[maltster]

I've got a bock planned this weekend and after much research I'm going to do what I'm calling a "modern decoction", considering the somewhat highly-modified state of current malts.  Without going into the details, why can't I begin with two separate mashes and bring both through the same steps up through the sach rest, then maintain the largest portion of the mash at the sach temp while heating the smaller decoction portion to boiling, then add the decoct portion to the main mash to bring it to mashout temp.

In other words, avoid having to transfer hot mash from one vessel to another by starting with separate mashes from the get go.  Any input appreciated.

[tomsawyer]

Should work, I do find that I lose a lot of heat when transferring the amount out for the decoction.

[hopfenundmalz]

Ina decoction you mash in and pull the thick part and boil. This has a low water to grain ratio, the grain is where the heat bursts small starch granules. The mostly liquid part left behind has the enzymes, which would be denatured by high temps. As you propose, you might be denaturing a lot of enzymes.

But this is Homebrewing, where we can try things like you propose, because we can. Give it a try and report back on how it works. I think you will end up making beer!

[hubie]

I agree you might take a hit on efficiency because you're denaturing the enzymes in the small mash when you boil it, but you can probably get around that by draining the liquid in the small mash into your big mash before bringing the small mash to boil.

No matter how you end up doing it, you'll need to do a little experimenting to hit your target temperature.  If you don't drain the liquid from your small mash before boiling it, you could probably treat that as an infusion step when calculating how much you'll need in your small mash.  My guess is that your small mash will probably end up being fairly small because most of the thermal mass is in the water you're boiling in the small mash.  If you drain your small mash first before boiling, you might find that the amount of grain you need in your small mash to raise the temperature of your main mash is pretty big and your small might be about the same size as your big.  I know that when I do a decoction session, the amount of grain I end up pulling turns out to be a substantial part of the grain in the tun.