Mash sample, ph and time

[FunkedOut]

Looking for confirmation of my thought from those smarter than I.
I always let my mash sample sit for hours before I measure the ph.
Does this time allow for the mash sample ph to drift/change?
Or is this fine?

More details about my process:
Underlet my mash. Usually takes ~5 minutes to get ~5 gallons in.
Stir the mash well.
Cover and let sit for 20 minutes.
Draw ~2 quarts off the drain valve and pour back in the top.
(Mash tun has zero dead space and 1.5 quarts below the false bottom)
Draw my small sample (~2oz) and place in the freezer.
When the mash is done, I pull the ph sample out of the freezer and place at room temperature.

Sometimes, I'll make to back-to-back batches this way.
At the end of the day, after pitching and cleaning, I'll clean myself up and gather notes including measuring these samples ph.
For right now, I'm not adjusting the ph on the fly, as my measurements are close enough.
I'm just gathering data for future brews.
My question is more about the accuracy of my measurements.
Do these few hours of sitting around at room temp change the ph in any way?
I think not, but I know not.

Thanks in advance.

 

[Qhrumphf]

pH definitely changes over time. You want that pH reading early in your mash.

Put your sample in something small and metal (metal measuring cup works well) and ice bath it. Chills down super quickly if you stir the sample a bit.

There's also a case to be made for taking readings at mash temp as that's where the actual reactions are occurring. Would have to adjust targets from established literature which is almost all based on room temp, and accept some accelerated wear to your electrode.

Or, just chill it down fast as above.

 

[dmtaylor]

pH definitely changes over time. You want that pH reading early in your mash.

Put your sample in something small and metal (metal measuring up works well) and ice bath it. Chills down super quickly if you stir the sample a bit.

There's also a case to be made for taking readings at mash temp as that's where the actual reactions are occurring. Would have to adjust targets from established literature which is almost all based on room temp, and accept some accelerated wear to your electrode.

Or, just chill it down fast as above.

Exactly.

 

[ajdelange]

pH definitely changes over time. You want that pH reading early in your mash.

But not too early. What happens in a mash is that right at dough in the reactions between the mash liquor and the malt components aren't fully underway as it takes time and stirring for them to thoroughly intermix and react. Thus, if you have, as we often do, add acid to the water, an early pH measurement will measure the acid water to the point where you may be alarmed. Over time, in this case, the acid will penetrate the malt and the pH will rise. It typically takes 20 to 25 minutes for things to 'equilibrate' and this is the best time to get a reading though there is no reason not to get additional reading before and after the 25 minute point if you can. The pH of the brew will continuously vary over the course of the brew and it is a good idea to record pH at various points throughout the brew day as this can provide a valuable road map for subsequent brews.

 

[FunkedOut]

let's set forth a few assumptions upon which to clarify the question in the OP:

- 25 minutes into the mash, all of the chemicals in the mash will have 'equilibrated'
- a sample is drawn from the mash at that time, which is representative of the homogeneous wort
- the sample is instantly cooled to room temperature (72*F / 22*C) and maintained at that temp forever more

will measuring the ph of the sample immediately, versus measuring the sample 4 hours later yield a different result?

 

[mabrungard]

Most definitely, the pH of a mash does vary during the mash.

One observation was able to confirm recently, is that grists with a significant percentage of wheat or wheat malt take longer to stabilize than high percentage barley grists and the initial wort pH of a light colored high wheat grist tends to be markedly low...as if the acid that I had added to the water was not buffered by the grist. However after 30 to 45 minutes of mashing time, the wort pH did end up within a couple of hundedths of the targeted pH. That response had been observed in multiple past high wheat content grists and I'm now confident that its a real response. I'm guessing that wheat extract takes more time to leave the kernel and enter the liquid phase (wort).

I do see a slight variation of that sort of pH variation in barley grists, but its much quicker and the excursion from the target pH does vary higher or lower initially. I no longer measure wort pH any earlier than 15 minutes into a mash and I consistently see that later pH measurements more closely align with pH predictions and those measurements are more consistent with a steady-state reading. 30 to 45 minutes would be when I'd consider pH measurements relatively reliably indicating what your wort pH is.

