Low pH responsible for thin, watery Dark Mild?

Hi,

I brewed up a Dark Mild recipe Friday Jan 15, 2016. The measured stats and recipe was as follows:

- 22L into fermentor, 31L into boil kettle, Brewhouse efficiency ~73%

2.75 kg Crisp Maris Otter (71.3%)
.5 kg Quaker Quick oats (13.0 %)
.143 kg Baird Carastan 37/40L (3.4%, remainder of what I had left over in the bag)
.200 kg Thomas Fawcett Dark Crystal I (5.2%)
.065 kg Baird 70/80 Crystal (2.6%, left over in the bag)
0.100 kg Thomas Fawcett pale chocolate (2.6%)
0.100 kg Baird chocolate (2.6%)

EKG for bittering to ~ 19 IBUs.

Mashed all ingredients together @ 157 F for 60 mins, in 11L water treated with 4g CaCl2 and 3 gCaSO4 added to mash.

Mash pH after 20 mins was 5.11 at 22C. This was measured using a Milwaulkee M102 pH meter, freshly calibrated with new 4.01 and 7.01 buffer packets.

Sorry for mixing temperature units, it's just how I roll and don't mind speaking more than one language when it comes to measurements.

Mash pH after 60 mins was 5.10 @ 22 C

Kettle pH after sparging (with soft untreated Vancouver, BC water) was 5.32 @ 20 C.

90 minute boil, hops in at 60 mins, 1 whirlfloc tablet at 5 minutes to flame out as well as 1/4 TSP white labs yeast nutrient.

Post boil pH was 5.19 @ 22 C.

OG = 1.039, 40 sec pure O2 into carboy.

Fermented at ambient 65F temperature using 1 fresh Wyeast 1469 smack pack, no starter. One of the reasons I brewed this beer was to propagate 1469 for future brews.

Kegged it up Tues Jan 26 and sampled last night, FG = 1.013, ABV ~ 3.4%.

The flavour is good, albiet a bit bland but the body is extremely thin and watery. I'm wondering if the very low mash pH is to blame for this. Could it be that beta amalayse activity was suppressed by the excessively low pH, leading to lack of dextrines in the final beer and the consequential thin and watery mouthfeel?

If my diagnosis is correct, any suggestions for re-brewing this beer to make it better would be appreciated. I'm thinking maybe one or a combination of these techniques may make a positive difference:

- Reserving the crystal and roast malts from the main mash, adding at vorlauf

- Mash altogether, same grist and process except add some baking soda to the mash to raise the pH. I could add some chalk I suppose but apparently that doesn't have any appreciable effect (or so I have read).

Thanks,

- Artichoke

Unfortunately, I have also created a batch or two of thin beer which was due to too low mashing pH. Getting below around 5.3 is inviting that sort of body destroying action. Boosting mash pH via alkalinity addition is really the only way to keep both the mash and kettle wort pH from dropping too low. Reserving the crystal and roast from the main mash protects the mash, but the kettle wort pH is going to be driven lower with those additions.

You can't really cheat mother nature. Add either baking soda or lime to boost the mashing water alkalinity as needed.

The problem I have with the low pH theory is that the reported pH numbers seem suspicious. Now I am the first to point out that mash pH predictions are flawed for a variety of reasons but Crisp Maris Otter is one of the malts I did detailed measurements on and based on those measurements and measurements on 80L crystal plus the usual assumptions and borrowings from Kai Troester I'd estimate the mash pH to be 5.36. That's probably not the right number but the fact that it is 0.25 units away from what OP measured is not so disturbing until one considers the implications of that in terms of the buffering capacity of Crisp MO. At pH 5.36 the proton deficit of the MO is 44.4 mEq and and estimating 11 for the oats gives a total of 50 which is covered by the colored malts and protons from the phytin reaction. At pH 5.11 its proton deficit doubles to 81.5 mEq as does the oats deficit (becomes 11) and the colored malts can't begin to make the extra up. The base malt requirement doubles while the ability of the colored malts to supply protons is decreased. To reach pH 5.11 I estimate 57 mEq of protons are required. It would take 5 mL of lactic acid to supply that many protons to pH 5.11. Thus I suspect that there was something wrong with the pH readings. It troubles me that the knockout pH was higher than the mash pH.

