Full text of DOI:10.1002/j.2050-0416.2002.tb00543.x

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R. C. Agu, D. L. Devenny, I. J. L Tillett, and G. H. Palmer
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J. Inst. Brew. 108(2), 215–220, 2002
The normal huskless barley sample (blue aleurone
layer) was a Himalayan barley (Hordeum sp) whereas the
variety Halcyon (Hordeum vulgare cv), a United Kingdom
barley variety which also has a blue aleurone layer, was
obtained from the University Brewing store and was de-
Sulphuric acid dehusked barley had a higher germinative energy
and lower microbial infection than normal huskless (naked) bar-
ley, suggesting that the pericarp layer harboured microbial infec-
tion which may have limited the germination rate. Dehusking the
normal huskless barley using sulphuric acid resulted in lower
microbial infection, and increased germinative energy. The nor-
mal huskless barley sample had a higher b-glucan content than
the acid-dehusked barley and had slower b-glucan breakdown
during malting. This resulted in the release of seven times more
b-glucan during mashing, and the production of wort of higher
viscosity. The normal huskless barley sample had a higher total
nitrogen content than the acid-dehusked barley but both samples
produced similar levels of amylolytic (a- and b-amylase) activ-
ity over the same malting period. No direct correlation was
found between barley total nitrogen level and the amylolytic
activity of the malt. When barley loses its husk at harvest, the
embryo is exposed and may be damaged. This may result in
uneven germination which can reduce malting performance and
hence malt quality.
3
husked using cold 50% H SO , as described previously .
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Media preparations. A direct plating method was em-
ployed in the investigation of barley microflora. Potato
dextrose agar (PDA, Oxoid) was prepared as described
4,14,16
elsewhere
. To assess microbial contamination, fine
forceps, sterilised between transfers by dipping in ethanol
and burning off were used to plate out eight corns equi-
distantly round the circumference of the 9 cm agar plates,
and two grains were placed towards the centre to provide
maximum spacing. The PDA plates were incubated for 7
o
14
days at 25 C .
Key words: Acid-dehusked, a-amylase, b-amylase, barley, b-
glucan, normal huskless, malting.
8
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The total nitrogen content of barley and total soluble
nitrogen content of malt wort were determined using the
Kjeldahl method using a Tecator System 2020 digester
and a Tecator Kjeltec System 1002 Distillation unit. The
titration unit was a Metrohm Herisau Multiburette E485
Malting research on different kinds of cereals has a
1
1
long tradition . This has led to a better understanding of
2
4
the malting process . Nevertheless, this understanding
pertains mainly to normal commercially cultivated barley
4
(
Hordeum vulgare), which contains an outer layer of husk
System .
material. In contrast, the malting potential of acid-
dehusked barleys has been subjected to minimal observa-
tion while that of normal huskless (naked) barley has had
even less attention. The purpose of this study was to in-
vestigate differences between normal huskless (naked) and
acid-dehusked barleys to assess the influences which acid
and normal dehusking can have on malting and microbial
properties of each type of grain. Structurally, the pericarp
layer is present in normal huskless (naked) barleys, but it
is removed by treatment with 50% sulphuric acid.
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Barley or malt were milled using the Buhler Miag mill
at setting 5. Exactly 0.5 g of barley or 1.0 g of malt was
used for the assay as described in the Megazyme mixed-
TABLE I. Properties of the normal huskless and acid-dehusked barley
samples.
Acid-
dehusked
normal
Acid-
dehusked
standard
barley
Normal
huskless
huskless
Moisture (%)
10.6
2.5
4.6
90.0
93.0
blue
ND1
ND
ND
94.0
96.0
blue
10.2
1.7
2.7
97.0
100
blue
1
The Extract Factory, Scotmalt Ltd, Kirkliston, West Lothian, Edin-
burgh, Scotland
ICBD, Heriot-Watt University, Riccarton, Edinburgh, Scotland
Corresponding author: R. C. Agu (E-mail:
2
Total nitrogen (%)
3
-
Glucan (w/w%)
2
G.E. (4ml test %)
H O test (%)
3
2
2
Reginald_Agu@hotmail.com)
Aleurone colour
1
Not determined.
Total nitrogen (d.m.).
2
3
-Glucan (as is).