 

[ajdelange]

will measuring the ph of the sample immediately, versus measuring the sample 4 hours later yield a different result?

I'd think so but if the sample were liquid, i.e. no mash solids in it, I'd expect the change to be smaller than it would be were mash solids present. Simple enough to find out next time you brew.

 

[Qhrumphf]

I always found 10-15 mins into the mash (or sampled immediately after a 30-45 min mash-in after which most of the mash has already been sitting in that 15-30 min range) gave me consistent and repeatable readings in both temp and pH. I've definitely observed the sample change over time if I've left the sample out after cooling. Perhaps I should experiment with reading a bit later in the mash.

 

[FunkedOut]

Interesting.
I can’t help but wonder, which is truly the ph of interest here:
- the ph that the mash settles at (equilibrium)
- the ph that is present during the majority of the conversion
- the ph that is present when say 80% of the conversion is complete. to set optimum conditions for that last 20% that might need more help.

I’m starting to think that having abandoned adjustments of the mash ph on the fly (just measuring to tweak future brews), perhaps the best time to draw the sample is at the end of the mash during recirculation.
Recirculation certainly helps with homogeneity, and this happens at a time when temp is no longer of concern.
I have a passive, insulated mash tun.
Draw the sample then, cool and measure immediately.

Edit: I should’ve worded that better. ph level is of interest at all times. What I should’ve written is at what time during the mash, should we choose to optimize ph level. I see this as a distributor cap, where timing is a compromise across varying conditions (phases). The EFI equivalent would be one where you could command and maintain ph levels at all times.

 

[ajdelange]

What we are looking for is something that we can measure that will help us to make good beer. I often draw the analogue to an aircraft flying above 18,000 feet. The ATC (Air Traffic Control not Automatic Temperature Compensation) system has dropped any pretense that the barometric altimeter in an aircraft can be set such that it accurately reflects the height of the aircraft above sea level and so has all pilots set their altimeters to 29.92" (1025 mB) even if they are flying over a Bermuda high. Thus if the guy's altimeter says 24,000 feet his actual altitude may be substantially different from that but the point is that another guy whose altimeter is also set to 29.92" and which says 25,000 feet is 1000 feet above the first guy even though he is not actually at 25,000'. The goal of achieving separation is met and the system works.

Thus, in brewing, we measure the pH 25 minutes in confident that if that pH falls within a certain band we will make a better beer than if it falls outside that band. We are fully cognizant that the actual pH at mash temperature 10 minutes after strike is not the pH we measure at 25 minutes at room temperature and that the pH will continue to drift, if more slowly, for hours and never really reach equilibrium. But this system allows us to be successful as brewers and so we use it.

 

[FunkedOut]

Agreed, we are taking a measurement that helps turn out good beer.

If that measurement is taken later in the mash, when the drift has slowed down, the timeliness of drawing the sample, and subsequently measuring the pH becomes less critical. This would offer a more forgiving process.
This is probably a non-issue, as stirring at 25 minutes and spending 5 minutes chilling then 5 minutes measuring is not challenging.

The moment we choose to draw the sample, is the data point we use to recalculate water chemistry for the next brew. Thus, is the moment we choose to optimize pH for.

I am curious as to what the difference would be to drawing that sample at the end of the mash. How many hundredth's off? Tenth's?

I am also curious to see how a filtered (through the grain bed) sample's pH value drifts over time.

I have a new toy (MW102) and think I found a new game to play.
Next brew I have planned contains 10% white wheat (3.2SRM).
Perhaps Martin's observations will show themselves.
Maybe I'll draw a few samples and sacrifice this batch's mash temperature to the gods of science.
Hopefully find my own "-3dB" so to speak.

Setting up to run a stability test now, thanks to your sticky, aj.

 

[ajdelange]

.
Hopefully find my own "-3dB" so to speak.

Ooops. Just gave yourself away.

 

[FunkedOut]

 

[FunkedOut]

stability test went very well. I am more than happy with these results:

calibrated, performed the stability test for 6 hours by leaving the probe in the 4.01 buffer solution for the duration, then checked the 7.01 buffer solution again.
saw an error of 0.01.

looking forward to testing some wort...

