Characterisation of Key Aroma Compounds in Two
Special Malts by Means of Aroma Extract Dilution
Analysis
Veronika Mall1, Jens Voigt2, Andreas Richter3 and Peter Schieberle4
1
German Research Center for Food Chemistry, Leibniz Institute, Freising, Germany; 2 University of Applied Sciences Trier, Trier,
Germany; 3 Weyermann Specialty Malts, Bamberg, Germany; 4 Technical University of Munich, Freising, Germany
Introduction
Malt is one of the most important ingredients for the beer production, bringing in sugars, enzymes and aroma. With the uprising trend of craft
brewing the varieties in beer flavours and the therefore used malts with special aroma characteristics are increasing steadily. In order to rate
the aroma potential of two special malts, key aroma compounds in a roasted malt and a Belgian type malt were characterised by means of
aroma extract dilution analysis (AEDA).
Isolation of Aroma-Active Compounds
injector
FID
recorder
sniffing port
etc.
malt
stepwise dilution
solvent extraction
gas chromatograph
SAFE distillation
O
O
Comparison of AEDA of Belgian Type and Roasted Malt
OH
O
O
O
O
S
2048
O
O
OH
OH
O
O
1024
O
O
O
512
O
OH
OH
OH
256
128
64
Next to high FD factors for the typical Maillard reaction products, the
rosted malt also featured thermally generated odorants, such as the
smoky 2-methoxyphenol, 3-isopropyl-2-methoxypyrazine (earthy) or
the roasty, popcorn-like 2-acetylthiazol as important aroma compounds in the AEDA. These compounds are responsible for a more
smoky and earthy aroma profile. In comparison, the Belgian type malt
showed a more seasoning, caramel, malty and honey-like profile.
32
16
8
4
900
1100
1300
1500
1700
1900
RI (FFAP)
2100
2300
2500
2700
Identification was carried out by gas chromatographic and mass
spectrometric methods, in comparison with reference compounds. Crucial
identification parameters: retention index (on 2 columns of different
polarity), odour quality and intensity, and mass spectral data (MS-EI, MSCI).
Following this approach, a total of 34 aroma compounds with FD
factors ranging from 8 to 2048 were detected. The highest FD
factor of 2048 was assigned to the caramel-like 4-hydroxy-2,5dimethyl-3(2H)-furanone and 3-hydroxy-2-methyl-4(4H)-pyranone
(maltol), the seasoning like furanones, 3-hydroxy-4,5-dimethyl2(5H)-furanone (sotolon) and 5-ethyl-3-hydroxy-4-methyl-2(5H)furanone (abhexon), all deriving from Maillard reactions. Other
i4mportant
compounds
smoky, clovewere characterized as
like
2.5
the vanilla-like vanillin
flowery, honey2
vanilla-like
like
and
the
Strecker
1.5
aldehyde 3-(methylthio)1
0.5
seasoning
earthy
propanal
(cooked
0
potato-like).
The characteristic 2- and
caramel-like
roasty
3-methylbutanal
with
their
malty
aroma
fatty
malty
reached an FD factor of
512.
roasted malt
Belgian type
odorant
4-hydroxy-2,5-dimethyl-3(2H)-furanone
vanillin
3-hydroxy-2-methyl-4(4H)-pyranone
3-hydroxy-4,5-dimethyl-2(5H)-furanone
3-(methylthio)propanal
5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone
octanoic acid
phenylacetic acid
3-methylbutanal
2-methylbutanal
2-methoxyphenol
acetic acid
2- and 3-methylbutanoic acid
2-ethyl-3,5-dimethylpyrazine
(E,E)-2,4-nonadienal
2-acetylthiazol
3-isopropyl-2-methoxypyrazine
unknown compound
4-allyl-2-methoxyphenol
odor description
caramel-like
vanilla-like
caramel-like
seasoning
cooked potato-like
seasoning
musty
honey-like
malty
malty
smoky, sweet
sour, vinegar-like
sweaty, cheese-like
earthy
fatty
popcorn-like, roasty
earthy, pea-like
roasted
clove-like, smoky
FD factor
Belgian
roasted
type malt
malt
2048
2048
2048
2048
2048
1024
2048
1024
2048
512
2048
256
1024
512
512
256
512
2
512
2
64
2048
256
1024
256
1024
4
1024
4
1024
2
1024
<1
1024
<1
1024
<1
512
In general, different malting processings result in distinguishable
aroma profiles and varying sets of key aroma compounds, which can
lead to special aroma notes in beers brewed with these malts.
However, quantitative data and the calculation of odor activity values
will be necessary to map the whole potential of the special malt as
aroma influencing ingredient to special beers.
[1] Schieberle, Hofmann, In: Food Flavors. - Chemical, Sensory and Technological Properties, 2011, 411-437
© Copyright by Deutsche Forschungsanstalt für Lebensmittelchemie
Outcomes from AEDA of Belgian Type Malt
FD factor
Deutsche Forschungsanstalt für Lebensmittelchemie │ Leibniz-Institut
For an appropriate identification and characterisation of odorant compounds, the concept of molecular sensory science has been developed in our group in the
last decades [1]. After solvent extraction of the malt, the volatile compounds were gently separated from non-volatile malt components by means of solventassisted flavour evaporation (SAFE) distillation. The resulting aroma distillate was then subjected to gas chromatography-olfactometry (GC-O) to locate the
aroma active compounds. AEDA was performed to rate their importance.