mash ph problem

[tommyk]

So I recently purchased a ph meter and have been trying to dial in my mash ph. Yesterday was the first time I used it and after 45 minutes in the mash my ph read in at 4.8 at ~70F (meter was calibrated using 4 and 7). I used deionized water from whole foods in columbus ohio. I used the distilled water option in brunwater and plugged in my grain bill and salts and it estimated it at 5.2. Here is the info from the mash.

water
- 5.2 gallons deionized water
- 4.1 grams gypsum (0.8 grams / gal)
- 2.6 grams calcium chloride (0.5 grams / gal)

grains
- 14# 2 row 84.5%
- 1.5# munich malt 5L 9.1%
- 0.5# carapils 3.0%
- 5oz acid malt 1.9%

mashed at 150F for 45 minutes, vorlauf with pump for 10 minutes and than checked the ph. I am just trying to figure out why the ph was so low (4.8). Right now I am thinking the water I am getting is not the same mineral profile as the distilled water in brunwater. I really don't know, but I am going to try and contact the company that runs the water system and see if they have any information before I buy a wards report. Am I missing something obvious? Any help is appreciated.

 

[ajdelange]

I am just trying to figure out why the ph was so low (4.8).

It probably wasn't. Did you do a cal/stability check on your new meter?

Right now I am thinking the water I am getting is not the same mineral profile as the distilled water in brunwater.

I'm sure it isn't but that shouldn't make any measureable difference. DI water is effectively DI whether it be 18 MΩ or a couple ppm TDS.

I really don't know, but I am going to try and contact the company that runs the water system and see if they have any information before I buy a wards report. Am I missing something obvious? Any help is appreciated.

The obvious thing to check is the meter's stability. Do the check in the Stickies. People just starting out in pH measurement often get the most amazing measurements until they get the hang of pH measurement. You can't just pick up a Strad and play the Solo Partitas if you haven't done it before and while the training isn't quite so arduous with pH measurment there is a learning curve.

 

[tommyk]

I calibrated it just before I did the check, and it reads the 4.0 and 7.0 buffer solutions spot on. I left the meter in for minutes at a time, but it stabilizes in a minute or two usually.

I also tested the OG sample at room temp and it read 4.8 as well. Not sure if the ph changes during the boil, but it did read the same.

 

[ajdelange]

A mash with the composition you described should have a pH of about 5.35 or so (depending on the acidity/alkalinity of the actual malts you used) so 4.8 is not a reasonable reading and attention, therefore, focuses on the meter and its calibration. The calibration check and stability test described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/ will insure that your meter is stable and has been properly calibrated. It is not uncommon for the inexpensive meters that home brewers often use to accept calibration and then zoom off into hyperspace within a few minutes though an excursion of 0.5 pH is unusual. It's typically a couple of tenths or less. That is why it is important to check the buffers immediately after cal, 5 minutes after, 10 min after etc until you have confidence in your meter and the calibration procedure. We do note that you specified the pH as 4.8 which suggests that you have one of the ultra-cheapos that only reads to 0.1 pH in which case perhaps the 0.5 drift isn't that surprising. OTOH you might have rounded to 1 decimal place before posting.

With experience you will be able to tell when a pH reading doesn't feel right. This time the discrepancy is large enough that your instinct responded without extensive experience as well it should. When you get a reading that is out of line the first thing to do is check the meter against the buffers (assuming they are fresh, have not been contaminated, etc.). Even very good meters are subject to occasional out-in-left-field readings as, for example, if a husk particle blocks the junction.

Another clue here that points to the meter is that the pH didn't change after the boil. It should drop a couple of tenths.

You are not the first guy to be lead into the woods by a new pH meter (and I include myself in that number). It is good that you didn't panic and drop in a bunch of lime or bicarbonate. The beer is probably OK.

 

[mabrungard]

DI water should be equivalent to distilled water, with essentially no ionic content...pure.

I agree that it seems that the mash pH measurement should have been higher than 4.8. It should take more acid to drive the pH that low. I'm assuming that you cooled the sample prior to measurement, since measuring hot wort will report a lower pH.

One thing to recognize, is that acid malt is a natural product and may have variability. The original data that Kai Troester published regarding acid malt acidity showed much higher acidity/kg. That acidity would produce more than the typical 0.1 pH drop per percent of grist rate that we like to use as a rule of thumb. So that is a possible problem. Acid malt in Bru'n Water has been tailored to produce the 0.1pH/percent grist value. That and high acid malt acidity might be what created this problem. I dislike acid malt for this reason...you just don't know what you might get. That is far less the case when using a liquid acid of known strength.

