Author Topic: Calcium and Magnesium and their effects on mash pH  (Read 2140 times)

Online Kaiser

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Calcium and Magnesium and their effects on mash pH
« on: February 01, 2011, 09:18:05 PM »
I finally got around to test calcium and magnesium additions to the mash and how they affect the pH:

I have evaluated the effect of calcium and magnesium on the mash pH before when I investigated the pH effects of various waters (The effect of brewing water and grist composition on the pH of the mash). This time I repeated these experiments but didn't add the calcium and magnesium salts before dough-in but after dough-in. I was wondering if there is a difference or if I could repeat my observations.

The experiment set-up was fairly simple. 7 glasses were filled with 160 ml distilled water and heated in a ~75C water bath. 7 40 g samples of Rahr 2-row were weighed and milled separately with a ~0.75 mm mill gap resulting in a mash thickness of 4 l/kg. Strong calcium chloride and Magnesium sulfate solutions were prepared. The mash samples were doughed-in 3 min apart from each other. Each of the mashes had an initial mash pH of 63-64 C. 5 min after dough in different amounts of either the calcium brine or the magnesium brine were added. One mash remained unchanged. 15 min after the salt addition a sample of the mash was removed, cooled and its pH was recorded. Another sample was taken 60 min after the salt addition.

The results, along with data from previous mash experiments, are plotted in the chart below:



The first observation is that the distilled water pH for the Rahr 2-row is surprisingly low for a pale malt. I also observed this when I used this malt before. The earlieexperiment used pilsner malt which had a more typical distilled water mash pH of 5.7 and 5.8 respectively. Another observation is that magnesium is less effective than calcium in lowering the mash pH. A fact that is already known from the residual alkalinity equation where magnesium hardness is seen as half as effective in neutralizing alkalinity compared to calcium hardness.

As the calcium content increases the achieved pH drop gets smaller which suggests that the curve is approaching a saturation. However, this matters little to practical brewing since the amounts of calcium needed to drop the pH that low by far exceed the recommended amounts. At 42 mEq/kg, for example, the calcium content of the water in a 4 l/kg mash is already 212 mg/l. 50-150 mg/l is the recommended range for brewing water. In case of magnesium 40 mEq/kg mean ~110 mg/l magnesium in the mash water. This is way more than the magnesium levels commonly found in brewing water. Since magnesium is not as effective as calcium anyway it would not be a good choice for lowering the mash pH anyway. If the salts are only added to the mash water, their "flavor active" concentration can be spread over the total water volume used to brew that beer which will reduce the overall impact.

To put this in perspective ~2.1 g of gypsum (calcium sulfate) needs to be added for every kg of malt in order to drop the mash pH by 0.1 units. If we assume that for the average 12 Plato beer ~7.5 l water are needed for every kg of malt, this gypsum addition is equivalent to a water calcium increase by 65 mg/l and a sulfate increase of 155 mg/l.

For calcium chloride only 1.8 g are needed. The calcium content gets bumped by 65 mg/l (when spread over all the water even though the calcium is only added to the mash) and the chloride content gets bumped by 115 mg/l.

There is little change in between the 15 min and the 60 min pH measurement.

This write-up can also be found on my blog, which I recently moved to a new location and blog engine:

http://braukaiser.com/blog/blog/2011/02/01/calcium-and-magnesiums-effect-on-mash-ph/


Offline tomsawyer

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #1 on: February 02, 2011, 08:33:02 AM »
It'd be interesting to survey various malts to see what a base pH is as well as what sort of variation from batch to batch one might expect.  You certainly wouldn't guess that a 2-row would come in 0.3 pH units lower than a pils based on a color difference of maybe 0.5L.  Wonder whats going on there?  Also interesting that you didn't see the time dependent effect on pH that you reported earlier.  Seems like this malt may have more buffers in it that are holding the pH both steady and lower.  Possibly more phosphate?  If there are different buffering strengths in different malts, then one couldn't generalize about a pH change from a single experiment like this.  I could imagine that barley's phosphate content might vary with the content of the soil and any fertilization that would occur.  Not sure what the agricultural practices are for this grain in the US versus other countries.
Lennie
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Re: Calcium and Magnesium and their effects on mash pH
« Reply #2 on: February 02, 2011, 09:16:34 AM »
It'd be interesting to survey various malts to see what a base pH is as well as what sort of variation from batch to batch one might expect.  You certainly wouldn't guess that a 2-row would come in 0.3 pH units lower than a pils based on a color difference of maybe 0.5L.  Wonder whats going on there?
I don't know what is going on here, but I do have some data for different samples of base malts here: http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf
Figure 5 on page 4 has some data.

