Statistical significance of mash pH estimates?

[ajdelange]

So when using 'Bicarbonate' we mash 40 grams of finely crushed grains in 100ml of RO water at 122F then taking measurements at 30, 60, 90 and 120 minutes.

Then repeating the process but this time adding 40ml of a bicarbonate solution made from 1 liter of RO water and 1 gram of Baking Soda. Correct?

Yes.

Also under consideration I think for use in acid titration is 1N (1 normal) hydrochloric or sulfuric acid.

Titrating towards desired mash pH values rather than away from them (as we do with bicarbonate) gives us more confidence in the data.

Or making a dilute Lactic acid solution from 1 cc of 88% lactic acid added to 100 mL of DI or RO water. Although AJ has made a case for not using Lactic acid but I don't remember what is was.

Standardized HCl or H2SO4 would always be my preference but that stuff is expensive. My objection to the 88% lactic is that I really don't know that it is 88%. I could always standardize it against CaCO3 but that's just more work. One can find on Amazon "100% pure anhydrous" citric acid dirt cheap. With the Voltmeter software it is trivial to compute the normality of this at any pH and thus it should serve as a suitable titrant.[/QUOTE]

 

[ajdelange]

So the readings are....

5.90 pH no bicarbonate
6.10 pH with .04g bicarbonate

...a .20 pH increase..

Which is just what I predicted for a malt with linear buffering of -40 mEq/L. Thus these data show the buffering of this malt to be close to -40. It's always nice when things work out as predicted but when it is this close one becomes suspicious - or at least guys like me do. Actually -39.0 matches these data a bit more closely than -40. So while this malt may have an unusually high DI mash pH it appears its buffering, at the DI pH, is about -39 mEq/L.

 

[ScrewyBrewer]

Which is just what I predicted for a malt with linear buffering of -40 mEq/L. Thus these data show the buffering of this malt to be close to -40. It's always nice when things work out as predicted but when it is this close one becomes suspicious - or at least guys like me do. Actually -39.0 matches these data a bit more closely than -40. So while this malt may have an unusually high DI mash pH it appears its buffering, at the DI pH, is about -39 mEq/L.

@ajdelange Now that @CodeSection has provided us with the DIpH of Briess Rye Malt and titration point a is there a further need to find titration point b or c as well?

 

[ajdelange]

Accurate modeling of a malt requires all three (or knowledge that b and c are 0 which is the same thing as knowing all three). At this point I think we have all seen that getting even a is difficult and I think that this must be compounded by the fact that very few readers here really understand what a represents let alone b and c. It would be great if someone wanted to do a complete titration of this malt but that's a lot to ask of someone who is new to all this and doesn't fully appreciate why he is doing all this scut work. Given that some people are coming to understand buffering to the point that they are using it in their spreadsheets and calculators I think it would probably be more valuable to get a measurement with acid on this malt. Now that, of course, gives us three points which means we can get a value of b though I wouldn't have a lot of confidence in it. What one wants to see is a cluster of data points all hovering close to a curve that fits them all pretty well. If he has that then he has confidence that the a, b and c that describe that curve really represent the malt.

 

[CodeSection]

....It would be great if someone wanted to do a complete titration of this malt but that's a lot to ask of someone who is new to all this and doesn't fully appreciate why he is doing all this scut work. Given that some people are coming to understand buffering to the point that they are using it in their spreadsheets and calculators I think it would probably be more valuable to get a measurement with acid on this malt....

So true AJ, so true. But how is one to learn? Obviously, I am interested in this as I would not have been following this thread or performing the tests. I believe you mentioned something in a previous post about using citric acid.?.? I only have lactic acid (88%), though I am putting a list of supplies to buy this week and could add citric acid to my list.

Hopefully, my efforts are helping....

 

[ScrewyBrewer]

What one wants to see is a cluster of data points all hovering close to a curve that fits them all pretty well. If he has that then he has confidence that the a, b and c that describe that curve really represent the malt.

Ok, it sounds like we're settling on using Citric Acid unless I'm mistaken. @ajdelange is it absolutely necessary to mash a fresh batch for each test? Would it be acceptable to do the following?

Mash an initial batch at 122F using 40g crushed grains and 100ml of RO or distilled water then 30 minutes later cool to 77F and take the first DIpH reading.

Then add TBD amount of citric acid to the initial mash and 30 minutes later cool to 77F and take the second a reading.

Obviously, I'm trying to find the most efficient way to accurately take a cluster of data points without having to repeat the entire 'mash from scratch process' for each sample.

