Mash pH question

[StevieDS]

Yesterday I brewed a dark mild. I used Brun water for my water treatments and according to it, my mash pH should have been 5.3 (pretty much perfect).

However when I tested a sample, cooled to 20c, about 15 mins after dough-in, it was pH 5.8.

I know that is still in the acceptable range, and I know the Brun water software can't be totally accurate, too many variables, and water ion content can change from day to day.

However I'm a bit of a perfectionist with stuff like this and it just got me thinking...

Is there a simple way I could work out in future how much lactic acid I'd need to add to hit optimum pH?

If I know the current pH, water volume, grain bill, mash temp and acid strength, is it possible to work it out?

Thanks, Stevie.

 

[Runwell-Steve]

When did you last test your Alkalinity. All this rain has had a big effect on some people's water supply.

 

[dennisdk2000]

I daresay there is a way of working it out, but I doubt it'll be simple. Working out the pH and how to manipulate it using weak acids and buffer systems was part of my chemistry lessons at college many years ago, but we never worked with anything as complex as a mash. You'll need to look up the pKa value for the lactic acid, and you might even be able to work out an empirical value for the pKa for your grain bill. Then there's some not too complicated maths, most of which I can't recall in any significant detail.
Best bet is to see if Bruin Water can work it out for you, or if by playing about with it you can get your desired result.
Hope this is of some help...

Dennis

 

[pittsy]

A way to correct (lower) the mash ph is adding acid malt ( i also use lactic acid and acid malt) by 1% of the grain bill should lower your mash ph by 0.1 . If like me you use lactic acid for water treatment then acid malt is ideal too .Info says upto 3% with no sour effect but if using to lower mash ph then more like 5% before any tartness will be present ( to get sour at least 8% would be needed ) .You can test your mash ph and add acid malt to correct quite easily within reason P.s brun water includes acid malt in it .

 

[StevieDS]

Thanks for the replies.
Pittsy, sorry just to clarify what I meant was, if I start my mash then about 10 mins or so into it I test the pH and it's too high, can I work out how much acid to use to adjust it?
I think Brun water is great, I always use it for water treatment, but there are so many variables it won't always be 100%, understandably.
I'm not sure how easy it would be to work this out, as DK says, the chemistry is probably pretty complex.
In response to rs, I know I need to test alkalinity each time I brew, which I didn't, another probable reason for the discrepancy

 

[pittsy]

Lactic acid can only be added to room temp water . I know you want the formula for working it out but you can do it manually by adding acid malt at 1% for 0.1ph drop while in process of mashing .

 

[Aleman]

In response to rs, I know I need to test alkalinity each time I brew, which I didn't, another probable reason for the discrepancy

being blunt if you don't then there really is no point in using BrunWater. The Alkalinity will change with all the rain, but what that means is that it should drop, meaning that the mash pH should be lower, as you should have an alkalinity lower than the last time you brewed . . . If you are going off a water report

There really isn't any way to determine how much acid to add either, as the mash is effectively a buffer . . .you keep adding acid and stirring and nothing happens . . .then all of a sudden it drops way lower than you wanted so you are in the process of adding bicarb to bring it back up and you start chasing your tail.

Pittsy's suggestion of acid malt is a good one, but only if you have taken care of your alkalinity properly in the first place, and it sounds as though you haven't actually done that as you pH is too High.

Measure the alkalinity . . .adjust it . . .measure it again . . . if its where you want it . . brew . . . if not get it where you want it . . . and then brew

 

[StevieDS]

In response to rs, I know I need to test alkalinity each time I brew, which I didn't, another probable reason for the discrepancy

being blunt if you don't then there really is no point in using BrunWater.

I know, my bad
I usually brew with RO water so I can build the profile from scratch however this was a bit of an impromptu brewday and I hadn't any RO so I used tap water and a water report.

(IMHO water reports seem to be a waste of time and pretty useless to a home brewer anyway.)

As for adding acid malt, would that not have the same result as adding lactic acid? I thought it was just malt laced with lactic acid? Surely the pH buffering of the mash would still apply?

Anyway, lessons learnt:
1. Measure alkalinity EVERYTIME
2. Make sure alkalinity is adjusted BEFORE mash-in
3. Don't trust water reports

I think I'll stick to RO water in future