Quote
Also interesting that you didn't see the time dependent effect on pH that you reported earlier. 
That might be something unique to phosphoric acid. In general I have not seen too many cases where the pH changes during mashing unless a decoction mash is used.

Quote
Seems like this malt may have more buffers in it that are holding the pH both steady and lower.  Possibly more phosphate?  If there are different buffering strengths in different malts, then one couldn't generalize about a pH change from a single experiment like this.
I have not yet investigated if different malts truly have different buffer strength. If that's the case most of what I been been working on would fall apart. But I have used various different malts in different experiments and so far I have not seen a big difference. In particular Figure 9 on page 7 in the aforementioned paper shows 3 different malts and their response to acid or alkalinity.

Quote
I could imagine that barley's phosphate content might vary with the content of the soil and any fertilization that would occur.  Not sure what the agricultural practices are for this grain in the US versus other countries.
I do think that there are variations. But it all depends if the variations are strong enough to prevent us from making generalized ball-park statements.

I like to be able to give numbers, like saying that you have to add 2-2.5 g of gypsum per kg to drop the pH by 0.1. Even though that may not cover every case it should cover most cases and brewer's can use this as a guideline. Oftentimes brewers don't really know how much of a particular substance it takes to change the mash pH.

Kai


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Re: Calcium and Magnesium and their effects on mash pH
« Reply #3 on: February 02, 2011, 09:17:58 AM »
Interesting data, kai. Thanks for sharing!
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Re: Calcium and Magnesium and their effects on mash pH
« Reply #4 on: February 02, 2011, 09:24:37 AM »
After going through several different brands of base malts, I settled on Rahr as my favorite several years ago.  I wonder if the lower pH contributed to making my beers better, leading me to choose it over others?
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Re: Calcium and Magnesium and their effects on mash pH
« Reply #5 on: February 02, 2011, 09:33:52 AM »
After going through several different brands of base malts, I settled on Rahr as my favorite several years ago.  I wonder if the lower pH contributed to making my beers better, leading me to choose it over others?

I only have this one sample of Rahr base malt and cannot draw conclusions from that. But if it were the case that this base-malt has a typical DI pH of 5.5 -5.6 you can expect the mash pH for a Pale Ale (some crystal and and a residual alkalinity around 0) to be around 5.4, which is a great mash pH. If the DI pH is 5.7-5.8, like I get from the MO I have, the mash pH will be around 5.6, which is still ok, but I would prefer the 5.4.

The result could be a better beer from Rahr 2-row malt. This is similar to the regional brewing styles that developed because they worked well with the water at hand.

Kai

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #6 on: February 02, 2011, 12:29:42 PM »
Kai,  Excellent work as usual!  I see that you followed up on that question I posed regarding if pH drop was proportional with the Ca or Mg concentration.  I see that it does become somewhat asymptotic at high hardness, but those high levels are concentrations that most brewers probably would not utilize in their brewing water.  So for the most part, we can assume that pH drop with increasing hardness is fairly linear in the typical Ca and Mg concentrations we use.

The finding for the pH of the Rahr 2 Row malt in distilled water is surprising.  The drop of about 0.2 units compared to a Pils malt cannot be explained by the 1 or 2 SRM color increase of the Rahr 2 Row.  Since alkalinity is the enemy of most beer styles, I would not be surprised to find that Rahr is doing something to their malt that adds to its acidity.  That could easily be a soak or spray of an acid or allowing the malt to lacto ferment prior to drying or kilning. 

The high attenuation performance of the Rahr 2 Row has been mentioned by me in the past.  A very accomplished brewer here in Indy told me that he finds that this malt tends to attenuate very well for him, even when he raises the mash temp to reduce the attenuation.  As we know, reducing the mash pH by several tenths does have a side-effect of creating a more fermentable wort which would be evidenced by the high attenuation in the finished beer.   