 

[ajdelange]

. The original data that Kai Troester published regarding acid malt acidity showed much higher acidity/kg. That acidity would produce more than the typical 0.1 pH drop per percent of grist rate that we like to use as a rule of thumb. So that is a possible problem.

Kai measured two sauermalz samples but did not do a complete titration so I have to 'linearize' his results to use them. The two samples had essentially the same DI pH so the question is as to the buffering. One sample shows 138 mEq/kg-pH and the other 158 based on his data. Assuming the "2 row" behaves something like Weyermann's pneumatic Pils the 1.9% suaermalz in this case produces only 0.11 shift in pH for the stronger of the two and 0.10 for the latter i.e. about 58% of the rule of thumb value. So it is with rules of thumb.

Acid malt in Bru'n Water has been tailored to produce the 0.1pH/percent grist value. That and high acid malt acidity might be what created this problem. I dislike acid malt for this reason...you just don't know what you might get. That is far less the case when using a liquid acid of known strength.

I don't think we can blame the sauermalz here. I've heard rumors of 'double strength' sauermalz but you would need quintuple strength to explain an discrepancy this big.

I've never really looked at a calculation of pH shift vs rule of thumb before. It looks as if the Weyermann rule may be optimistic but I would really need to titrate some of their malt rather than rely of Kai's data before coming to that conclusion.

 

[tommyk]

I don't think I have a terrible meter... It is the Oakton ph1 ecotest located at the link below. I had already gone through getting the ph meter setup a few weeks ago, this was just the first time using it to check my mash.

I will run through the calibration / stability check, but this is how I read 4.8 on brew day. Hopefully its the meter, thanks for all your help guys. I will update as I find more.

Pulled meter out of cap that was soaking in 4.0 solution.
Rinsed it off using tap water.
Poured fresh 4.0 and 7.0 buffer solution it shot glasses.
Poured ~70F wort into a shot glass.
Calibrated ph meter in 7.0, then rinsed with tap water
Calibrated ph meter in 4.0, then rinsed with tap water
Check each one again, rinsing after each test (they read spot on)
Check wort, says 4.8 (I think thats strange so I do the following at least 2 seperate times)
Rinse, check 4.0 (reads correct)
Rinse, check 7.0 (reads correct)
Rinse, check wort (reads 4.8)

Just kind of stumped on how the meter would read the solutions right multiple times, but not read the wort correctly multiple times all within minutes of each other. Again I will be running through the stability check and see if I find anything else out. I may also try and do a little science test and use two different waters and a mini mash to check what ph should be based on tests done, what I read with DI water, and what I read with bottled distilled water. Thanks for all the help so far!

http://www.amazon.com/dp/B00FZSUN68/?tag=skimlinks_replacement-20

 

[ajdelange]

Things are definitely strange here. This isn't the greatest meter for brewing. For one thing it only has the 0.1 resolution. For another, it only does one point calibrations. IOW you aren't calibrating it for 4 and 7 but for one or the other (the last one). If you calibrate with the 7 buffer you are compensating for the electrode's offset and using a nominal value for the slope. If you calibrate at 4 or 10 you are measuring the slope and using a nominal value for the offset. This is OK for samples with pH near 4, 7 or 10 but mash is, WRT to single point calibration, in the worst place it could possibly be - about half way between 4 and 7. All of that notwithstanding, if you calibrate at 7 and then at 4 (so the 7 reading is thrown away) and the meter reads correctly in both buffers at the completion of cal that means that the assumed offset is close to the electrode's offset and the meter is 'calibrated'. If you come back a few minutes later and the readings are still correct in both buffers that means it is still calibrated i.e. that it is stable. With respect to those buffers. If the buffers are contaminated then, of course, all your actual pH readings will be off.

With what you have told us there is no way the mash pH could be that low. You would need an acidulated malt five times as acid as the normal acidulated malts or some other source of acid or a huge error in weighing out the acid malt or the water treated with acid before mashing and it would have to be fairly dramatic acidification.

I can't think what to suggest at this point other than to measure the pH of a DI water mash of MO (should be about 5.6), some 5 Star 5.2 (if you have it) in DI solution (should measure close to 6), a half tsp of baking soda in a glass of water should measure about 8.3.