid, mash thickness and probably the Nile flood stage. I am not willing to sacrifice a pH electrode for a full run from room to mash but I have gone up in temp enough to measure the slope near room temperature. It was about 0.0055 pH per °C. Assuming that the response stays linear at the higher temperatures this would amount to an 0.24 pH shift from room temp to 150 °F and 0.17 from room to 125 °F.

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Originally Posted by Veedo View Post
...do you have any personal experience on when you will begin to tase lactic acid?
I would only tase it if it got totally out of hand (sorry - I just had to). I don't use lactic acid. I use sauermalz. I have never used it at above the 3% of grist level and you do taste it there but it does not taste sour. It, to quote the Weyermann website "adds subtle complexity to the beer" and those are better words than I could come up with. I, obviously, consider this a definite benefit or I wouldn't use the stuff.

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Originally Posted by Veedo View Post
one more question, will ph drop in wort that has been boiled, and if so, about how much? if i knew that, i could somewhat confirm where my ph was on the last brew day. i have a sample on the counter that is reading 5.0.
That again depends on a lot of things. I'd guess that 0.1 - 0.2 would be typical. Some brewers add acid and/or salts to the wort to insure this.
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