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Mashing the Perfect Sweet Stout

2010 April 15
tags: ,
by Mad Alchemist

Creating the perfect water profile and mash for a sweet stout is an exercise in contradiction. You want the beer to be very dark, sweet, malty, and full-bodied. It should have some roasted and toasty notes without astringency. To me, that translates to the following information concerning the mash and water profile: Keep the pH of the mash fairly high, around 5.6 (at room temperature). Keep the Chloride to Sulfate ratio high, around 3 to 1. Ensure Chloride and Sodium are both above 100, but below 150. Keep the temperature of the mash up around 158°F. It also means a thicker mash of around 1.25 quarts of water per pound of grain.

Where does the contradiction come in? Mostly with the grain bill. You’re looking at 10-15% of your grist being dark, roasted malt, which will drive the pH of the mash down significantly. It’s quite difficult to get a pH of more than 5.2-5.3 (at room temperature) without ending up with too much of something in the final beer (like sodium or bicarbonates). The reason I want to keep the pH up in the 5.4-5.6 range is because I use diastatically weak base malts for sweet stouts (like Munich or Maris Otter), and it’s better for enzymatic activity in that range. It’s also theoretically going to favor alpha amylase in this higher range, while beta amylase is favored a bit lower. Favoring alpha amylase is the same reason I keep the mash temperature up high at around 158°F.

The higher the Chloride to Sulfate ratio, the more malty the final beer is going to be. You need about 100ppm of Chloride before it has significant impact, and the same generally goes for Sodium (which rounds out the beer at that level, and I find that desirable in a sweet stout). You also, of course, need at least 50ppm of Calcium. The problem with the Calcium is that it lowers pH, but you really don’t want too much Bicarbonate in beer (some people believe it creates undesirable flavors, even though a lot of it will precipitate out, so I err on the side of caution here).

Okay, I think that’s enough of the reasoning behind the numbers I aim for with a sweet stout. On to the solution(s).

The first solution I came up with was to only worry about pH during the mash, and add all of the other minerals to the water after the mash. So, I’d add Sodium Bicarbonate and/or Calcium Carbonate during the mash to raise pH, then Calcium Chloride and Magnesium (or Calcium) Sulfate after the mash. Truthfully, this seemed to work out pretty well (and A.J. deLange corroborated), but I believe there is a better, and easier, way.

Don’t mash your roasted-and-kilned grains (e.g. chocolate and black malts). Roasted grains will drive the pH down considerably, so it’s difficult to keep the pH high no matter what fancy solution you use during the mash. Roasted grains have the wonderful benefit of not needing to be mashed. So, the best solution, in my opinion, is to mash everything except for your roasted grains in your MLT, and steep your roasted grains in a separate vessel (below 170 F) simultaneously at around 2 quarts per pound. Then, combine the wort created by the roasted grains with the mashed wort in the brew kettle.

If you don’t want to steep the grains, you can essentially brew a coffee with the dark grains with either a more traditional method (heat) or you can cold brew it overnight to really avoid the astringency as much as possible… it’ll just take longer. If you cold brew, you should probably bring the temperature of the concoction to 170 F after removing the grain to pasteurize it.

Then, you can add the coffee-like brew whenever you want (start of the boil, end of the boil, directly in the fermentation vessel, even just before bottling). All will impart different character, so experiment!

Note that you might not get full extraction from all roasted grains when steeping. According to some experiments run by John Palmer, it looks like Black Patent and Roasted Barley are some of the only roasted malts that have the same yield as mashing when steeped. As such, you might only exclude those from your sweet stout mash, or you can increase the amount of other grains accordingly (e.g. multiply the ounces of Chocolate Malt you use by ~1.5-1.6 to make up for the difference).

I would not recommend sparging with the roasted wort, in part because you’re going to impact the sparge pH pretty significantly, and in part because you’re going to leave some of your flavors behind.

Hitting the ideal concentrations of all ions in the brewing water as well as the ideal pH is very easy when you leave out your roasted malts (and any other malts that don’t need to be mashed, such as caramel/crystal). By steeping the roasted malts (and, optionally, your crystal malts) separate from the mash, you might end up with a much better sweet stout in the end. As someone commented, you could also steep the grains in a bag while you transfer to the boil kettle from your MLT, which sounds like a great idea.

18 Responses leave one →
  1. Eric permalink
    March 7, 2011

    Great writeup. I’ve had two dumper batches of sweet stout (about 15% roasted barley), and I’m positive it’s a water chemistry issue now.

