Decoction vs no decoction on a Dunkel

After last year's Maibock, this is the
2nd experiment where I compared a beer brewed with
decoction mashing and a beer brewed with infusion mashing.


This time I wanted to see if there is a
more pronounced flavor difference if the majority of the grist was
composed of highly kilned base malts. This is one type of grist for
which decoction mashing is still fairly common in Germany. test test test . So I chose
a basic Dunkel recipe and the brewing process is outlined after the
mash diagram for the 2 beers (click the diagram for a larger version).




Dunkel II

Dunkel III


99% Best Malz Dark Munich

1% Weyermann Carafa Special II

99% Best Malz Dark Munich

1% Weyermann Carafa Special II


Hochkurz infusion mash

63C (145F) for 30 min

hot water infusion

70C (158F) for 45 min

thin decoction boiled for 3 min

75C (167F) for 15 min

Intensified double decoction:

35C (95F) for 30 min

pulled 60% mash as decoction

slowly heated

70C (158) for 60 min (it didn't want to get iodine negative)

slowly heated

35 min decoction boil

returned decoction to main mash

63C (145F) for 40 min

pulled thin decoction; 5 min boil; returned

70C for 20 min


0.48 g/l Hallertau Magnum (12% a-acid) added before start of
boil and boiled for 60 min

0.48 g/l Hallertau Magnum (12% a-acid) added before start of
boil and boiled for 60 min


60 min; 9% boil-off

60 min; 8% boil-off


WY 2206; raised in 10l 2 Plato wort wit constant aeration

harvested from Dunkel II


pitched at 9C (48F)

fermented 8 days at 10C (50F)

pitched at 8.6 (47F)

fermented 11 days at 10C (50F)


11 days at 15C (59F)

18 days at 15C (59F)

cold conditioning

8 weeks at 1 C (34F)

4 weeks at 1C (34F)


6 weeks at 10 C (50F)

6 weeks at 10 C (50F)


OE: 12.8 Plato

attenuation limit: 71%

attenuation: 67%

attenuation delta: 4%

AE: 4.2 Plato

pH: 4.25

OE: 12.0 Plato

attenuation limit: 76%

attenuation: 69%

attenuation delta: 7%

AE: 3.7 Plato

pH: 4.28

It should be noted that the Dark Munich
malt caught me by surprise and the mash for Dunkel II resulted in a
rather unfermentable wort (attenuation limit 71%) which was
compensated for during the mash of Dunkel III (see longer maltose
rest). As a result the wort for Dunkel III was more fermentable. But
both beers finished with a similar attenuation (67% and 69%). The
poor fermentability was attibuted to the enzymatic weakness of the
Best Malz Dark Munich which took a long time to convert (see the 40
min 70C rest of the decoction) and showed similar attenuation
problems in subsequent beers.

3 ½ months after brewing Dunkel
II and 3 months after brewing Dunkel III I tasted the beers
side-by-side. It should be noted that at the time of this tasting I
was not aware that I brewed one with decoction and the other one
without. I had brewed quite a number of other beers in between and
actually forgot how I mashed these beers and thought that they were
both brewed with decoction until I checked my notes.

Dunkel II (left) and Dunkel III (right) 



Dunkel II

Dunkel III


– sweet Munich malt character

– hint of roast present

– but not as strong as Paulaner Dunkel

– same as Dunkel II


– dark mahogany color

– tan head

– slightly more hazy than Dunkel III

– slightly more head retention than Dunkel III

– same as Dunkel II

– except less haze and slightly less head retention


– malty sweet start

– finishes with dark malt character and a hint of roast

– slightly less sweet than Dunkel II in its start

– the finish is slightly less malty

– hit of roast present


– fuller than Dunkel III

– slightly less full than Dunkel II


As you can see I did notice differences
berween the beers but it is difficult to tie them to the decoction
alone. I contribute the better clarity, lower head retention and
thinner mouthfeel of the more intensely mashed Dunkel III to the
stronger protoelytic activity in the mash. Its increased sweetness
stems from the larger amount of residual fermentable sugars (see
attenuation delta) compared to Dunkel II. I even considered Dunkel II
(the non-decocted, more precisely only 3 min thin decoction boil) to
be the more malty of the two beers.


Conclusion: This experiment was
not as conclusive as the Maibock experiment and I would even call it
inconclusive. There were too many differences between the analytic
parameters (in particular the attenuation numbers) of the two beers
to tie their slight taste differences to the more intensive mashing
(including a 35 min decoction boil) of the Dunkel III. A future
experiment needs to increase the decoction boil time to 60 min and
attempt to keep the original extract, attenuation limit and
attenuation and fermentation the same.


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