 

[ajdelange]

Yes, I think citric acid is ostensibly the best choice. Lactic acid could be used but as I have mentioned in other posts there is the question of standardizing it. Also, given what we know at this point about this malt it would apparently take 0.027 mL to move the pH to 5.7. This might be difficult to measure out though one could use the same idea as mentioned in earlier posts i.e. dissolve 1 mL of the 88% in DI water made up to 100 mL. Then 2.7 mL of the dilution would correspond to 0.027 mL of the 88%. With the citric acid the amount required for an approximately 0.2 pH step would be 29 mg of the powder, call it 30 mg. Once again it seems that dissolving 1 gram of the acid in DI water and making up to 100 mL and then using 3 mL of the dilution might be the way to do this most conveniently.

No, unfortunately we cannot titrate malts in the same way we do ordinary titrations i.e. add an acid increment, titrate, measure, add another increment and titrate again. That's because of the long time constant of the reaction. We need to start anew with a fresh minimash for each acid increment in order to be able to predict from the data what happens 30 minutes into a real mash.

Please review https://www.homebrewtalk.com/forum/threads/malt-titration-finding-phdi-a-b-and-c.653403/ for the procedure. As I note in that post the scheme for more measurements faster that seems to work for me is to pipeline 3 or more measurements. To do that you would prepare 3 malt sample and put them in 3 beakers and also prepare three 100 mL volumes of DI water with the first containing 3 mL, the second 6 mL and the third 9 mL of the 1 gram in 100 mL citric acid solution. This means adding 3, 6 and 9 mL of the citric acid solution to a miing cylinder or volumetric flask and making each up to 100 mL. Pre-warm the malt beakers and water volumes. Then mix the first. Wait 5 minutes and mix the second, wait 5 minutes and mix the third. Thirty minutes after the first 'strike' withdraw, cool and measure the first beaker's pH. Thirty five minutes after the first strike (30 minutes after the second) measure the second pH and again at 40 min measure the 3rd. You should now 3 new pH reading at about 5.7, 5.5, and 5.3 to go with the pHdi measurement of 5.9 and the 20 mg baking soda measurement of 6.10. If you have the Voltmeter spreadsheet running (Brewingfunctions.yolasite.com) you can easily calculate the mEq contributed by the 30, 60 and 90 mg citric acid doses at each of the pH's measured and then stick those data with the pH's into the a, b, c calculator on Sheet 3.

 

[CodeSection]

Yes, I think citric acid is ostensibly the best choice. Lactic acid could be used but as I have mentioned in other posts there is the question of standardizing it. Also, given what we know at this point about this malt it would apparently take 0.027 mL to move the pH to 5.7. This might be difficult to measure out though one could use the same idea as mentioned in earlier posts i.e. dissolve 1 mL of the 88% in DI water made up to 100 mL. Then 2.7 mL of the dilution would correspond to 0.027 mL of the 88%. With the citric acid the amount required for an approximately 0.2 pH step would be 29 mg of the powder, call it 30 mg. Once again it seems that dissolving 1 gram of the acid in DI water and making up to 100 mL and then using 3 mL of the dilution might be the way to do this most conveniently.

No, unfortunately we cannot titrate malts in the same way we do ordinary titrations i.e. add an acid increment, titrate, measure, add another increment and titrate again. That's because of the long time constant of the reaction. We need to start anew with a fresh minimash for each acid increment in order to be able to predict from the data what happens 30 minutes into a real mash.

Please review https://www.homebrewtalk.com/forum/threads/malt-titration-finding-phdi-a-b-and-c.653403/ for the procedure. As I note in that post the scheme for more measurements faster that seems to work for me is to pipeline 3 or more measurements. To do that you would prepare 3 malt sample and put them in 3 beakers and also prepare three 100 mL volumes of DI water with the first containing 3 mL, the second 6 mL and the third 9 mL of the 1 gram in 100 mL citric acid solution. This means adding 3, 6 and 9 mL of the citric acid solution to a miing cylinder or volumetric flask and making each up to 100 mL. Pre-warm the malt beakers and water volumes. Then mix the first. Wait 5 minutes and mix the second, wait 5 minutes and mix the third. Thirty minutes after the first 'strike' withdraw, cool and measure the first beaker's pH. Thirty five minutes after the first strike (30 minutes after the second) measure the second pH and again at 40 min measure the 3rd. You should now 3 new pH reading at about 5.7, 5.5, and 5.3 to go with the pHdi measurement of 5.9 and the 20 mg baking soda measurement of 6.10. If you have the Voltmeter spreadsheet running (Brewingfunctions.yolasite.com) you can easily calculate the mEq contributed by the 30, 60 and 90 mg citric acid doses at each of the pH's measured and then stick those data with the pH's into the a, b, c calculator on Sheet 3.

