How to measure mash pH

aussie brewer · Jun 19, 2019

Hi, i am using bru n water and usually adding acid malt to reach a mash pH of 5.3 for my pale ales. I wait 15 mins the take a sample from the top of the mash tun, cool it to room temp then test with my callibrated pH meter. I read a few comments about mash pH being higher than the cooled sample? am i doing this right? Cheers!

BobBailey · Jun 19, 2019

All pH readings should be taken at room temperature unless noted otherwise for a specific instance.

micraftbeer · Jun 19, 2019

Right process. Probably should wait until closer to 30 minutes based on feedback I've gotten through this forum, and my own sampling experience where the pH value changes on mash samples taken at 10 minute intervals throughout a 60 minute mash.

Qhrumphf · Jun 19, 2019

Mash temp will read *lower* than room temp. And it's not just an ATC thing- the mash chemistry changes as the temp changes.

I once read that as mash reactions happen at mash temp, it makes sense to read at mash temps.

There are two problems-

1) all the literature assumes room temp (Gordon Strong being the notable exception I can recall)

That's not a big deal as long as you're consistent in approach, but more importantly-

2) mash temp readings are really hard on a pH meter electrode.

I sample, cool, and read at about 20-30 mins.

cire · Jun 20, 2019

Even amongst the most acclaimed homebrewers there are differences of opinions about when mash pH should be measured and what reading is best. However, to compare your findings with those advised in recognised technical texts, the sample should be cool. Any reading taken at mash temperature will be quoted as such.

If possible recycle your wort before taking a sample. A small sample swirled in a heavy glass container taken from a freezer will be quickly cooled. When at 20C the sample can be transferred to a small plastic container at 20C for measurement of pH.

You may find that early readings can be misleading, although worth recording for future guidance. As the mash procedes, pH will begin to stabilise. pH readings of runnings are critical and if allowed to rise above pH 5.6, risk extracting components that are better left in the mash tun.