Indeed the OPs measurements may all have been dead on but they don't seem likely. First thing I'd do is recheck the meter against the stability test.

Even if the mash pH was 5.3 instead of 5.1 there is a mystery as the high sachharification temperature suggests that the wort should be dextrinous and we certainly can't say that the beer wants body supporting chloride.

Thanks guys for your insightful responses.

It certainly is possible that I have a bad probe if the predicted mash pH numbers are so far off from what I measured. As I mentioned, I did calibrate the meter before the brew session using fresh buffers, specifically the ones in the foil package. However, I did not re-measure the pH of these buffers to look for drift throughout the process. I assume that this is the easiest way to look out for probe drift, I'll do some thread searches on this.

AJ, I am no expert but I believe the trend of the measurements make sense, even if they are off. The kettle pH was observed to be higher than the mash pH after sparging, and then the pH fell by about 0.1 after the boil.

- Artichoke

artichoke said:

Thanks guys for your insightful responses.

It certainly is possible that I have a bad probe if the predicted mash pH numbers are so far off from what I measured. As I mentioned, I did calibrate the meter before the brew session using fresh buffers, specifically the ones in the foil package. However, I did not re-measure the pH of these buffers to look for drift throughout the process. I assume that this is the easiest way to look out for probe drift, I'll do some thread searches on this.

Click to expand...

Start at https://www.homebrewtalk.com/showthread.php?t=302256. A working MW102 has good stability which is one of the reasons it is accepted here. But they, as does everything else, sometimes fail. Even if you find your meter to be performing well it is good to have a baseline on its stability against which to compare it in the future.

artichoke said:

AJ, I am no expert but I believe the trend of the measurements make sense, even if they are off. The kettle pH was observed to be higher than the mash pH after sparging, and then the pH fell by about 0.1 after the boil.

Click to expand...

I suppose there may be some who would consider me an expert but I do not have a crystal ball and so can only speculate. I am assuming that when you say Vancouver water is soft you also mean it has little alkalinity. If you add water with small alkalinity to mash the pH should not increase very much. If you have the alkalinity number handy then pass it along and we can WAG how much of an increase might be expected.

artichoke said:

...and then the pH fell by about 0.1 after the boil.

Click to expand...

That's to be expected but we would also expect knockout pH to be lower than mash pH.

Again, let me emphasize that this is all speculation. When we think we smell something fishy we stick our noses in places we might not otherwise.

I'm very confident that I have a bad probe or meter at this point.

Yesterday I was brewing and re-calibrated my pH meter with fresh 7.01 and 4.01 buffers, per the manufacturer's instructions and several times throughout the day. I periodically checked to see how the meter was holding calibration. Here's the strange thing; The upper range (around 7.01) seemed to hold calibration solidly - 7.01, 6.99 hours after inital calibration but the low end of the pH range was completely off - from 4.01, 3.99, 3.91 and steadily falling over time to below 3.8.

I observed similar decreasing measurements with the various mash samples, for example 5.29 -> 5.28 -> ... 5.26 with no apparent end to stabilizing at a reasonable value. The M102 has a little hourglass that goes away when the measurement is supposedly stable, and with no hourglass displayed the numbers just kept falling over time.

So, with the observed drifting it would seem that all of my measurements using this tool are invalid and I think this adequately explains the "low pH" of the dark mild I supposedly measured. I don't understand why the higher pH range seems to have held it's stability while the bottom range but the upshot is this thing just isn't working.

As for the mild, after some more time in the keg it's actually a very nice beer. A bit thin but that's probably not unexpected given it's low 3.4% ABV and less crystal malts than I would normally use in this style.

- Artichoke.