pH of distilled water

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hector

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Hi there !

Does pH variation also occur in distilled water by temperature variation ?!

I mean , if distilled water have pH 7 at room temperature and if I add enough lactic acid to reduce it to 6.1 , then can I say that

the pH would be 5.8 at 160 F ?!

Hector
 
The pH of pure water does depend on the temperature. At 25 °C it is 7.00. At 20 °C it is 7.08, at 50 °C it is 6.63. Etc. But that's not really what you are asking. You are asking whether water treated with lactic acid has a pH which will vary with temperature and the answer is again 'yes'. Pure water which has been acidified to pH 6.1 at 70 °F with lactic acid would, theoretically, have a pH of 6.7 at 160 °F. This is because lactic acid becomes a weaker acid with increased temperature unlike water which becomes a stronger acid.

Note that I have carefully used the term 'pure water' instead of distilled water in the preceding paragraph. Distilled water will quickly pick up carbon dioxide from the atmosphere and its pH will, as a consequence drop. As so little lactic acid is required to cause the pH shift of pure water at 20 °C to 6.1 this also tiny amount of dissolved CO2 will have an influence on the observed pH. Without accounting for this calculated pH values are not terribly meaningful. Put another way, the buffering capacity of 'acidified' pure or distilled water is so small that other factors will doubtless override the dependence of the acid (or water's) pK's (a number which determines the strength of an acid and thus the pH of an aqueous solution containing that acid.
 
You are asking whether water treated with lactic acid has a pH which will vary with temperature and the answer is again 'yes'.

Thanks for your reply .

I should explain what I really mean by my question .

I'm an Extract brewer and I also use steeping grains . By the first batches , I used distilled water and by later ones , used bottled spring water .

But Tannin bitterness and Husky aftertaste was detectable by all of the Beers .

As I always steep the grains not longer than 30 minutes and by temps not higher than 70 C , I thought that this problem should be due to the pH .

The pH of the distilled water was 6.5-7.5 at room temperature and that of the spring water is 7.2 .

Therefore , I decided to adjust the pH to a lower level in order to get rid of that husky aftertaste .

What is the best way to do this ( preferably with distilled water ) , so that I can be sure that the pH by the time of steeping is below 6 ?

Hector
 
Mix the grain with the steeping water, and THEN cool it and check the pH. I doubt it's above 6, unless you are using very alkaline water, and it's probably closer to 5.5-5.8, depending on the grains you're using.
 
it's probably closer to 5.5-5.8, depending on the grains you're using.

I'm using Crystal malt ( 40 L ) as steeping grains .

As I said , I've had husky aftertaste by my previous batches . So , I think that I should do something with the pH .

I tested these grains before and they don't drop the pH effectively .

Hector
 
I have to echo what Yooper said. The distilled water pH of even base malts is below 5.8. A colored malt should have a distilled water pH even lower. If you are steeping crystal malt in distilled water and measuring pH above 6 then suspect your pH meter or buffers.
 
If you are steeping crystal malt in distilled water and measuring pH above 6 then suspect your pH meter or buffers.

There is nothing wrong with my pH meter and buffer solutions .

The Crystal malt I'm using is Home-made . I make them at home by using raw Barley .

Raw Barley --> Green malt --> Stewing --> Roasting in Oven

I had husky aftertaste by my previous batches with both distilled and spring water and it means that the pH was
above 6 by the time of steeping at 70 C .

What should I do to lower the pH below 6 ?

Hector
 
There is nothing wrong with my pH meter and buffer solutions .

...

I had husky aftertaste by my previous batches with both distilled and spring water and it means that the pH was
above 6 by the time of steeping at 70 C .

Did you measure the pH of the grain/water mix with your meter, or are you saying it must be above 6 based only on the taste?
 
Mix the grain with the steeping water, and THEN cool it and check the pH. I doubt it's above 6, unless you are using very alkaline water, and it's probably closer to 5.5-5.8, depending on the grains you're using.

Not here in st. Louis. I almost always have to add 0.5 ml to 1.5 ml to get the ph correct.
 
