How much effect does a ferulic acid rest have?

When reading up on brewing Weissbier (also known as Bavarian Wheat) one of the suggestions is a ferulic acid rest. This rest around 43 C
(110 F) works best at a pH > 5.7 and liberates ferulic acid into the
wort. This ferulic acid is the precursor to 4-Vinyl-Guajakol which is
responsible for the the clove flavor produced by Weissbier yeats. The
more ferulic acid there is in the wort the more 4VG should be produced
by the yeast and the more clove character the beer should have.

This
is what I wanted to test. So I brewed a Weissbier recipe twice. Once
with a simple Hochkurz mash and another one with an additional 30 min
43C rest at a pH > 5.70. For the second beer acid malt was added at
61C. This is above the optimal range for protoelytic activitry since I
also wanted to limit the protein degradation during the time the mash
spent in the 45-55C range.

The following table lists the process steps taken for the 2 beers:


 

82

Weissbier IIIa

83

Weissbier IIIb

water

70 ppm Ca, 4 ppm Mg, 10 ppm Na, 13 ppm SO4; 30 ppm Cl, 118 ppm
HCO3,

RA = 43 ppm CaCO3

70 ppm Ca, 4 ppm Mg, 13 ppm Na, 13 ppm SO4, 15 ppm Cl, 138 ppm
HCO3

grist

33.5 % Vienna Malt

64 % Pale Wheat Malt

1.5 % acid malt

34 % Vienna Malt

64% Pale Wheat Malt

2 % acid malt (added at 61C)

Mash

63C for 30 min; pH 5.57

heating 1 C/min

71C for 40 min

heating 1C/min

75C for 10 min

43C for 30 min; pH 5.77

heating at 1 C/min

63C for 20 min; pH 5.54

heating 1 C/min

71C for 40 min

heating 1C/min

75C for 10 min

Hops

0.52 g/l Hallertauer Tradition 6.8% for 60 min (added before
start of boil)

0.52 g/l Hallertauer Tradition 6.8% for 60 min (added before
start of boil)

Yeast

WY 3068; 1000 ml Kraeusen

WY 3068; 1000 ml Kraeusen

primary

7 days at 18.5 C

6 days; started at 16C and was raised to 20C over the next 3
days. Fermention seemed done after 3 days. But it was stuck at 5
Plato.

Lowered temp to 12C while WLP830 (W34/70) was prepared.

While at 12C for 10 days the gravity fell from 5.7 to 3.6
Plato. Beer was racked off old yeast, WLP830 Kraeusen was pitched
and the beer was bottled at 3.8 Plato.

Carbonated at 17C for 10 days

maturation

5 days at 10 C;

10 days at 17C for carbonation;

see primary

 

Note that the fermentation for the 2nd
batch slowed down signficantly after it reached a gravity of 6 Plato.
At this point I decided to pitch a lager yeast and I cooled the beer
for the time it took to propagate that yeast. This was to drop out most
of the original yeat and limit autolysis. This was unplanned and I hope
it is not the reason why the results of the experiment are like they
are.

 

Tonight I tasted the two beers:

 


 

82

Weissbier IIIa

83

Weissbier IIIb

age

7 ½ weeks

5 weeks

aroma

slight clove

slight banana

not much difference

slight clove

slight banana

not much difference

head retention

fairly stable

not much difference

fairly stable

not much difference

appearance

dark golden color

dark golden color

taste

sweet start that finishes with a distinct clove note which
lends the beer some bitterness

not much difference between.

The clove note seems to be at the same level.

sweet start that finishes with a distinct clove note which
lends the beer some bitterness. There seems to be a tad more other
yeast character present

otherwise not much difference

The clove note seems to be at the same level.

mouthfeel

average mouthfeel

(compare to standard German Pils)

average mouthfeel

(compare to standard German Pils)

stats

original extract: 11.75 Plato

limit of attenuation: 77%

actual attenuation: 77%

apparent extract: 2.7 Plato

pH: 4.25

original extract:12.7 Plato (I got better efficiency than expected)

limit of attenuation: 78%

actual attenuation:78%

apparent extract: 2.8 Plato

pH: 4.11

 

Conclusion: For the chosen yeast holding the ferulic acid rest
didn't make any noticeable difference in the clove flavor that was
produced during fermentation. While additional experiments should be
made to confirm these findings it is very much possible that this rest
is not worth the additional work.

(comments are disabled b/c
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