Lactic acid for pH level reduction

How to use lactic acid to reduce the pH level of your home brew beer

If your beer's pH level is too high, you may want to use lactic acid to reduce the level.  This is especially helpful when making 'high malt' beers or if your water source is alkaline.

Also known as hydroxypropanoic acid, lactic acid is primarily found in sour milk products, such as koumiss, leban, yoghurt, kefir, and some cottage cheeses. Not blue cheese though.

When making beer, a sour taste is often not desirable, yet when seeking a sour beer flavor, using lactic acid is a great way to achieve the effect.

Adding lactic acid to the mash or sparge to reduce pH

Once you have mashed in and it has settled for a bit, it's time to take a pH reading with your trusty meter. If the result is too high, then it is time to add the acid.

The effect of the acid to reduce tannins in the beer.

How much lactic acid to add?

It's not a straightforward exercise. The grain bill can have an effect on your starting point. You can't simply add 1 ml per gallon and be done because you need to know at what level your pH is so you can bring it down to the desired rate (5.2. - 5.6 generally speaking) 

I've seen people use 1.5 ml to 2 per gallon and have good results.

There are some calculators out there which offer guidance, the Bru'n Water guide is a popular choice. 

If you guess and use too much, you will definitely make your beer taste sour. 

The key point around the amount to use is you need to have very accurate readings so use a quality pH meter.

What about lactic acid for sour beers?

This is a different use of lactic acid where you are using it to influence the taste of your beer rather than reducing the pH.

You can add lactic acid after primary fermentation to make your beer taste sour. 

If you are looking to make a more traditional 'sour beer' then the role of Lactobacillus bacteria in making sour beer comes into play.

Lactobacillus is part of a family of bacteria called "Lactic Acid Bacteria". The bacteria produce lactic acid as a byproduct of eating things from their environment. 

So, if you are a whizz in the brewery, you can use the bacteria to produce lactic acid to sour your beer.

Practitioners of this method sometimes actually 'pre-acidify' the wort with lactic acid to help ensure a suitable environment in which the bacteria and then go to town. 

Using phosphoric acid instead of lactic to reduce pH levels in beer

There are several chemical compounds that you can use to reduce pH levels in wort - gypsum (calcium sulfate) or calcium chloride are popular choices and so is phosphoric acid (which can also be used as a rust remover and is a common ingredient in sanitizers!),

There's a bit of chat on the forums about the difference between the two. 

Phosphoric is more arguably reactive and will drop the pH level quicker than lactic.

If you cut through it, they do the same job and neither of them appears to be discernable in the final product - this testing experiment seems to confirm that. 

Leave a Comment lactic acid, ph levels, sour beer, tannins