Assessment of Enzymatic Endosperm Modification of Malting Barley Using Individual Grain Analyses
Roberta M. de Sá 1,2 and G. H. Palmer 1
1International Centre for Brewing and Distilling, School of Life Sciences, Heriot-Watt University, Riccarton, Edinburgh, UK, EH14 4AS.
2Corresponding author. E-mail: r.marins_de_sa@hw.ac.uk
J. Inst. Brew. 110(1), 43–50, 2004 | VIEW ARTICLE
ABSTRACT
Enzymatic modification of the endosperm of malting barley is a
main feature of the malting process. Uneven enzymatic modification
of the endosperm (heterogeneity) can cause brewhouse
problems. Although there is a general correlation between endosperm
modification, beta-glucan breakdown and endo-betaglucanase
development, it is based on average results from sample
analyses and may conceal heterogeneity. The primary aim of this
work was to use individual grain analyses to investigate factors
that control endosperm modification and beta-glucan breakdown.
In terms of beta-glucan breakdown and physical modification,
the barley variety Chariot malted faster than Decanter.
However, both varieties showed similar distribution of endobeta-
glucanase in individual grains during malting. Further work
on individual grains showed that the correlation between betaglucan
breakdown and endo-beta-glucanase activity was not
significant. Surprisingly beta-glucan breakdown did not always
correlate with the physical modification of the endosperm. Both
these findings suggest that sample analyses of beta-glucan levels
and malt beta-glucanase activities are not reliable indicators of
the degrees of which malt samples are modified during malting.
Since the distribution of beta-glucan in individual grains of the
unmalted barley varieties was similar, the total beta-glucan
levels of the original barley did not determine the rate at which
beta-glucan was broken-down during malting. Although protein
studies are at a preliminary stage, the rate of protein breakdown
was not correlated with the rate at which beta-glucan was broken
down in the malting grain. It is possible that the physico-chemical
properties of endosperm storage proteins may limit the rate
of beta-glucan breakdown during malting.
Key words:
Beta-glucan, endo-beta-glucanase, enzymatic modification, homogeneity, malting barley, protein.
Publication no. G-2004-0311-219 ©2004 The Institute & Guild of Brewing