 

[FunkedOut]

Finally got a chance to brew today; always waiting on those yeasties...


Brewed a Blonde Ale today and 20 minutes into the mash, I stirred the mash well and drew a sample.
During those first 20 minutes, I got a fresh calibration on the MW102.
It took me 10 minutes to cool the sample down to 24*C (75*F) and get a pH measurement.

I was shooting for 5.42 with Brun' Water and measured 5.45.
I decided to keep measuring that sample for a while. Have a look at this graph:

The pH of the 20pH sample (sample drawn 20 minutes into the mash) kept rising for a good while.
Now, because of the stirring, and I drew the sample by dipping a cup into the top of the mash, I managed to pick up quite a bit of floating bits (grain).

I decided to measure the pH of the 1st runnings after recirculation. So this sample (75pH) was taken 75 minutes into the mash. It is a full tenth lower than what the 20pH had settled to, but about a 5 hundredths higher than the initial reading.

What would you call the pH of this mash?
I am leaning towards the 5.51-5.52 range.

 

[Silver_Is_Money]

I'm confused as to the time at which you took the '75pH' sample, as above you state that it was taken 75 minutes into the mash, but your graph indicates 135 minutes, or 75 minutes post the mash (assuming the mash to have been 60 minutes in duration).

But I'm further confused by your very first sample (with a measured 5.45 ph) which you state was taken 20 minutes into the mash, but which you plotted at the zero minute mark on your graph.

For the '20ph' sample, did you merely re-measure the pH repeatedly over time for this single sample? Did you also measure additional samples drawn within what I'm presuming was a 60 minute duration mash? Or was this actually a 120 minute mash?

Forgive my obvious confusion, but please clarify.

 

[Silver_Is_Money]

If starch tests indicate (as they often do) that enzymatic saccharification activity is found to be complete by as early as the 20 minute mark into the mash, and the alpha and beta enzymes activities are highest within a certain pH (and temperature) range, and as you observed, the pH range as measured at the time of peak enzymatic activity is noticeably different (in your case lower) from the more downstream measured pH readings, then perhaps the pH of most concern to specifically saccharification is still the pH measured at around the 20 minute mark. As once saccharification is complete, what value (aside from final pre-boil pH adjustment) is there in measuring what will likely be a different downstream pH (presumably higher for grists which are basic with respect to the target mash pH, and lower for grists which are acidic with respect to the mash pH target), even when the pH's drawn post the 40 minutes of mashing mark will be the more stable (and more technically correct) mash pH measurement?

For your Blonde Ale, I would have wished that rather than re-measuring a single sample over and over as time progressed, you would have plotted multiple of independent and freshly drawn samples at time intervals throughout the mash.

 

[ajdelange]

As you have clearly seen, mash pH is a moving target. This is because the reactions taking place in the mash take place slowly. To add to the problem pH meters take a couple of minutes to stabilize. When people first started proposing to predict mash pH I would ask "Mash pH when?" I didn't think it could really be done for several reasons and this was one. In such a situation you can only standardize your measurement procedure. Lab and brewery observations suggest that the rate of change of mash pH with time has slowed way down by about 20 minutes into the mash though it continues to change, as you have seen, beyond that. There isn't much point in waiting an hour to check on mash pH and so the very unofficial recommendation seems to be to grab the sample at 20 - 35 minutes into the mash to cool the sample as quickly as possible and to record the pH reading on the sample as soon as it is stable.

I too am confused by the times shown on the plot but assuming the reading plotted against 0 was the first reading on the 20 minute sample and that this reading was stable I would call that the pH of the mash. I am troubled by the apparent rise in pH of the cooled sample by as much as 0.1 pH so I suspect that the first reading was not stable. The points follow what I would expect to see in a sample that has been removed from the mash and allowed to cool i.e. a slight increase in pH over time as the temperature falls. Thus I suspect that the pH of your mash at 20 minutes was around 5.56.

A lowering to 5.51 - 5.52 an hour later is not surprising either. The reactions continue as long as the grain is in contact with water and keep going on even into the kettle. So, as noted above, if you as me "What should my mash pH be?" I'll answer with another question "When?"

