According to me beer making is not a very exact science for hobby brewers. It does not matter if you use a little too much malt or maybe even a different kind of hop. It will become beer.
So far I did not care at all about the pH of the water that I use. In the last beer that I brewed I decided to add some citric acid to the water as a test. To my surprise I ended up with a higher gravity than the previous time I made the same beer. Apparently the enzymes do work better at a lower pH.
Luckily a friend of mine has a very cheap pH meter that he bought from China so I borrowed it and did a test with it. According to a book I have, the enzymes work best at a pH between 5,2 and 5,6 so that was the target.
The pH is not a linear scale so it is not so easy to predict the result. So I just tried to reach it.
Normally beer makers use lactic acid or other acids but since I don’t have it I decided to use citric acid which is a nice fresh tasting acid.
First I took a measurement of the water that I use without any additions. The pH is 8,0.
Then I added 1 gram citric acid to 0,5 litre water. The pH went down to 2,8.
Obviously this was way too low so I diluted the solution by throwing away half of it and then add the same volume of water. The result was
1 gm in 1 litre -> pH 3,2
1 gm in 2 litre -> pH 3,8
1 gm in 4 litre -> pH 4,8
1 gm in 8 litre -> pH 6,1
Since my scale is not very accurate the above test is just an indication. I decided to use bigger quantities to be more accurate. I dissolved 10 gm citric acid in 500 mL water. Of this solution I used 5 mL. (Containing 0,1 gm acid)
Then I dissolved this 5 mL (0,1 gm) in 500 mL water. The pH measured 5,3.
So in conclusion; if you want to make 10 L beer you should add about 2 gm of citric acid. This is so little that obviously you are not going to taste this in the finished beer.
Calcium Chloride and pH
In this last beer I also used Calcium Chloride to soften the water. I am not able to do any measurements of the hardness so I used 2 gm per 15 L as per the recipe. (Actually I use 6 mL of the 30% CaCl solution which I use for cheese making)
I read somewhere on the web that CaCl also decreases the pH so I decided to test that as well.
First I measured the CaCl solution as is. The pH is 5,9. Not very low, so I assumed that it would not be a great influence.
And I was right. I dissolved 30 ml (=10gm CaCl) in 1 litre water. The pH went from 8,0 to 7,6
Then I added another litre water. 10 gm CaCl in 2 litres of water. The pH went from 8,0 to 7,8.
It is safe to say that CaCl additions do not have influence on the pH compared to citric acid additions.