BIAB Mash pH Help

[norocky]

I switched to BIAB a few batches ago. All was good until my last brew had a very astringent taste. It was a very light beer and my conclusion was a faulty mash pH. In an effort to eliminate another variable and hopefully improve the beer I decided to brew this weekend using 100% distilled water. I ran the numbers through Bru'n Water and EZ Water shooting for a Pale Ale profile and ended up with a suggested 12g Gypsum, 5.6g Epsom Salt, and 3.2g Calcium Chloride. Combined with 1.6ml of lactic acid, both programs predicted a mash pH of 5.4 for the 8 gallon mash of Northern Brewers Dead Ringer.

After stirring the mash for a few minutes I pulled out the pH meter and got a reading of 4.6. This reading was taken around 135 degrees. I expected to see something like 5.1 since everything I read said the hot temperature would make a .3 or so difference. I went back inside to check the calibration on the scale and pH meter. After realizing both were fine I went and checked the mash pH a second time (10 minutes in) and got 4.6 again.

This is the first time I have attempted to use the pH meter so my guess is this is user error or something is up with the meter. Any thoughts?

 

[ajdelange]

How much water? How much grain? What types of grain. Give us those and we can estimate what kind of pH to expect (but it will be a rough estimate).

In the future, be kind to your pH meter. Take readings at room temperature and calibrate at the same temperature. See the sticky on pH meter calibration.

 

[norocky]

8 gallons of distilled water. 11 lbs of 2 row and 1 lb of caramel 40.

 

[ajdelange]

That should give a mash pH of about 5.33 at room temperature which would be closer to 5.2 or so at mash temperature. This is based on a fairly acidic base malt (DI pH 5.62). All that calcium drops the pH almost 0.15 so you don't need the lactic acid. Without it pH would be about 5.4 or just about right.

OTOH if you use a base malt with higher DI mash pH at around 5.8 you could expect the mash pH to be as high as 5.53 without the lactic acid and 5.44 with. In this case the acid would be desirable. A lot, thus, depends on the base malt DI mash pH which is why pH estimation schemes aren't very robust unless the actual malts being used have been measured in the lab.

 

[norocky]

Thanks for the reply. So if you had to wager a guess as to why I got a reading around 4.6 what would it be? Since I used distilled water and the scale proved accurate to within .1g I have to assume it was the pH meter or something I did with the pH meter. I calibrated a brand new Hanna 98107 with fresh room temperature samples of 4.01 and 7.01. Is it possible that simply measuring close to mash temperature caused this reading or do you think something else was going on here? Thanks for the help.

 

[ajdelange]

Thanks for the reply. So if you had to wager a guess as to why I got a reading around 4.6 what would it be?... I have to assume it was the pH meter or something I did with the pH meter.

I'd start by looking there. This particular meter has 0.1 resolution so that, for starters, there is a built in error of 0.029 pH in every reading. RSS that with the 0.02 error from typical technical buffers and you have 0.035. The meter is not equipped with ATC so there will be error from measuring at mash temperature but none of these come close to explaining a reading of 4.6 on something which most probably has a pH well over 5.

If new to pH measurement you are going to get some squirrely readings. There is a learning curve. This is why I suggest that new users practice with common household substances and liquid foods such as milk, eggs, sodas and beer (of course).

Unfortunately these inexpensive meters tend to be unstable which means that calibrations are not held for more than a few minutes. There is an article at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/ which describes a test you can do to check on the abilities (or lack thereof) of your meter with regard to this important quality. I'd suggest you run a stability check as described in that article.