You are really interested in the time history of pH in the mash. You want it to be in that 5.4 - 5.6 band initially (as measured 20 - 25 minutes in) and you want it to drop thereafter (or at least not to rise very much) until you get to the kettle and there you want it to drop again so that the wort entering the fermenter is in the range 5.0 - 5.2. You then want the yeast to drop it again down to 4 - 4.7. So tracking pH at various points in the brew day is wise. The value in the 20 - 25 minute measurement seems to lie in its ability to predict a successfuk brew. Get the 20 minute pH into that 5.4 - 5.6 band and other pH's along the way will probably fall into the correct ranges to insure a good beer.

 

[Silver_Is_Money]

Due to the measurement cluster that hovers around a value of 5.57 pH at roughly 30 minutes (give or take) post the initial pH sample, I'm calling the actual mash pH 5.57 for your Blonde Ale. The mash water environment was likely pre-acidified and pre-mineralized via software guidance to meet a target of 5.42 pH, and in the real world of your grist (as opposed to the idealistic world of the software, which must attempt to normalize in a world where such normality rarely exists sans when considering averages) this acidification actually under-shot the target by about 0.15 pH points. Not bad. The goal of mashing within a range of 5.2 to 5.6 pH was clearly met. And lastly, the initial 5.45 pH measurement must be presumed to have been merely an anomaly which happened purely by random chance to be right close to the initial target pH of 5.42.

I would initially presume that the actual pHDI (or DI_pH) of your primary base malt was higher than the fixed (in relation to Lovibond color) default value of the software.

 

[dmtaylor]

Finally got a chance to brew today; always waiting on those yeasties...


Brewed a Blonde Ale today and 20 minutes into the mash, I stirred the mash well and drew a sample.
During those first 20 minutes, I got a fresh calibration on the MW102.
It took me 10 minutes to cool the sample down to 24*C (75*F) and get a pH measurement.....

What would you call the pH of this mash?
I am leaning towards the 5.51-5.52 range.

Given that most people measure pH in the first 10-25 minutes of the mash, and given that your initial reading was 5.45 at about 30 minutes with no data before then, I would say your official pH of this mash was about 5.45. Also, personally, I measure only the clear stuff, not a well-mixed sample as you did. Granules of stuff probably gave false indication of raising your pH.

 

[Silver_Is_Money]

The concept of pH itself was unknown until 1909. Electrodes were first used to measure pH in 1920, and the first commercial pH meter didn't happen until 1936. How on earth did anyone brew good beer prior to the pH era?

Edit: Pure trial and error is my guess. With regional ales and lagers brewed mainly in conformance with local water characteristics.

To this day the best Bohemian Lager I ever brewed was made in the 90's using spring water, and before I had any concept of a strict requirement for mash pH. I recently had the spring water company give me the analyticals, and they are:

38 ppm Ca++
5.8 ppm Mg++
18 ppm Na+
64 ppm Cl-
14 ppm SO4--
52 ppm Alkalinity (as CaCO3)

Since I mashed a Pilsner malt straight up in water with 52 ppm alkalinity, my mash was likely in the mid 5.8 range (or perhaps higher). But it tasted spectacular. And I had several requests to repeat the batch, doing it the same way each time. It was a two step mash, with a rest at 122 degrees before bumping up to the low 150's.

Edit again: Not that I'm recommending it for anyone's actual use, but after a bit of playing around, this is about as close as I can come to re-creating the water that I mentioned above, given what I have on hand, and without spending serious time at it:

 

[FunkedOut]

Apologies on not describing that graph clearly enough,
thanks for those who took the time to follow along,
and extra special thanks to those that contributed thoughts.



This was a 75 minute mash.



20 minutes into the mash, I stirred the mash well and dipped a frozen pyrex cup into the top of the mash to collect a gritty ~150mL sample.
Let's call this the 20pH sample; the red series in the graph.

I immediately placed that cup into the freezer again.
10 minutes later, the 20pH sample was at 24*C.
I immediately measured the pH of the 20pH sample.
This measurement is plotted against t = 0 on the graph.
The x axis (time) adds time to the clock after that.

