Russian Imperial Stout Water Chemistry

[Fordzilla]

Hello,

This is my second venture with adjusting my water profile to obtain proper mash pH and flavor profile. I was hoping some of you guys with more info could look this over and let me know if I'm on the right track.

I am planning to steep the Roasted Barley and Chocolate Malt in the boil kettle, to avoid them throwing off my mash pH. I've never done this before, since I've never calculated my pH before. I believe that is pretty common practice for this reason, right?

Thanks!

 

[ajdelange]

If you proceed in this way the mash pH will be about the same as the base malt pH. IOW if you use a base malt with DI pH of 5.6 your mash pH will be about 5.6 and if, conversely, you use a base malt with DI pH of 5.8 your mash pH will be about 5.8. Probably higher than you want in either case but 5.6 might be OK.

Thus you will need some, at least, of the acids from the roast grains. How much depends on the particular roast grains (their DI mash pH's and buffering capacities) and on the bsae malt.

Dark beers are tough because whether you need acid or not depends on the grains so much and they are quite variable. Doubtless the best way to handle them is with test mashes in which a small amount (a pound or so) of the blended grist is mashed with warm liquor and the pH checked. Dark grain amounts can be adjusted for correct pH or, if it is desired to have a fixed amount of dark grain for flavor or color, bases or acids added as necessary for correct mash pH.

 

[Fordzilla]

Sorry AJ but I'm a little unclear on the pH. With the adjustments in the pictures above (8.43 mL lactic acid and 5g gypsum), the calculator I used came out to 5.3 pH. Is that incorrect?

In addition to the grains above I will also be using 1.7 lb of 300 Lovibond Roasted Barley and 0.9 lb of Chocolate malt.

 

[ajdelange]

I wasn't clear as to what this calculator was telling me. In any case without the lactic acid the mash pH's would be about what I put in #2. Adding 8.43 ml of lactic acid would drop each of those pH's by about 0.3 so if you are using basse malt with a DI pH of 5.6 and buffering of about 35 mEq/kg-pH then you would get around 5.3 for mash pH but if you are using a base malt with DI mash pH of 5.7 your mash pH will be about 5.4 and so on. Whether the answer is correct or not depends on whether the malt meets the DI mash pH and buffering numbers. "2 Row" and a color value don't really tell us much about the malt.

But let's suppose your malt does have characteristics that get it to 5.3 and that that is acceptable to you. You have added 111 meq of extra acidity to make up for the fact that you are leaving the roast grains out. But then you put the roast grains back in. They still contain acid and that acid will still drop the pH. Assuming the buffering of the wort to be about the same as the buffering of the mash that will result in another drop of 0.3 pH which would probably drop kettle pH under 5. You would probably want to neutralize this (with bicarbonate or lime).

Why not just mash with the roast stuff and forget the lactic acid? Given your roast grains add up to less than 10% of the grist it is likely that your mash pH would be, given water alkalinity of 90, just about right. I get estimates of 5.37 using a base malt with DI pH of 5.86 and 5.29 with a base malt with DI pH of 5.62 (these are malts I have measured but they won't be the same as yours). Clearly a test mash is the way to go here.

 

[mabrungard]

Adding the roast grain at the end of the mash does help keep the mash pH from falling too low when your mashing water doesn't have enough alkalinity. However, your water has plenty of alkalinity and the roast grains are welcome additions to the mash. The thing that this delayed roast technique does not prevent is for the wort pH from falling too low in the kettle. That can have a negative effect on the beer for some styles.

With your water, you would be better served with including the roast grain in the mash and evaluating the water treatment requirements from that point of view. The whole delayed roast thing can be a viable technique for those that don't have enough alkalinity in their water, but it is NOT a magic bullet. Most dark beer styles benefit from a slightly elevated mash and kettle wort pH and this technique does not provide it.

 

[ajdelange]

I am planning to steep the Roasted Barley and Chocolate Malt in the boil kettle, to avoid them throwing off my mash pH. I've never done this before, since I've never calculated my pH before. I believe that is pretty common practice for this reason, right?

We got wrapped up in the details of the pH so this question never really got answered. It is a fairly common practice among respected home brewers (e.g. Gordon Strong advocates it) but not for pH control so much as to avoid the harsh flavors that, in his opinion, come from holding roast malt at temperature for an extended period. He invites comparison with coffee in an office carafe which has sat out overnight and notes that if the roast grains are added at the last minute (i.e. at the end of the mash or steeped in the boil) that only the desired flavors are extracted besides which roast grains don't undergo any conversion in the mash tun. I don't personally subscribe to this theory but don't really brew anything using these grains except for the occasional Irish Stout. My thinking is that if your use of these grains is balanced and especially with the availability of the Carafa's that this shouldn't be a problem but when Gordon speaks, I listen.

 

[Fordzilla]

Thanks for the replies, guys. So I gather that each malt has it's own pH and the calculator is just guessing based upon the category ("base malt", "roasted malt", "crystal malt")? Good to know.

Using the calculator, I get 5.46 pH with my roasted malts, which isn't too far off from AJ's estimate. So I guess with my water I am OK with no mash additions, and I can skip the steeping. Thanks for the info on why to steep. I've never really experienced any harsh flavors from mashing with these grains either, but I will keep it in mind in the future if I run into that issue.

 

[ajdelange]

Thanks for the replies, guys. So I gather that each malt has it's own pH and the calculator is just guessing based upon the category ("base malt", "roasted malt", "crystal malt")? Good to know.

Each malt has it's own DI mash pH and buffering characteristics (how much the pH changes from the DI mash pH given that a unit amount of acid or base is added to a DI water mash. These are the basic data necessary to calculate the pH of a mixture of malt, water, acids and bases. The data are best obtained by measurement of the particular malt in question but this is a laborious process if done right. Some spreadsheets/calculators WAG these data based on simpler measurements, some attempt to WAG these parameters based on malt colors and in some cases, apparently, beer color. Some, apparently, are completely based on empirical observation. In any case, even where the model is robust, as in my calculations, the underlying data are not (unless the malts happen to be one of the few I've measured) and these pH estimates tend to be iffy though still useful in many cases.

Using the calculator, I get 5.46 pH with my roasted malts, which isn't too far off from AJ's estimate. So I guess with my water I am OK with no mash additions, and I can skip the steeping.

Empirical observations (mine and several others in this forum) suggest that with your water and your grain selections you should be (and that your pH will fall right around 5.5 but this is not guaranteed.