When is the BEST time to take a MASH pH reading

[AHarper]

When is the best time to take a reading?

My question revolves around adding Acidulated malt to the mash to reduce the "calculated" pH as it must take time for the acid of the malt to leech out into the mash and then, of course, it has to be mixed into the mash so you can get a best-fit reading.
Doing the sample at the start of the mash - when the lid is off and the grains mixed in - does not seem to be good enough for the acid levels to be accurate. Doing it at the end of the mash will only prove, or disprove, that the calculator in the recipe builder works as intended and then you will need to correct one way or another before adding the wort to the kettle.

Or does it matter at all? Just assume the recipe builder has it right first time, every time.

Suggestions please...

 

[Minbari]

I have always done it about 15 min into the mash. Seems to work

 

[Yooper]

I have always done it about 15 min into the mash. Seems to work

Yes, me too. Although by then it's a bit too late to actually change the pH much (if at all) before conversion is finished, it is worthwhile for next time for sure.

 

[HighVoltageMan!]

When acid is added to mash, the acid reacts very quickly even in the form of acidulated malt. If it's properly mixed into the mash, the pH can be measured within a minute or two, the reaction happens so fast. The mash pH can be measured right away, the pH stabilizes very quickly, the only way it will move is down. So if you measure with 5 minutes of strike and measure again 30 minutes later the difference is usually less than .1 or less.

 

[AHarper]

When acid is added to mash, the acid reacts very quickly even in the form of acidulated malt. If it's properly mixed into the mash, the pH can be measured within a minute or two, the reaction happens so fast. The mash pH can be measured right away, the pH stabilizes very quickly, the only way it will move is down. So if you measure with 5 minutes of strike and measure again 30 minutes later the difference is usually less than .1 or less.

I was meaning with respect to mashed Acidulated grain. Surely if it takes time for the sugars to leech out of the other grains, would it be safe to assume that the acid in the acidulated malt may take the same time or less? I'm not sure what the chemistry of it is.

Liquid acid I can agree works a lot faster - probably instantly but the malt must be slower to activate,

 

[HighVoltageMan!]

I believe the vast majority of the acid is formed by bacteria on the surface of the grain, so it should be pretty fast, although it may not be as fast as liquid.

 

[Dirty Dingo Brewing CO.]

When acid is added to mash, the acid reacts very quickly even in the form of acidulated malt. If it's properly mixed into the mash, the pH can be measured within a minute or two, the reaction happens so fast. The mash pH can be measured right away, the pH stabilizes very quickly, the only way it will move is down. So if you measure with 5 minutes of strike and measure again 30 minutes later the difference is usually less than .1 or less.

^^^

Second this. You want to start reading your pH basically immediately. If you don't fix the pH in the first 10 mins or so, you'll lose whatever efficiency you're trying to save anyways.

P.S.- Keep in mind it is always easier to go down than up. So if you're unsure about the chemistry at the start of the mash, err on the high pH side, so you can easily add an acid (acid malt, ascorbic, citric, whatever) and bring it down quickly. Whereas if you are low, say 5.0, it'll take probably 70gms or more to get back into the correct range.