Ridiculously low pH in an ESB

[AdamPS1025]

Long time reader, first time poster...

My buddy and I had a double batch weekend on Saturday and things went great except for the pH on the ESB we brewed. Here's the specs that matter:

9.3 Gallons RO Water

Grist:
10 lb MO
6 oz C60
4 oz Extra Dark Crystal

Target Water Profile (Terry Foster ESB Profile):
Calcium: 75
Magnesium: 0
Sodium: 0
Chloride: 20
Sulfate: 150

Added 9.5g of Gypsum and 1.5g of Calcium Chloride to the water to hit the profile. Also used .32g of Potassium Metabisulphite.

Expected pH from Brewer's Friend was 5.34 and 5.45 from Bru'n Water.

With two different pH meters, both calibrated, the pH struggled to get above 5. One meter read 4.98 and the other read 5.01. Why was the pH so low? I've racked my brain and cannot figure out what went wrong. Does any one have any ideas? Thanks in advance.

Cheers!

Adam

 

[mabrungard]

So, no acid was added to the mash? No acid malt?

I know the Kmeta will drop the pH slightly and the healthy calcium salt dose will too. But that is quite a drop. How did you model the extra dark crystal? Isn't that like 120L?

 

[AdamPS1025]

Martin,

Thanks for the response. Given the salt additions and an expected pH of 5.37, I did not add anything to acidify the mash. No lactic. No acid malt.

The crystal was 160L.

 

[mabrungard]

That extra dark crystal is a very acidic product, but you're only using a couple percent. I don't see anything that would lead to a pH as low as you measured. Hopefully it still will taste OK. It's still going to be beer.

The one problem that you may observe is that the beer is a little thinner than you might expect. Proteolysis is enhanced at lower mashing pH and that tends to make the beer thinner bodied.