First all grain brew mash pH question

[Simonh82]

I got my first AG brew under my belt yesterday. My attempt at a clone of Wild Beer Co Bibble (my recipe can be seen here http://www.thehomebrewforum.co.uk/showthread.php?t=59315). It seemed to go well. I got 80% efficiency so it will be a bit stronger than I had planned.

One thing that concerned me is the mash pH which I took 20 min in to the mash. I was using Johnson narrow range test strips and dunked it straight into the mash. It suggested the pH was around 4.6 so very low. What would be the effect of a mash pH this low?

I don't know how accurate the test strips are but I've no reason to doubt them. I know may people will say you need a decent pH meter but for the moment that isn't an investment I can afford, after upgrading to AG.

My efficiency was fine so I guess the mash worked but will there be any effect on the taste or fermentation.

The local water report that I found online suggested a very high alkalinity and bicarbonate level, so I made some acid additions to get it down. It looks like it might not be as alkali as I thought and I could have gone too far.

I've just sent off a sample for analysis so I will know what my water is actually like, rather than relying on online reports.

Might I have done any damage by letting the pH get this low?

 

[kev211]

Did you measure the mash ph at room temperature or mash temperature? The temp plays a role on pH, and if I recall the difference between them can be worked out to about 0.3.

So if you took the mash ph at mash temps and got 4.6 then your actual room temp ph should be closer to 4.9.

Either way, I think you should probably be fine (that being said, my general working knowledge of chemistry/ph is slim). For your first all grain brew youre miles ahead of most first time AG brewers after their first brew (myself included).

 

[TheMadKing]

test strips are very inaccurate and should be considered no better than taste-testing for pH.

You're much better off investing in a decent quality meter when you can afford it.

In the mean time, just wait for your water report and input the results into Bru'n water and use that as a guide.

 

[kev211]

Bru'n water and use that as a guide.

Ditto to this. Bru'n water is pretty much spot on. I usually nail my pH when using the spreadsheet.

OP, what was your recipe and water profile you found online?

 

[Simonh82]

I did take the pH at mash temperature so maybe it isn't quite as bad as I thought.

I was using Bru'n Water after seeing it recommended so highly on this forum. I think the problem is that I was using a generic water report for the local area.

The source was given and it isn't too far away (1-2 miles as the crow flies) but who knows how much the stuff coming out of my tap will vary from their analysis.

The report said there was very high alkalinity 251ppm CaCO3, with a total bicarbonate level (worked out by Bru'n Water) of about 600ppm. I had to make quite substantial acid additions to get it down for this pale beer.

Hopefully the proper analysis will show my water isn't actually this hard. I guess it is wait and see time.

 

[Simonh82]

Ditto to this. Bru'n water is pretty much spot on. I usually nail my pH when using the spreadsheet.

OP, what was your recipe and water profile you found online?

The water report is here https://secure.thameswater.co.uk/water-quality-reports/2014%20WQ%20Report_Z0113_putney%20heath.pdf (pdf). It is provided by my water company based on post code.

The recipe is at the top of this thread http://www.thehomebrewforum.co.uk/showthread.php?t=59315. I ended up using an extra 100g of Marris Otter but I don't think that would make much difference.

 

[ajdelange]

First, as has been mentioned, pH strips are not reliable in beer making. But they tend to be off in the low direction by about 0.3 so that we might guess that your true pH was closer to 4.6 + 0.3 = 4.9 which is still much lower than desired which still does not mean the beer is lost even if the pH is actually that low.

I can find nothing reported about alkalinity in your water report but can calculate that it would be about 288 ppm as CaCO3 because it would take that much to electrically balance what they do report at pH 7.718. That's a lot and will require a bunch of acid to neutralize viz. 123 mEq using Munton's Maris Otter or 101 using Crisps under the assumption you mashed with 10 L of this water. That means 100 - 120 mL of 10% phosphoric acid or the equivalent in other acids. About half the acid (52.5 mEq) is required to deal with the water alone. Tell us what kind of and how much acid you actually used and we can give you a better idea. If it is much more than 100 - 120 mL 10% phosphoric equivalent then low pH is to be expected.

 

[Simonh82]

The report has total hardness as CaCO3 at 251ppm. This was the figure I used in Bru'n Water.

I was using BIAB so my mash volume was 25L. To this I added 22.5ml of CRS solution and 13.75g of Malic Acid, targeting a mash pH of 5.36.