Read the link above once....a lot of information to digest. Once I finish my next brew this week, I will devote more time in rereading above as well as the link.

A few quick questions though. In all the tests before, I obtained the samples at 30 and 60 minutes and cooled as quickly as possible to room temperature to take readings. The above link states to calibrate pH meter at 50c and to take all samples at 50c. In the above directions, it appears the samples should be cooled....to room temperature? So, cool or not cool? If cool, then calibrate pH meter to room temperature and not at 50c? Is it possible to extend the five minutes between adding each of the three samples to 10 or 15 minutes?

I'm sure after rereading, I may have more questions. In the meantime, when I buy some supplies tonight, I will buy some citric acid.

 

[ajdelange]

The procedure in the link is based on the MBAA paper which first introduced these concepts to the brewing community (I think - I've never seen it referenced elsewhere and I assume TQ would not have published the article were they aware of this having been done before). In any case I mashed at 50 ° C and measured at 50 °C because, as you have seen, the reaction doesn't take place or takes place very slowly at room temperature. But I also measured DI pH at room temperature in order to see what the temperature glide is for each malt and then adjusted pH DI to the room temperature reading as I knew that mash temperature would be measured at mash pH.

Now I don't want to be asking home brewers to subject their pH meters to 50 °C temperature so I have suggested here that the mash be allowed to sit at 50 °C for the prescribed measurement time and then be quickly cooled to room temperature for the actual pH reading. So yes, continue to cool.

You can certainly extend the period between starts to 10 or 15 minutes or really whatever you like. The motivation for making the time between strikes short is to shorten the total length of time required to get 3 data points.

 

[CodeSection]

Yes, I think citric acid is ostensibly the best choice. Lactic acid could be used but as I have mentioned in other posts there is the question of standardizing it. Also, given what we know at this point about this malt it would apparently take 0.027 mL to move the pH to 5.7. This might be difficult to measure out though one could use the same idea as mentioned in earlier posts i.e. dissolve 1 mL of the 88% in DI water made up to 100 mL. Then 2.7 mL of the dilution would correspond to 0.027 mL of the 88%. With the citric acid the amount required for an approximately 0.2 pH step would be 29 mg of the powder, call it 30 mg. Once again it seems that dissolving 1 gram of the acid in DI water and making up to 100 mL and then using 3 mL of the dilution might be the way to do this most conveniently.

... As I note in that post the scheme for more measurements faster that seems to work for me is to pipeline 3 or more measurements. To do that you would prepare 3 malt sample and put them in 3 beakers and also prepare three 100 mL volumes of DI water with the first containing 3 mL, the second 6 mL and the third 9 mL of the 1 gram in 100 mL citric acid solution. This means adding 3, 6 and 9 mL of the citric acid solution to a miing cylinder or volumetric flask and making each up to 100 mL. Pre-warm the malt beakers and water volumes. Then mix the first. Wait 5 minutes and mix the second, wait 5 minutes and mix the third. Thirty minutes after the first 'strike' withdraw, cool and measure the first beaker's pH. Thirty five minutes after the first strike (30 minutes after the second) measure the second pH and again at 40 min measure the 3rd. You should now 3 new pH reading at about 5.7, 5.5, and 5.3 to go with the pHdi measurement of 5.9 and the 20 mg baking soda measurement of 6.10. If you have the Voltmeter spreadsheet running (Brewingfunctions.yolasite.com) you can easily calculate the mEq contributed by the 30, 60 and 90 mg citric acid doses at each of the pH's measured and then stick those data with the pH's into the a, b, c calculator on Sheet 3.

I should have time this weekend to perform these tests. I bought some citric acid and since I have an AWSPro-200 (200x0.01g) scale, I could weigh out the 20mg.

This is the process how I understand it.

1. Add 1g of citric acid to 100mL, mixed well.
2. Add 3mL, 6mL, and 9mL (of the above mixture in #1) to three different mixing beakers with each beaker containing 100mL.
3. Pre-warm malt and heat the water beakers to 50c (122F).
4. Mix 3mL water and malt beakers, continue to stir, wait 10 minutes (I changed time frame); repeat the process with 6mL beaker beakers, wait 10 minutes; repeat the process with 9mL beakers.
5. 30 minutes after from first 3mL mix, cool 3mL mix ASAP to room temperature and measure pH.
6. After 10 minutes from above, cool 6mL mix ASAP to room temperature and measure pH.
7. After another 10 minutes, cool 9mL mix ASAP to room temperature and measure pH.

