Late Mash Additions and pH Effects

[michaeltrego]

I am brewing a RIS and plan to try the technique of late mash additions of the roast malts to reduce potential astringency. The roast malts (roasted/choc/black) make up 11.5% of the overall grain bill. The predicted mash pH without roast malts is 5.4. I planned to mash that for 60 minutes, then cap the mash with the roast malts, and mash for another 15-30 minutes. This is HERMS continuous recirculation. After mixing in the roast malts, the predicted mash pH would be 5.0. Is this too low going into the kettle?

 

[mchrispen]

In my mind yes, but curious to see your impression of how this turns out. I asked Gordon at NHC about his late additions of crystal/caramel/roasts relative to my RIMS. He adds while recirculating to mash out temperatures - exposed to mash temps for about 15 minutes plus lauter times. You might reserve a little alkali (baking soda or pickling lime) to add when you add the late malts... but I would also be sure to acidify your sparge water to below 6.0 or use RO water. The porters/stouts I have done (IMO) finish better when I mash around 5.5 - seems maltier.

11.5% of grist as roast seems high to me - some of that is unfermentable, but perhaps with the late addition it makes more sense. I haven't really gotten my head around the late additions. Have done it once, but I didn't adjust the volume for the shorter contact time - and was unhappy. So take the former with a grain of salt.

 

[michaeltrego]

Thanks Matt - yep, I'm going for Gordon's technique so perhaps I'll limit the exposure to the last 15 minutes. Sparge water is RO so that should be fine. I'm shooting for a higher percentage of roast based on the comments I've read regarding this technique needing a bit more malt to have it shine through appropriately in the end. Upping my main mash to 5.5 results in about 5.11 after the roast, so I think I'll give that a shot. Thanks for the feedback.

 

[rhys333]

Interesting. I've considered doing this. Just wondering... the mash is essentially done by the time you add the roasted malts. Will the pH drop have an effect at this late stage? Also, since the roast malts only need steeping (and not mashing), why not do this in a pot off to the side while your main mash is underway, then add the liquid at the start of the boil? I could be way off here... asking questions because I've puzzled over this myself.

 

[michaeltrego]

Yes, the mash is essentially done at the point and you are steeping the roast malt in the mash/sparge. I would rather eliminate the need for extra steeping pots, but you can certainly do it that way too. Since the conversion is complete at that point, I'm not worried about the pH of the mash, but rather the pH of the wort entering the kettle. Normally the pre-boil pH would be around 5.2-5.4 and go down to 5.0-5.2 during the boil. It's probably splitting hairs, but I just wanted to be sure that the dynamics in the kettle would still be fine. I am guessing the hot break will be increased if I enter the boil around 5.1-ish, which would be nice too.

 

[mabrungard]

Yes, the late additions will affect the wort pH. It is possible that the resulting kettle wort pH will be too low for the intended beer. While yeast ultimately set the beer pH, the starting wort pH does influence how low the beer pH ends up.

I do recommend adjusting that wort pH into a more appropriate range if you insist on using the late addition technique. I've had clients with overly low wort pH in their dark beers and they also found that the beer improved when the kettle wort pH was brought up to a more appropriate level. Sharp and acrid is not a good feature in a dark beer.

 

[michaeltrego]

I think I have it figured out, we'll see how it works tomorrow. The main mash minus the roast malts will be sitting at target 5.5 pH for 60 min. Then the roasts will be added along with pickling lime to bring it back up from 5.1 to 5.4. This will mash for 15 more minutes and then ramp to mash out and sparge. Fingers crossed...

 

[mchrispen]

Are you using a RIMS/HERMS or a static mash? If the latter, I would encourage you to fully dissolve the lime in a small amount of DI water first before adding, and a thorough mix.

 

[michaeltrego]

Are you using a RIMS/HERMS or a static mash? If the latter, I would encourage you to fully dissolve the lime in a small amount of DI water first before adding, and a thorough mix.

It's HERMS and yes, I am familiar with dealing with lime in the mash. Thanks for all the feedback everyone.