It will be relatively easy to assess if this malt has an acidic surface treatment.  I suggest that you could compare the resulting pH when a quantity of uncrushed Rahr 2 Row is added to a volume of distilled water.  I would say the DI water temperature should be at room temperature so that no stewing or enzymatic reactions would occur.  Doing the same thing with a Pils malt or another Pale malt could provide a pH baseline.  I'm betting that the Rahr will produce a similar pH difference that you noted in your results above.  I know you have the titration equipment and can determine the resulting acid quantity on the Rohr malt. 

I look forward to your results.
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Offline theoman

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #7 on: February 02, 2011, 12:35:46 PM »
Wow, interesting stuff. All I know about calcium and magnesium is that they help relieve my heartburn.

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #8 on: February 02, 2011, 12:37:24 PM »
Seems like this malt may have more buffers in it that are holding the pH both steady and lower.  Possibly more phosphate?  If there are different buffering strengths in different malts, then one couldn't generalize about a pH change from a single experiment like this.  I could imagine that barley's phosphate content might vary with the content of the soil and any fertilization that would occur. 

Lennie,  I'm not too inclined to think that its an issue with buffers.  I've been having a discussion with AJ DeLange on mash phosphates and quite frankly, he's taking me to school.  His take is that the phosphate content and buffering capacity is relatively similar for most mashes.  I'd say that Kai's assumption that this is the case is relatively safe.  

I agree that Kai's results are interesting.  It sounds like someone needs to call Rahr and discuss what they are doing to this malt.
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Offline bluesman

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #9 on: February 02, 2011, 12:44:47 PM »
Interesting results Kai. It appears to me that the resultant drop in pH is quite small considering the doses given. Do you find this surprising as well?
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Re: Calcium and Magnesium and their effects on mash pH
« Reply #10 on: February 02, 2011, 06:38:38 PM »
I see that you followed up on that question I posed regarding if pH drop was proportional with the Ca or Mg concentration. 
In addition to that it was also on my to-do list of experiments I wanted to run. I did this with changing the water before and now I did it by adding salts (to be precise brines) to the mash.

Quote
or allowing the malt to lacto ferment prior to drying or kilning.

It seems that many home brewers think that acidulated malt (Sauermalz) is produced by letting it ferment. This is not the case. It’s simply sprayed with lacto fermented wort. Letting grain ferment would create all sorts of problems.   

I’ll have to check on the Rahr and why its DI water pH is so low.

Kai

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #11 on: February 03, 2011, 07:17:43 AM »
"It seems that many home brewers think that acidulated malt (Sauermalz) is produced by letting it ferment. This is not the case. It’s simply sprayed with lacto fermented wort. Letting grain ferment would create all sorts of problems."

Kai, you're right that it is now produced that way.  But in the past, it was 'fermented' by wetting and allowing the bacteria to flourish for a period of time prior to drying.  I don't know if any maltster still does it that way, but I figured I should cover myself and mention it. 
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Offline tomsawyer

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #12 on: February 03, 2011, 08:41:54 AM »
Lennie,  I'm not too inclined to think that its an issue with buffers.  I've been having a discussion with AJ DeLange on mash phosphates and quite frankly, he's taking me to school.  His take is that the phosphate content and buffering capacity is relatively similar for most mashes.  I'd say that Kai's assumption that this is the case is relatively safe.

I suppose the conclusion is that a mash needs no additional phosphate, that the malt releases adequate amounts for use by the yeast?
Lennie
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Re: Calcium and Magnesium and their effects on mash pH
« Reply #13 on: February 03, 2011, 08:58:49 AM »

I suppose the conclusion is that a mash needs no additional phosphate, that the malt releases adequate amounts for use by the yeast?

Yes, mash phosphate content is on the order of 1 percent by weight in malt.  So there is a bunch of it in wort.  I've seen measurements of phosphate in wort of over 800 mg/L (Malting and Brewing Science) and the starting brewing water had none.  After fermentation, the phosphate concentration is still in the 500 mg/L range, so the yeast and various precipitation mechanisms consumed some of it. 
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Offline TH

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Re: Calcium and Magnesium and their effects on mash pH
« Reply #14 on: May 18, 2011, 12:14:17 PM »
   

I’ll have to check on the Rahr and why its DI water pH is so low.

Kai

Did you find out anything regarding why the Rahr 2-row's DI pH was low?  Have you done any other 2-row DI pH malts for comparison?  Just curious.
TH