The temperature of the 20pH sample, as measured by the MW102 probe, is the blue series in the graph.

I kept the probes in the 20pH sample and recorded the values seen in the graph that belong to the red and blue series.



Now to explain the orange and green series...

At the end of the 75 minute mash, I recirculated until the wort was clear; ~10 minutes.
I immediately began to collect the first runnings in the kettle and collected a sample.
Let's call this the 75pH sample; the orange series in the graph.
The temperature of the 75pH sample, as measured by the MW102 probe, is the green series in the graph.

The reason that the first 75pH reading doesn't show up until t = 135 minutes, has to do with cooling of the sample, reading the gravity, beer, forgetting about the sparge, vorlauf again, beer, sparge, beer and beer.

At t = 135 minutes, I measured both samples (20pH and 75pH).
I did it again at t = 155 minutes.

Beer.

 

[FunkedOut]

For your Blonde Ale, I would have wished that rather than re-measuring a single sample over and over as time progressed, you would have plotted multiple of independent and freshly drawn samples at time intervals throughout the mash.

That would be a much better indicator of what was happening in the mash, agree.
Your wish, which I share, is why I drew the 75pH sample.
Only accomplishing that task to a very small degree.

This brew, I was chasing the answer to my question earlier in the thread about letting the pH sample sit until the end of the day before measuring.

 

[FunkedOut]

The mash water environment was likely pre-acidified and pre-mineralized via software guidance to meet a target of 5.42 pH, and in the real world of your grist (as opposed to the idealistic world of the software, which must attempt to normalize in a world where such normality rarely exists sans when considering averages) this acidification actually under-shot the target by about 0.15 pH points. Not bad. The goal of mashing within a range of 5.2 to 5.6 pH was clearly met.

No acid was used in the brewing of this beer.
Simple grist: 9lbs of Rahr Pale Malt, 1lb of Rahr White Wheat Malt, 0.5 lb Briess Victory Malt.
1.5qt/lb mash thickness.
1.61g of calcium sulfate, 1.59g of calcium chloride (anhydrous), 0.21g of salt.
100% distilled water.

And lastly, the initial 5.45 pH measurement must be presumed to have been merely an anomaly which happened purely by random chance to be right close to the initial target pH of 5.42.

I am not sure I am convinced of that yet. I believe the mash sample pH was actually 5.45 when that measurement was taken.
I believe the large amount of solids in the mash sample created a disproportionate ratio of water/mineral and grist, possibly facilitating the pH rise.

I am troubled by the apparent rise in pH of the cooled sample by as much as 0.1 pH so I suspect that the first reading was not stable.

Stable as a rock. I let the electrode sit in the sample for a few minutes after swirling. The reading remained unchanged for those few minutes.

I've been sick and tired of not trusting my cheap pH meter to the point that I would not make any adjustments based on the readings. That's when I knew I was wasting my time and bought this MW102. I trust it. At the end of the brew day, measured the two buffers I used to calibrate it right on.

 

[ajdelange]

Stable as a rock. I let the electrode sit in the sample for a few minutes after swirling. The reading remained unchanged for those few minutes.

Roger that with one minor amendment: move the electrode around in the solution a little. This gets fresh sample over the bulb and over the reference junction. You may see a change of 0.01 - 0.02 pH when you do this. It is known as 'stirring error' and will settle out a few seconds after you stop stirring. When the reading comes back to where it was before you stirred you know you have stable reading. There is a bit of an art in the use of a pH meter. Experience will teach it to you.

I've been sick and tired of not trusting my cheap pH meter to the point that I would not make any adjustments based on the readings. That's when I knew I was wasting my time and bought this MW102. I trust it. At the end of the brew day, measured the two buffers I used to calibrate it right on.[/QUOTE]As we used to say in the IC, "Trust but verify."

 

[ScrewyBrewer]

Given that most people measure pH in the first 10-25 minutes of the mash, and given that your initial reading was 5.45 at about 30 minutes with no data before then, I would say your official pH of this mash was about 5.45. Also, personally, I measure only the clear stuff, not a well-mixed sample as you did. Granules of stuff probably gave false indication of raising your pH.