    I was thinking of just adding the roasted barley right before runoff so I don’t tie up another vessel (or maybe steep in a bag in the wort during runoffs).

    Your thoughts?

  2. January 7, 2012

    It sounds like a great idea to steep your dark grains in a bag in your brew kettle while you transfer from the MLT. Assuming you give it enough time, it should give you as much flavor as you’re looking for without tying up a separate vessel.

  3. April 20, 2012

    a question: what is the recomended temperature to steep de dark malts? (below 170 F, is not high?)
    thanks a lot!

  4. April 23, 2012

    If you’re steeping the dark grains hot, I’d do it at 150 F. The range for steeping grains is generally 150-170 F, but I’d stay on the low end to avoid extracting astringent tannins from the dark grains as much as possible.

  5. major permalink
    November 18, 2012

    I am glad I stumbled on this while second guessing my sweet stout plan. I will make use of the wisdom. But my concern is that I’m trying to keep my Final Gravity high without making drain cleaner. Too little conversion and too much adjucts scare me. I’m even considering some distilled water to “starve” my yeast.

  6. kraw permalink
    July 30, 2015

    Really appreciated this post in preparation for an upcoming milk stout. One question, though:

    How can the Chloride: Sulfate ratio be 3:1 while keeping both in a range of 100-150 ppm?

  7. October 22, 2015

    To get that ratio, you have to start from distilled or reverse osmosis water. It’s not super important to hit the exact ratio though; 2:1 would suffice.

  8. Ryan permalink
    December 19, 2016

    Would it also work to mash your base malts first with the appropriate water treatments, then, after mashing is complete, add the roasted malts to the top of the MLT with additional mash water? Then sparge under 170?

  9. justin Carrol permalink
    June 22, 2017

    I have a similar question to Kraw, even after your response.

    You said: Keep the Chloride to Sulfate ratio high, around 3 to 1. Ensure Chloride and Sodium are both above 100, but below 150.

    Then you said: 2:1 would suffice

    If you had Chloride at 150 and sulfate at 100 you wouldn’t even be able to achieve 2:1, right? Or am I missing something?

  10. July 10, 2017

    RE: Adding roasted malts to the mash tun during sparge

    It would probably work, but it would extend the process quite a bit since it takes time to extract everything from the malts. It’s a lot easier just to do them separately. You’d also be screwing with the pH or water profile quite a bit in the process.

  11. July 10, 2017

    RE: Chloride/Sulfate ratio to Justin Carrol

    Think you’re mixing up Sulfate/Sodium.

    I keep Sulfate right around 50 for sweet stouts, Sodium right around 100, and Chloride right around 150. 2:1 does suffice for Chloride:Sulfate depending on the recipe.

  12. Scott permalink
    July 31, 2017

    If you’re using RO water and not mashing the dark grains, how do you keep your PH down with the Sodium so high and the Chloride and Sulfate so low? Using Ez water and putting those mineral numbers in, my PH would be around 5.85.

  13. July 31, 2017

    I usually build a profile for my dark grain mash that is separate from the normal grains. I’ll measure it later on and sometimes adjust if things seem to be thrown too far off. I try to use salts if I can keep a proper balance and never go too high, but I’ll use lactic acid (lower pH) or pickling lime (raise pH) if necessary. Water is a whole can o’ worms that takes a lot of research and repetition to start getting right.

  14. Scott permalink
    July 31, 2017

    Is it possible to just add the baking soda (for the sodium) directly to the boil kettle? That way I get the benefit of the sodium, without messing up the mash PH. I’m planning on cold steeping my roasted barley and chocolate malt.

    Thanks for the quick reply btw.

  15. July 31, 2017

    Yep, you can add salts whenever you feel like it as long as you account for the potential changes. I add them in the boil sometimes, but never once I’ve transferred for fermentation.

  16. Karl Thunder Axe permalink
    August 30, 2017

    Given the lengths that you’re going to to try to drive down the bitterness of the beer, I wonder if you’d consider leaving the hops out entirely. Since their primary (or even sole) purpose is to add bitterness, adding them in in any quantity seems a little like shooting yourself in the food. Or are their preservative properties, or some other properties they contribute important enough that their presence is absolutely necessary?

  17. July 27, 2018

    We’re not trying to drive out bitterness, we’re reducing astringency and tannin extraction. Hops are necessary for proper balance.

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