Is this correct? Did I miss any steps? Is it better to weigh out the citric acid and just add it to the three samples in powder form with their respective weight rather than go through the dilution process?

EDIT: Use 40g finely ground malt in each malt beaker.

 

[ajdelange]

That looks good to me.

 

[CodeSection]

I haven't forgotten about the tests. It took much longer hand grinding 120g of malt using my pepper grinder than I expected. Then I ended up having to work this past weekend. I still haven't brewed my Christmas brew that I have been trying to do the past couple of weeks due to work.

As it looks now, either this Friday or Sunday I will be able to perform the tests....as long as work doesn't interfere.

 

[CodeSection]

@ajdelange , @ScrewyBrewer , @Silver_Is_Money , I,m sorry in posting this data so late. I ended up getting the crud that was going across the country. Not once, not twice but three times with the first back in October, then on Thanksgiving, then on the day after Christmas. Each time it took three weeks to get over it and the damn cough. As you can imagine, it caused getting behind at work.

I ended up buying more beakers and stirrers. Today, I was able to complete the experiment listed above. Here is the data after 30 minutes:

40g Briess Rye Malt, 3mL: 5.68 pH @ 21.1c

40g Briess Rye Malt, 6mL: 5.49 pH @ 21.3c

40g Briess Rye Malt, 9mL: 5.27 pH @ 21.2c

 

[ScrewyBrewer]

@CodeSection glad you’re feeling better after all you’ve been through. I was wondering are you able to maintain a constant mash temperature throughout the testing? The reason I ask I’m not sure how well the crock pot I have can hold a set temperature.

 

[CodeSection]

@ScrewyBrewer , for the most part, as long as I was watching it and constantly taking the temperature, I was able to fairly maintain the temperature. Though, I was constantly taking the temperatures about every 3-4 minutes. So, at times I reduced or completely turned off the gas burner to maintain the temps.

 

[ScrewyBrewer]

Got it. It's pretty much a manual process maintaining temperature. I'll plug in the crock pot fill it halfway with water and see what happens.

 

[Silver_Is_Money]

@ajdelange , @ScrewyBrewer , @Silver_Is_Money , I,m sorry in posting this data so late. I ended up getting the crud that was going across the country. Not once, not twice but three times with the first back in October, then on Thanksgiving, then on the day after Christmas. Each time it took three weeks to get over it and the damn cough. As you can imagine, it caused getting behind at work.

I ended up buying more beakers and stirrers. Today, I was able to complete the experiment listed above. Here is the data after 30 minutes:

40g Briess Rye Malt, 3mL: 5.68 pH @ 21.1c

40g Briess Rye Malt, 6mL: 5.49 pH @ 21.3c

40g Briess Rye Malt, 9mL: 5.27 pH @ 21.2c

Nice work!

 

[dmr]

Well, last Tuesday night I finally was able to brew a Saison. I changed a couple of items in my recipe and obtained new lactic acid addition suggestions. They were:

Mash Made Easy 3.10 2.98ml
Brewer's Friend 3.07ml
BeerSmith 3 7.01ml

I choose to add 3.07ml. Below are my readings:
@15 minutes: cooled to 31.8c (89.24F) 5.48 pH
@15 minutes: cooled to 29.1c (84.38F) 5.53 pH

@30 minutes: cooled to 40.3c (120.74F) 5.52 pH
@30 minutes: cooled to 29.3c (84.74F) 5.56 pH
@30 minutes: cooled to 24.6c (76.28F) 5.56 pH

I probably did not use the correct drop downs. With that said, I used the very bottom (6th) one (-5.77 to 5.82 DI_pH). I'm guessing I probably did not input some items correctly...my target was 5.40 pH.

My recipe was:
- 16.30 RO water with 9.90g gypsum and 7.91 calcium chloride
- 14.7lbs Dingeman's Pilsner
- 2.37lbs Briess Rye Malt
- 2.10lbs Briess Aromatic Malt
- 1.20lbs Flaked Rye
- 0.63lbs Torrefied Wheat

You have some nice mash pH data here. Would you consider posting similar data (from other beers you have brewed) in the thread https://www.homebrewtalk.com/forum/threads/wanted-mash-ph-measurements.661544/ ?

Such data will help everyone sort out the prediction of mash pH in actual beer-making mash situations. Cheers!