Biab Decoction

[joecast]

so im mashing in another porter. about 30min in and i just scooped out about 1.5L from the bag and put it in a pot. just about to boil. probably boil for 10min and dump it back in.

from the small volume im boiling i guess i probably wont get too much out of it, but at least i'll have an idea of how hard/easy it is. and itl'll give me something to do for the next 30 min.

Recipe Specifics
----------------
Batch Size (L): 18.00 Wort Size (L): 18.00
Total Grain (kg): 5.50
Anticipated OG: 1.071 Plato: 17.26
Anticipated SRM: 22.8
Anticipated IBU: 33.5
Brewhouse Efficiency: 70 %
Wort Boil Time: 90 Minutes

Pre-Boil Amounts
----------------
Evaporation Rate: 15.00 Percent Per Hour
Pre-Boil Wort Size: 23.23 L
Pre-Boil Gravity: 1.055 SG 13.56 Plato


Grain/Extract/Sugar
% Amount Name Origin Potential SRM
-----------------------------------------------------------------------------
54.5 3.00 kg. Munich Malt Germany 1.037 8
27.3 1.50 kg. Weyermann Pilsner Germany 1.038 2
9.1 0.50 kg. Generic DME - Light Generic 1.046 8
5.5 0.30 kg. JWM Dark Crystal Australia 1.036 112
2.7 0.15 kg. Weyermann Caraaroma Germany 1.034 178
0.9 0.05 kg. Chocolate Malt Great Britain 1.034 475

Potential represented as SG per pound per gallon.

Hops
Amount Name Form Alpha IBU Boil Time
-----------------------------------------------------------------------------
14.00 g. Magnum Pellet 14.00 33.5 70 min.

Yeast
-----
WYeast 2124 Bohemian Lager

 

[Bribie G]

Sounds do-able. However although I have been doing grain brews for nearly a year now they have mostly been single infusion mash ales. I still don't get decoction mashing. I mean in post after post we are warned about the dangers of extracting tannins from grain husks, so don't let boiling water anywhere near them. Then you get an entire nation of brewers boiling batches of grain then whacking them back in the mash. :blink:

Someone please explain

 

[jonocarroll]

Sounds do-able. However although I have been doing grain brews for nearly a year now they have mostly been single infusion mash ales. I still don't get decoction mashing. I mean in post after post we are warned about the dangers of extracting tannins from grain husks, so don't let boiling water anywhere near them. Then you get an entire nation of brewers boiling batches of grain then whacking them back in the mash. :blink:

Someone please explain

This confused me for a while too - and I believe most people when they first realise the problem. The explanation I'm aware of is;

Tannin extraction is pH dependent - if you take a decent quantity of grain out for decoction (thick) then the pH doesn't change too much, and you don't get too much tannin extraction.

If you boil a thin mixture (say, mostly water, some grains) then the grains can't buffer the pH, and the tannins are released.


HTH.

 

[joecast]

the portion i boiled was quite thick and it being a dark beer pH should be low enough (darker grain makes the mash more acidic correct?).
the part that concerned me more as i was doing it was hot side aeration. not 100% sure if that is an issue pre-boil but hopefully it wasnt severe enough to cause any problems with the finished beer.

oh and add to the list of things not going to plan on brew day. gas bottle went empty as i was heating up the mash water. had to drive down to the bp to get one of those 3.8kg swap bottles $75!!! :angry:

 

[katzke]

This confused me for a while too - and I believe most people when they first realise the problem. The explanation I'm aware of is;

Tannin extraction is pH dependent - if you take a decent quantity of grain out for decoction (thick) then the pH doesn't change too much, and you don't get too much tannin extraction.

If you boil a thin mixture (say, mostly water, some grains) then the grains can't buffer the pH, and the tannins are released.


HTH.

Somebody has been reading. Good short explanation.