5 Step Mash

Hello,

I was trying to play with various mash profiles and I ran over the 5 step authentic German mash

Name Description Step Temperature Step Time
Acid Rest Add 12.91 gal of water at 97.1 F 95.0 F 45 min
Protein Rest Decoct 3.43 gal of mash and boil it  122.0 F 60 min
Saccharification Decoct 4.30 gal of mash and boil it  148.0 F 15 min
Saccharification Decoct 1.86 gal of mash and boil it  156.0 F 15 min
Mash Out Heat to 168.0 F over 10 min 168.0 F 10 min


Can anyone tell me what "decoct x.yz of mash and boil it" means ? Does I mean that I have to extract 3.43 gal and move it the the BK ? I looked at the step and doesn't say anything about adding water so I assume I need to take it out.

Thanks

Hi
  The decoction steps are where you take a portion of the mash out of the mash tun and boil it in a separate vessel:
  http://beersmith.com/blog/2008/09/01/decoction-mashing-for-beer-recipes/

Brad