5.2 and CO2 Off Flavor

[Nyakavt]

Yes, standard.

So that means that the pH at mash temp should be 0.35 lower (supposedly) than the measured pH at room temp.

According to the research Kai has done, the commonly accepted mash pH optima (as measured at room temperature) is 5.2-5.5, and it is thought that it is better to be on the low side of that range. There guys are getting readings above 5.6 with this 5.2 stuff, so it is a poorly suited to moving the mash into the commonly accepted optima for both flavor and enzymatic activity. IMO that's reason enough to use something else. It also doesn't do as advertised: no matter if you measure the pH and room temp or mash temp, you will not get to 5.2 with this stuff according to TB's and AJ's experiments. It gets even worse when you use water with even a small amount of alkalinity.

http://braukaiser.com/wiki/index.php/Ho ... c_activity

yep @ room temp - so liquid with the same pH measured at mash temp would read, as you said, about 0.3ish lower. This is why the pH of 5.2 is used for homebrewers... usually you are talking about someone who is dunking a strip into a hot wort. In that situation, you want to see the strip read 5.2. Whereas the actual pH range, measured at the "calibration temp" of most papers and meters, that you want for a mash is actualy 5.4-5.6.

But pH papers also have a color shift associated with increased temperature (see table below from EDM chemicals, some indicators are higher, some are lower), in addition to a systematic error that causes them to always read 0.3 units low (at least for the colorpHast strips). So a pH of 5.5 as measured at room temp would be more like 5.2 on the strips. And because of the color shift with temperature some strips would read the same at mash or room temperature since the temperature error counters the shift in mash pH. Since this is an unknown, its always best to read at room temperature.

Code: Select all

Indicator     18°C (64°F) pH   100°C (212°F) pH
Methyl violet   0.1 – 2.7      0.5 – 1.7
Methyl yellow   2.4 – 4.0      1.9 – 2.9
Methyl orange   3.2 – 4.4      2.5 – 3.7
Methyl red      4.2 – 6.6      4.0 – 6.0
4-Nitrophenol   5.0 – 7.0      5.0 – 6.5
Phenol red      6.8 – 8.4      7.3 – 8.3
Cresol red      7.2 – 8.8      7.6 – 8.8
Phenolphthalein 8.3 – 10.0     8.1 – 9.0
Thymolphthalein 9.3 – 10.5     8.7 – 9.5

[ajdelange]

De Clerck has some data on this. The slope with temperature appears to be 0.00714 pH/°C for a distilled water mash and 0.00768 for a "medium hard" water mash. Thus is going from dough in at a protein rest temperature *125 °F) to room temperature of 21 °C you might expect a shift of 0.23 whereas going to room temp from mashout temperature these data indicate it could be as much as 0.41. In the days before I knew better I used to measure at mash temperature and when I became aware that most measurements are made at room temperature I started taking note of the difference. They were appreciably smaller (perhaps half) of what the DeClerck data suggest.

[Thirsty Boy]

I think its the German's fault - half the stuff that gets written about brewing is written by/about/for German lager brewing. And those buggers mash in at room temperature, spend the whole morning doing a series of outlandish decoctions, then invade Poland after lunch - so they just take a damn pH reading after they mash in and no need for worrying about temperature or correction.

Screw them I say!!

Calibrated pH meter at 20°C - then you know for sure.


PS - a significant portion of my genetic material is of German origin... so I am allowed to insult the buggers because I'm kinda one of them.

[mlaw06]

Well I have now brewed 11 batches (including the Amber again) since the metallic shit beer. I did not add 5.2 to any of them, and the flavor never came back. The 5.2 was the only portion of my process that was altered. So take it for what it's worth, but I believe the 5.2 was the culprit.

[Pharmbrewer]

Well I have now brewed 11 batches (including the Amber again) since the metallic shit beer. I did not add 5.2 to any of them, and the flavor never came back. The 5.2 was the only portion of my process that was altered. So take it for what it's worth, but I believe the 5.2 was the culprit.

So you did not pay any more attention to rinsing out your pbw?

I'm having a similar metallic taste problem with my dubble I just brewed. (no 5.2) I am thinking it may be the pbw. I have a bottle that I conditioned (never touched the keg) that I plan on comparing, however the bottle did get a secondary fermentation with wine yeast so the comparison won't be completely equal. I'm pretty sure I will still be able to pick up the flavor. I'm actually hoping that this is the problem otherwise I'm at a loss I had perfect temp control piched an appropriate amount of yeast (dry properly rehydrated) I hate the fact that I can't figure out what went wrong or what this awfull flavor is.

[mlaw06]

No I continued the same PBW rinsing schedule.

[Thirsty Boy]

well - you have gotten rid of your problem, and I am now convinced that leaving out the 5.2 isn't any sort of an issue, so if you never use it again and you never get the metallic taste again... the story has a happy ending.

Glad you have it sorted and thanks for prompting an interesting and informative thread.

TB

[Bill33525]

Have been brewing for several years before worrying about pH. Picked up some 5.2 and added to my hop bombs along with Gypsum, CaCl. All of a sudden was experiencing this after taste in the beer; But only after carbonation, just as mlaw06 posted. Seems if I purged the keg of CO2 and shook it, then applied 12 psi to the keg, the after taste was not as bad; May have over carbonated a bit. [recently started to carbonate through the liquid side to speed up the process].
Just brewed another hop bomb without 5.2, will report my findings.

Picked up a pH55 meter and found mash water pH can modified easily with a squirt of lemon juice. Tasted the waster and can not tell the lemon juice is in there. I altered my mash water to 5.1 and found my mash pH was 5.3 using that water.

Also found the temperature compensated pH55 meter registered the same pH at mash temp as room temp. Added lemon juice to my "batch sparge" water and found my final runnings out of the mash tun were 5.4... Can't wait to taste this beer!