Did you measure the pH of the grain/water mix with your meter, or are you saying it must be above 6 based only on the taste?

As far as I know , there are three factors that affect tannin extraction from the husks :

- Duration of the steeping

- Temperature

- pH

I always steep at 70 C and for 30 minutes . So , the only remaining Cause of this aftertaste is the pH .

That was my Conclusion and I'm going to check the pH by the next batch .

Hector
 
I guess that means the answer to Huff360's question is that you did not actually check the pH.

When I wrote that if you are measuring distilled water pH for crystal malt above 6 you should check your meter I assumed that you were using properly prepared crystal malt. I'm not saying that yours isn't but as you aren't Weyermanns or Thomas Fawcett the malt itself is subject to question. The first thing to do, of course, is make a distilled water test mash with a sample of this malt and see if the pH is under 6. If it isn't and you were a professional maltings you would discard that batch as flawed. The second thing to do would be to try one of these beers with a professionally malted crystal and see if you get the same effect.

In any case in any situation where you wish to lower pH the way to do it is to add acid in small, controlled increments while monitoring the change in pH with a properly calibrated meter. If you are using LHBS bought 88% lactic acid it would probably be a good idea to dilute that down to 20 - 30% before adding.
 
As far as I know , there are three factors that affect tannin extraction from the husks :

- Duration of the steeping

- Temperature

- pH

Or perhaps we can add one more:

- Some crazy, funky characteristic of your home-stewed crystal malt.

I don't know what, why, or how the nature of homemade crystal malt may or may not result in adverse flavor contributions, but until there's a comparison batch brewed with professionally made malt, I'm going with that as a more likely source of the problem than pH.
 
The first thing to do, of course, is make a distilled water test mash with a sample of this malt and see if the pH is under 6. If it isn't and you were a professional maltings you would discard that batch as flawed. The second thing to do would be to try one of these beers with a professionally malted crystal and see if you get the same effect.

In fact , I already wanted to make a distilled water test mash with my Crystal malt . I searched the HBT and found a Thread which

you had taken part in . You said that since there is no minerals in distilled water , the pH would drop continuously and a constant pH

can not be measured .

I make my Crystal malt at home because there is no LHBS where I live and it's not possible to order such things online , either .

Besides , I tried once steeping using pale malt which I bought from a malting factory in my Country ( they don't make specialty malts ) and

I got the same result . Thus , I was sure that my problem is due to the pH .

You suggested to use lactic acid which I was going to do , too . But , you said before that this acid becomes weaker by high temperatures and

therefore the pH doesn't drop low enough .

Do you still think that I should try lowering the pH that way ?!

Hector
 
While it is true (or apparently true given the data I have found for the pK of lactic acid as a function of temperature) that it becomes a weaker acid as temperature is increased it is also true that it takes very little additional acid (about 2%) to compensate for this in going from room temperature to 160 °F. IOW if it takes 2 mL of acid to acidify a steep mash to pH 6 at room temperature then it would take 2.02 mL at 160 °F. The best way to see what is happening is to check the pH at the temperature involved but not many people want to subject their pH electrodes to temperatures as high as 160 °F. So perhaps you might try adding enough lactic acid to get the pH to 5.6 or so at room temperature. The lactic acid will tend to increase that pH as the temperature rises but the acids in the malt presuming there are some - there would be in commercial malts) become stronger as the temperature rises. The extra acid you use to get to 5.6 should be enough to insure that you are at pH 6 at higher temperature even if the distilled water pH of the malt is above 6.
 
While it is true (or apparently true given the data I have found for the pK of lactic acid as a function of temperature) that it becomes a weaker acid as temperature is increased it is also true that it takes very little additional acid (about 2%) to compensate for this in going from room temperature to 160 °F.

Thanks a lot for your Explanation . It helped me making a Plan to keep the pH below 6 by the time of steeping .

I will try it and let you know about the result .

By the way , I read an article yesterday and realized that the water-to-grain ratio is also important by steeping .

It will certainly make you wonder when I say this ratio by me is 4 qts./lb. !


Hector
 

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