Side mash with wort - enough diastatic power?

[FatDragon]

I'm going to be splitting a batch as an APA and an oatmeal and buckwheat porter soon and I'm trying to figure out the best way to do it. My typical process is to mash a double grainbill as if I'm making a barleywine, then split and top off the wort at some point in the process, either pre-or post-boil, but I usually use the same grainbill for both sides of my double batches while this time I'm using two different recipes.

My thought is to take 3/4 of the base malt and a couple specialty grains that I'm comfortable using in both batches for the main mash, then doing a separate mash with 1/4 of the base malt and the porter-specific grains in a smaller pot (or a bucket if necessary for volume). The main mash would be 87% base malt, while the smaller mash would be 53% base malt, 21% oats, 13% buckwheat, and 13% roasted barley, so almost half unmalted grains.

For an APA, I mash around 66.5 C for a medium to light body. For the porter, I typically mash around 69 C for a fuller body. So I've got this interplay of mash temps and diastatic power to play with to try to achieve my goals with the oatmeal porter side of the brew. Do I do a regular lower-temp mash with the porter mini-mash to try and get as much conversion out of that 53% base malt as I can, then let the difference be my extra body? Do I mash that portion hotter and then sparge with wort from the main mash to balance things out? Do I use wort from the main mash as my mash water for the mini mash and quickly bring it up to 69 C (not worrying too much about strike temps because that would denature a lot of the enzymes in the original wort)? Do I cereal mash the adjuncts or just grind them and let the grain bag make the most of its large surface area for filtration?

There seem to be a lot of options, but I'm not sure how many roads lead to Rome and how many lead to a porter that's too sweet or too dry. Does anyone with a better head for the science side of brewing have any suggestions?

 

[Gnomebrewer]

53% base malt will most likely have enough diastatic power to convert the side mash, but it would depend what it is. Standard pale malt generally has higher DP than higher kilned English malts. English ale malts would struggle to convert, and may need a longer mash. It would help a bit if the roasted barley came out of the mini mash to be steeped separately (it doesn't need mashing).

I haven't used buckwheat, so can't comment on a cereal mash for it, but for oats, rolled oats are pre-gelatinised so no need for a cereal mash. Raw oat grains would be a different story.

It really sounds like these two beers would be best mashed separately - especially as you're going to be doing two separate mashes anyway!

 

[FatDragon]

53% base malt will most likely have enough diastatic power to convert the side mash, but it would depend what it is. Standard pale malt generally has higher DP than higher kilned English malts. English ale malts would struggle to convert, and may need a longer mash. It would help a bit if the roasted barley came out of the mini mash to be steeped separately (it doesn't need mashing).

I haven't used buckwheat, so can't comment on a cereal mash for it, but for oats, rolled oats are pre-gelatinised so no need for a cereal mash. Raw oat grains would be a different story.

It really sounds like these two beers would be best mashed separately - especially as you're going to be doing two separate mashes anyway!

It's European Vienna - either Chateau (Belgian) or Weyermann (German) - I get it from a local brewpub so I'll see what he's got on hand when the time comes.

I might look at adding the RB late in the mash or steeping post-mash, but I want all of the character it gives when added to the mash, so if I can't get that character from a steep, I'll take the potential conversion hit for my desired flavor. As for the adjuncts, I'll forego the cereal mash. I've cereal mashed with buckwheat once, but I didn't really notice any difference from just grinding it and tossing it in the mash (this was back before I had a kid so single batches were the norm).

Reading and formulating my reply to your message also jogged my brain about my original plan for this brewday. The original idea was to brew as if I were making a large batch of APA in the 34 liter kettle and a mini batch of oatmeal porter in the 11 liter stock pot, get through both boils, and then mix a third of the APA wort in with the porter wort before hopping the APA in the whirlpool. If the mini-mash is able to convert on its own, that seems like it should still be a viable strategy. Even if it converts a bit less than a typical mash, the extra unfermentable sugars should provide a bit of extra body to make up for half of the wort being mashed lower than I typically want in a porter.

 

[tennesseean_87]

It's European Vienna - either Chateau (Belgian) or Weyermann (German) - I get it from a local brewpub so I'll see what he's got on hand when the time comes.

I might look at adding the RB late in the mash or steeping post-mash, but I want all of the character it gives when added to the mash, so if I can't get that character from a steep, I'll take the potential conversion hit for my desired flavor. As for the adjuncts, I'll forego the cereal mash. I've cereal mashed with buckwheat once, but I didn't really notice any difference from just grinding it and tossing it in the mash (this was back before I had a kid so single batches were the norm).

Reading and formulating my reply to your message also jogged my brain about my original plan for this brewday. The original idea was to brew as if I were making a large batch of APA in the 34 liter kettle and a mini batch of oatmeal porter in the 11 liter stock pot, get through both boils, and then mix a third of the APA wort in with the porter wort before hopping the APA in the whirlpool. If the mini-mash is able to convert on its own, that seems like it should still be a viable strategy. Even if it converts a bit less than a typical mash, the extra unfermentable sugars should provide a bit of extra body to make up for half of the wort being mashed lower than I typically want in a porter.

Unconverted starches are not unfermentable sugars. It sounds like you'll have a hard time if using Vienna, which doesn't have the DP of plain 2-row. Maybe steep the Dark grain and crush really fine on those specialty malts, and use a different base malt? Do the separate mash at a higher temp to speed conversion and add body.

 

[FatDragon]

Unconverted starches are not unfermentable sugars. It sounds like you'll have a hard time if using Vienna, which doesn't have the DP of plain 2-row. Maybe steep the Dark grain and crush really fine on those specialty malts, and use a different base malt? Do the separate mash at a higher temp to speed conversion and add body.

I could probably sub the Vienna for Pils and add a couple hundred grams of Munich for a bit of character, or maybe just up the Vienna by about 10% for a bit of extra DP. With such a low amount of buckwheat, I'd just use the blender so it will be very fine, but I'll probably keep the flaked oats whole because a lot of sticky unmalted flour is a good way to learn what a BIAB stuck sparge looks like (ask me about the time I used 2kg of rye baking flour in the mash for a black IPA...).

It's looking like brewday will have to wait another week so I'll have a bit more time to dial in the plan before putting it into action.