Acidic crystal malt?

Hi everyone,

Lately my beers have been cloudy and had a slight sour note to them. Of course I suspected an infection, and I went to the usual extremes to eliminate any possible source. With no result.

Then I realized that this problem started when I got in a new batch of malts. Could there be a lactic acid bacteria infection in the malt, thus producing lactic acid in or on the malt which was then carried forward (as acid, not as a bacterial infection) into the mash, the boil and the fermenter respectively?

So I decided to do some pH measurements on my various malts (at least the ones used in the problem beers). And I got some weird results.

I took 50 grams of each malt, crushed it (using mortar and pestle, cleaned between malts so as to avoid cross-contamination, rather than the usual malt mill) and steeped them in 150ml of water at a starting temperature of 70 degrees. (Obviously i'm not overly concerned about mash efficiency, enzyme health or tannin extraction here). Then a quick stir with a clean plastic spoon, and a pH measurement using indicator strips.

My water comes through a borehole (well) from a limestone layer at about 30m depth, and is therefore rather alkaline. I measured the pH of the water as well.

I measured the following pH values:

• Water (same sample used for strike water) - 6.2
• Pale malt (American 2-row, imported as barley and malted locally) - 5.8
• Crystal 60L, imported from Germany (Weyermann's maltings) - 4.5
• British Crystal 95-115, imported from UK (Baird's maltings) - < 4.5*
• Black patent malt 525L (produced locally) - 5.0

* (indicator colour was off the scale, indicator package did not show colour indicating pH lower than 4.5)

Give the fact that I have used Baird's crystal extensively, that's the first one I might want to change to see if that's the problem. I should also note here that the origin and age of the various imported malts are not known to me, so they could very well be dodgy - I'm in Africa after all.

Now the water sample and the pale and black malts look more or less like what I would expect. What I cannot explain is the weirdly low pH value on both the C60 and the British crystal. Yes, both are imported, but from different sources. One could be dodgy, but two? The literature I have seen suggests that the pH of crystal malts should be somewhere between that of pale and black malt.

What could be going on here? Suggestions anyone??

// FvW

What literature is indicating that the pH of crystal malts should be between pale and roast malts? There is none that I know of. But I do know of literature that indicates that your observed results are exactly as expected. Dark and medium crystal malts do have more acidity than roast malts. If those latest beers have included a dose of crystal and your water source has modest to low alkalinity (or you have acid treated your mash water), its quite possible that you have produced too low a mash pH and that could also produce a too low wort pH.

I do recommend that you read the Water Knowledge page on the Bru'n Water website. It will help explain this grain acidity issue you are having. There is also a chart on the opening page of the Bru'n Water website that shows how the use of dark crystal malt can really drop the mash pH.

Enjoy!

I would say you need to isolate the water variable by using a jug of reverse osmosis water if you can find it. Add only recommended amounts of minerals you can find at your local homebrew shop to adjust pH. See if it isnt the tap water as suggested above.

Hi, Martin,

mabrungard said:

What literature is indicating that the pH of crystal malts should be between pale and roast malts? There is none that I know of. But I do know of literature that indicates that your observed results are exactly as expected. Dark and medium crystal malts do have more acidity than roast malts.

Click to expand...

Believing that to be incorrect but unwilling to dismiss your answer out of hand, I spent a few hours reading up and Googling extensively. And it turns out that you are right and I was wrong. It looks like I've either overlooked some of what I read or misinterpreted it, but indeed dark and medium crystal malts are more acidic than black malts.

Which answers my question on the acidity of malts, but leaves me with the one about what had made my wort so acidic.

mabrungard said:

If those latest beers have included a dose of crystal and your water source has modest to low alkalinity (or you have acid treated your mash water), its quite possible that you have produced too low a mash pH and that could also produce a too low wort pH.

Click to expand...

It's possible. But would that actually be carried forward into the fermenter and give me a slightly sour undertone in the flavour of the beer?

mabrungard said:

I do recommend that you read the Water Knowledge page on the Bru'n Water website. It will help explain this grain acidity issue you are having. There is also a chart on the opening page of the Bru'n Water website that shows how the use of dark crystal malt can really drop the mash pH. Enjoy!

Click to expand...

I will definitely do that. Thank you!!

// FvW

There is nothing wrong with your results. (Other than pH test strips are not terribly accurate, they are, relative to each other, telling the correct story) For centuries, this is why areas of the world with more alkaline water brewed darker beers. Darker kilned malts naturally bring more acid to the mash. Especially dark crystal malts.

Here's a good visual aide, Kai has a lot of great stuff.

Edit: Guess I can't link to his image. Here's the page:
http://www.braukaiser.com/wiki/index.php?title=Mash_pH_control


You should check out his page if you're into this sort of thing.
www.braukaiser.com

frankvw said:

But would that actually be carried forward into the fermenter and give me a slightly sour undertone in the flavour of the beer?



// FvW

Click to expand...

Yes, certainly. I'm not Martin, but I can say that certainly if you have a low mash pH, the tartness would carry over into the flavor of the beer.

frankvw said:

It's possible. But would that actually be carried forward into the fermenter and give me a slightly sour undertone in the flavour of the beer?

// FvW

Click to expand...

Sourness is perceived in a number of ways. pH has an effect, but the anion associated with the acid has a substantial effect too. For instance, Malic acid is that stuff they use on sour balls. The pH isn't crazy low, but it sure seems that way.

A couple of tenths pH low may not be noticeably sour.