Low mash pH with Golden Promise

[user 141939]

Hello. I am using bru'n water spreadsheet and a good pH meter and I think I am finding that everytime I use golden promise my actual mash pH is lower than predicted.

Just wanted to see if this happened with other people. Typically I use rahr two row malt or castle pilsner. I've made several with Fawcett marris otter. Light beers, dark beers, bru'n water usually gets me very close to what I measure.

I did a mild using all golden promise for base malt and mash pH was about 0.3 - 0.4 less than expected. I've made two other beers including the one I made today that were lower. Today's was 44% golden promise and mash pH was about 0.2 less than expected.

Not a big deal I'll just target a higher pH from now on when using it. Just surprised I couldn't find anything about this since so many people use bru'n water and golden promise seems to be popular as well.

Just for more info, I have super soft water and general add gypsum and/or CaCl2 to get calcium up to about 60 ppm and chloride/sulfate end up around 60 - 80. I then either use phosphoric acid at 10% or acid malt to lower pH and baking soda if I am doing dark beers.

 

[ajdelange]

This simply means that Brun doesn't model Golden Promise very well. I believe it uses type and color to deduce mash pH and buffering. Try rerunning your numbers with a darker malt and/or darker color to see if you can get a better match between prediction and what you measure.

 

[user 141939]

Ok thanks. So if I change the color of Golden Promise in Bru'n Water from 3L to 10L, now my estimated mash pH matches exactly what I observed. At 3L predicted was 5.40 but observed was 5.20. At 10L predicted mash pH is 5.20.

Now I can lower my %10 phosphoric acid addition from 3.5 mL/gal to 1.5 mL/gal and this will give me a "new" predicted mash pH of 5.40 which is what I was targeting.

My first thought was just to target 0.20 pH higher than what I wanted (so I would target 5.6). I hadn't thought to play around with the color for the golden promise. Changing the color makes way more sense. I can't even get 5.6 without adding baking soda (according to bru'n water). So the two approaches aren't even giving me the same results.

So I will try predicting mash pH when using golden promise by calling it "10L" and see where that gets me.

 

[ajdelange]

Well this seems like a sensible approach but I'd feel a lot better about it if Martin would comment.

 

[mascervesa]

I used the same percentage of Golden Promise in a beer this weekend and noticed the same effect with a lower pH measured than predicted. Luckily I started with only 1ml of lactic acid instead of 3 ml that I was going to add, then checked ph after 20 minutes or so and it was 5.35. I think AJ is right that it is not modeled very well at 3L.

 

[user 141939]

Oh nice so I'm not alone! I'll update with my plan to use 10L and how that works out.

 

[jjeffers09]

I am seeing this on a couple of forums. GP has been dropping pH everywhere. I wish I understood why...

 

[user 141939]

Hmm. I guess my Internet searching skills failed me. I could not find anything on the matter.

If it's just the way golden promise is, then that's fine. If it's some kind of new phenomenon then that would be annoying.

 

[TenaCJed]

I could not find anything on the internet other than this post. I have interest in this subject as I am about to do a brew with a base of Simpsons Golden Promise.

 

[ajdelange]

I am seeing this on a couple of forums. GP has been dropping pH everywhere. I wish I understood why...

It's because each malt reacts to exposure to acids and bases in a different way in the mash tun. In particular we can measure the pH of a minimash of the malt in distilled water and then do the same for mini mashes to which various known amounts of acid or base have been added. Plotting the acid addition against the pH and fitting a curve gives a formula for the amount of acid required to set the malt to a particular pH. That formula is

mEq/kg = a1*(pH - pHdi) + a2*(pH - pHdi)^2

Each malt has different pHdi (the pH of the mini mash with DI water) and buffering charaterisitics (a1, a2 - often only a1 need be considered). Until someone makes measurements on this malt we will not know what pHdi, a1 and a2 are.

Kai Troester made measurements on lots of malts and noted (as have others) that pHdi and the logarithm of malt color are correlated from which he deduced that the acid base properties of a malt could be deduced from the colors and that is, I believe, the approach that Brun'n Water takes. The obvious problem with this approach is that, as is the case with Golden Promise, the color is not a particularly good predictor (Pearson's r = 0.92) of pHdi (or a1 but I have no idea how Bru'n derives a1 from color probably just uses the average value of -50 mEq/kg•pH). As color apparently controls what the program thinks pHdi is the obvious fix is to tell it the color is whatever it takes to get the right answer out of it.