Sensory and Instrumental Flavour Analysis of Wort Brewed with Dark Specialty Malts
Stefan Coghe 1, 3, Els Martens 1, Hélène D'Hollander 1,
Patrick J. Dirinck 2 and Freddy R. Delvaux 1,
1 Centre for Malting and Brewing Science, K.U. Leuven, Kasteelpark
Arenberg 22, B-3001 Leuven, Belgium.
2 Laboratory for Flavour Research, KaHo Sint-Lieven, Gebr. Desmetstraat
1, B-9000 Gent, Belgium.
3 Corresponding author. E-mail: Stefan.Coghe@agr.kuleuven.ac.be
J. Inst. Brew. 110(2), 94-103, 2004 | VIEW ARTICLE
ABSTRACT
In order to explore the flavour produced by dark specialty malts,
wort samples were brewed with different malts and evaluated by
sensory and instrumental analysis. With increasing wort colour,
a trained tasting panel detected more intense bitter and burnt
flavours, whereas sweet and husky flavour notes decreased. Conversely,
caramel and bread-like flavour attributes had a maximal
intensity for the intermediate wort colours. Tasting of 20 EBC
worts indicated that the flavour profile was significantly affected
not only by malt level and malt colour but also by malt origin.
Furthermore, the darkest caramel malt (480 EBC units) was
found to contain most Maillard aldehydes as determined by the
reaction with thiobarbituric acid. Similarly, other intermediate
products of the Maillard reaction such as acetic acid, diacetyl
and 2,3-pentanedione were found to arise in a higher concentration
in dark caramel malts (220-480 EBC units) than in
roasted malt (1200 EBC units). Dynamic headspace GC/MS
further revealed that brewing with dark specialty malts considerably
increased the level of 3-methylbutanal, its aldol condensation
product (2-isopropyl-5-methyl-2-hexenal) and heterocyclic
Maillard compounds. In contrast, dark malts drastically reduced
the amount of hexanal in wort. By means of HPLC, it was established
that only extreme roasting temperatures lead to the thermal
degradation of ferulic acid to 4-vinylguaiacol in malt.
Key words:
Maillard reaction, purge and trap GC/MS, sensory
assessment, thiobarbituric acid number, wort tasting.
Publication no. G-2004-0517-221 ©2004 The Institute & Guild of Brewing