I take mash samples 20 minutes into the mash after cooling to 77F. Before storing the meter away in storage solution I soak the bulb end in cleaning solution. After two years the pH readings begin to drift and I know its time to replace the bulb with a new one.

 

[FunkedOut]

My thoughts on this run is that the sample was not representative of the mash due to the water/mineral to grist ratio being so different.
I will do this again with the sample taken after drawing a gallon from the valve (through the grain bed and false bottom).
Drawing the sample off the bottom like that should provide a more representative sample of the mash that should be have a more stable pH.
More data is more better.

 

[Silver_Is_Money]

My thoughts on this run is that the sample was not representative of the mash due to the water/mineral to grist ratio being so different.

I think you are fretting over this too much, as to my knowledge solids should not impact a pH probes output. If you had gotten a more clear sample there would be even less grist in it. Yet (assuming good mixing) it would be a fully representative sample of the pH conditions within the developing Wort at the very time the sample was pulled.

As to solids, they make pH probes for taking readings of soil, wherein a hole is dug, some distilled water is tossed in and stirred to make a mud soup of soil and water, and then a presumably valid soil pH is read from amidst this mud mess.

 

[mabrungard]

I will do this again with the sample taken after drawing a gallon from the valve (through the grain bed and false bottom).
Drawing the sample off the bottom like that should provide a more representative sample of the mash that should be have a more stable pH.

Homogeneity and complete mixing are a necessary thing when it comes to collecting a representative sample. Every brewing chemistry calculator predicts their result based on complete mixing of the various components of the grain, water, and additives. I find that the largest discrepancy in prediction and measurement is due to non-homogeneity of the overall wort. Adding minerals and acids and then mixing the mash by hand is almost certain to be non-homogeneous (and therefore, non-representative) in places within the mash. Circulating your wort through the grain bed is a much better way to 'mix' and homogenize your wort. I strongly agree that you'll see better results by either implementing some sort of RIMS/HERMS or simply conducting a vorlauf step.

 

[FunkedOut]

I'm not so much thinking that the solids themselves interfered with the probe's measurement function.
I'm thinking that the mini mash that I created (the 20pH sample) drove itself to a different pH than the rest of the mash did.

Not really fretting. Just skeptic on a data collection of 1 brew.
I will do it again and report back here. Different grist unfortunately.
Or fortunately whether you look at the science or tap list.

 

[Silver_Is_Money]

I'm not so much thinking that the solids themselves interfered with the probe's measurement function.
I'm thinking that the mini mash that I created (the 20pH sample) drove itself to a different pH than the rest of the mash did.

You rapidly cooled it to room temperature. That should have greatly suppressed the enzymes activity level (which at 20 minutes was about done doing its appointed task anyway).

 

[FunkedOut]

Brewed an ESB today.

This time, instead of stirring 20min into the mash, I performed a vorlauf, drawing a total of ~4.5 gallons of wort and pouring over the top, ~1/2 gallon at a time.
4.5 gallons is just bout my strike volume, so this means I turned the entire wort over one time before drawing the pH sample.

Only took me 5 minutes to cool the sample, as I used two frozen cups and poured from one to the other, then placed in the freezer.

Much more stable readings this time:

Again, the first reading of the 20pH sample is given at t = 0 minutes.

My goal here was to see if letting the sample sit for hours on end before measuring would yield a different measurement than reading as soon as possible.
Looks like it will drift over time for sure.

Dismissing the first mash (Blonde Ale) and relying on the second mash (ESB),
I'd say a few minutes does not make an appreciable difference, but anything over an hour starts to drift into a non representative sample.


As an aside, I noticed that the pH meter was noticeably slower today than it was last mash.
During the calibration process, it took several minutes of swirling and resting to have the reading stabilize. I took that into account during the calibration confirmation and the wort readings.
I guess it's the exposure to the wort that make it sluggish?
It's still crazy fast to stabilize compared to the $15 specials I've worked with.

 

[FunkedOut]

A little more info on the mash...

All DI water, no minerals or acid/acid malt.
9lbs of best ale
1lb 2oz of amber
9oz of crystal 45L
9oz of crystal 77L

Brun' Water said it'd have a pH of 5.43.
No complaints here.