BIABrewer.info

Ok I've got a handle on this German process now to some extent so I can pass it on here.

Take your total water, split it into two parts, retain one for later addition, add one to kettle, use your grain proportions to determine approx the same water proportions.
Take your grain, split it into two parts, the first part can be up to 75% of the grain bill.

Mash in with your first part of the grain bill at 62c.
Hold at 62c for 30 minutes for first beta amylase rest.
Bring up to 72c, hold at 72c for 30 minutes for first alpha amylase rest.
Bring to boil for 15-20 minutes.
Add the rest of the water and drop temp to 62c again.
Mash in with the second portion of the grain bill.
Hold at 62c for 30 minutes for second beta amylase rest.
Raise to 72c and hold 45 minutes for second alpha amylase rest
Mash out by bringing to 78c and holding for 15 minutes.

Whole thing takes about 230 minutes.


Only problem I can see is the dropping of the temps, no guarantee you'd hit 62, and might have to wait a while. I'll ask about that on the forum.

Wouldn't you risk major tannin extraction if you have 75% of your grain bill in the 20 minute "decoction" boil?

One of the German guys is saying that he's had up to 80% in the first part, I'm just passing on something that I will soon try out myself as I was wondering how I was gonna manage to do a decoction for my pils.
There is some talk about tannins and protein extraction, but as of yet they are doing it successfully and reporting good results. I'm still reading the whole thread but so far there are a few proponents and none of them reckon there are any negatives.

They do say it's only suitable for lagered beers so it's possible you're dropping some of the tannins out with the trub in lagering? Not sure about that though.

Interesting to say the least

I've never quite got my head around this either but I believe that it is important to have your pH right if doing this. There is a little more info here.

There is also a nice simple page on the pros and cons etc. of decoction mashing here.

Thanks for taking the time to post the method Eoin. Looking forward to hearing how you go with it.

PP

Yes I believe it's a pH thing. Also, decoction was invented to overcome the limitations of poorly converted malts, but nowadays with well converted malts, even some German breweries are doing single infusion mashes. Shock horror. However decoction can give a better more malty flavour. I understand that Melanoidin malt gives a "pseudo-decocted" flavour and was developed for this very purpose.
Or maybe that's an urban myth??