In my 12L of sparge water (I only used 6 in the end), I used 4.8ml of 80% Lactic Acid and 4ml of 75% phosphoric acid.

I had to use various different acids to keep them under the taste threshold.

 

[ajdelange]

First and foremost: In yesterday's post I indicated about 10 - 12 mL of 10% phosphoric acid would be required. That's per liter and so the total amounts for 10L would be 100 - 120. I've corrected that in the post.

The report has total hardness as CaCO3 at 251ppm. This was the figure I used in Bru'n Water.

As this is your first AG you can hardly be expected to be familiar with many of the nuances but a total hardness number of 251 actually means that the analyst that measured the total hardness used 5.02 mEq (milliequivalents) of EDTA (the stuff they use to do hardness tests) to chelate (remove) the calcium and magnesium from a liter of the water. The archaic practice of multiplying that number by 50 (half the molecular weight of calcium carbonate) and reporting "Total Hardness as CaCO3: 251 mg/L (ppm)" is apparently still alive and well in the UK as it is in the US. This confuses so many people I wish they would just stick to mEq/L but I don't think I'm going to get my way on this. Anyway, the 'calcium carbonate' here has nothing to do with carbonate or bicarbonate (the sources of alkalinity) but rather with calcium and magnesium. If a water sample has modest sodium, sulfate, fluoride, nitrate, iron, chloride etc. then the alkalinity and hardness are approximately equal as is the case here: 251 ~ 288 (15% difference).

I was using BIAB so my mash volume was 25L.

For that volume of this water you would require 132.6 mEq of acid for the water alone. The grains would require another 56 but you get a credit of 17 for the calcium and magnesium (assuming that 3 of the 5 mEq/L of hardness is attributable to calcium) for a grand total of 169.3 mEq. These numbers all require assumptions on my part and so can only be interpreted as estimates.

To this I added 22.5ml of CRS solution

CRS is 3.87 N so 22.5 mL gives you 87.1 mEq.

and 13.75g of Malic Acid, targeting a mash pH of 5.36.

That's a lot! In fact 13750/134.09 = 102.54 mmol. Malic acid, at pH 5.36, yields 1.59 mEq of H+ per millimole of acid or, in this case 162 mEq. That's almost the total requirement and with the addition of the CRS would definitely put you substantially under your target pH. Estimated pH would be 5.08 which isn't too far from what we guessed yesterday by putting 'English' on the pH strip reading.

Spreadsheets are great but all of them have some shortcoming or other and can, under certain circumstances send you wide astray as apparently happened here. This means that you need to be able to say "Whoa, that doesn't seem right!" but, of course, the problem is that you can only do that after you have garnered lots of experience preferably laid on a foundation of understanding of the basic chemistry. This is an investment many are not willing or able to make.

Getting a water report is a first step. It will indicate an alkalinity of around 288 but it won't be that number. Your misinterpretation of the data you have did not result in a serious error so let's look at a back of the envelope approach to the problem based on the 250 number you assumed. You must dispose of the alkalinity in the water and the alkalinity in the grain. 'Dispose of' here means you must 'remove' about 90% of the reported water alkalinity. In this case 90% of 250 is 225. The AMS/CRS data sheet says that 1 mL of the stuff per liter will remove 192 ppm alkalinity. Thus to take care of your water you need 225/192 = 1.172 mL/L or, for 25 L, 29.3 mL

Each kg of base malt requires 30 - 40 mEq of acid to move its pH by 1 unit. Typical base malts have DI pHs of 5.7 - 5.8. Thus if you are going to move 2.7 kg of MO from 5.75 (average) to 5.36 you are going to need another
2.7*(5.75 - 5.36)*30 = 31.59 mEq
As CRS is 3.87 N that means another 8.2 mL CRS for the base malt. So a total of 31 mL of CRS is roughly what you need. If a spreadsheet tells you you need twice that there is a problem. My guess as to what happened here is that the spreadsheet assumes malic acid produces 1 proton/molecule when it is actually, as we noted earlier, more like 1.6.

 

[Simonh82]

Thank you for the very detailed reply. When I'm not at work I will have a proper read through this and see if I can get my head around it.

The water report that I've sent off for says that it provides the following analysis:

• pH
• Alkalinity (as CaCO3)
• Nitrate
• Calcium
• Chloride
• Sulphate
• Magnesium

Should this be enough information to work with?

 

[ajdelange]

Yes. Those are the key parameters.