2
0
linked b-glucan assay procedure . The absorbance of the
reaction mixture, blank, and standard were read at 510 nm
using a Philips PU 8730 UV/VIS Scanning spectro-
photometer attached to colour plotter. The b-glucan con-
tent of wort was determined by the Megazyme assay pro-
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a-Amylase activity of the malt was determined using
22
2
the Megazyme assay , as described elsewhere . b-Amy-
lase was similarly extracted and assayed using the Mega-
19
2
zyme procedure for this enzyme as previously described .
2
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cedure also
.
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Malts were milled using the Buhler- Miag mill at set-
Standard pilot plant malting procedure for barley. Bar-
ting 2 and mashed in the BRF mashing bath (Crisp Malt-
o
ley samples were screened, steeped and germinated in a
Seeger micro-malting plant (Seeger Machinenfabrik, Fell-
ing Ltd., Great Ryburgh, UK) at 65 C for 1 h as described
1
elsewhere .
o
bach, West Germany). Samples were steeped at 16 C by
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immersion for 8 h, followed by 16 h air-rest, followed by
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Extract was calculated from the specific gravity of the
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4 h immersion. Grain was germinated at 16 C for 5 days.
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o
filtered wort .
Samples were kilned at 50 C for 16 h and de-rooted by
hand to give the finished malt.
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Selective pilot plant malting procedure for barley. Be-
cause of the differences in germination of the normal
huskless (naked) barley in the hydrogen peroxide (H O )
Wort samples were equilibrated in a Julabo water bath
attached to a Brookfield Digital Viscometer (Cone and
o
2
2
Plate Viscometer LVDC 1 + CTE 40 spindle) at 20 C. Af-
test compared with the 4 ml test, which suggested that up
to 7% of the embryos were damaged or dead, an unusual
malting procedure was adopted. After steeping only the
chitted samples of both normal huskless and acid-de-
husked barley were separated out and allowed to germi-
nate for 4 or 5 days. The aim was to ascertain how both
barleys would behave when maximum germination was
achieved during the malting process.
ter equilibration, 1 ml of wort sample was injected twice
into the Viscometer using a syringe and the viscosity cal-
culated using a correction factor.
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Wort a-amino nitrogen was determined by a modifica-
2
7
1
tion of the Ninhydrin method as described previously .
Variations between experimental results did not exceed 5%.
PLATE 1. Barley with husk plated out on PDA plates.
FIG. 1. Alpha amylase activity of germinated barley.
PLATE 2. Dehusked barley plated out on PDA plates.
PLATE 3. Huskless barley plated out on PDA plates.

In order to investigate this further, the normal huskless
barley was also subjected to the dehusking procedure. This
resulted in an increase in germinative energy (Table I)
although full germination was not achieved. During the
dehusking process the pericarp is removed together with
the husk. When the normal huskless (naked) barley was
dehusked, only the pericarp was removed. The increase in
the germinative energy of the dehusked normal huskless
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The moisture levels of the normal huskless barley and
the sulphuric acid-dehusked barley were similar (Table
I). The total nitrogen and b-glucan content of the nor-
mal huskless barley were higher than those of the acid-
dehusked sample. Plates 1 and 3 show that the husk and
pericarp of barleys carry microbial infection. This is con-
firmed in Plate 2, because the acid-dehusked barley
samples (husk and pericarp absent) showed minimal level
of infection. Similarly, when acid-dehusked normal husk-
less barley was plated out on PDA medium, microbial
infection was minimal (results not shown). This further
confirms that microbial infection of the barley resided
mainly on the husk and pericarp. These results may be
linked to the lower germinative energies reported in Table
I for the normal huskless barley because microbial infec-
(
naked) barley would indicate, therefore, that the pericarp
contributed to the dormancy because the pericarp can in-
hibit oxygen uptake by the embryo. However, the inability
of the dehusked normal huskless barley to achieve 100%
germination might be due to embryo damage, which may
have occurred during harvesting.
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Figs. 1 and 2 show the patterns of amylolytic activity
development when the standard procedure was used to
malt the normal huskless (naked) and acid-dehusked bar-
leys. It is clear from Fig. 1 that both barley types followed
similar patterns in the development of a-amylase activity
during malting and that both developed similar levels of
the enzymes, differences in their germination potential
notwithstanding (see Table I). However, using the stan-
dard malting procedure, the normal huskless barley devel-
oped marginally more b-amylase activity than the acid-
dehusked barley (Fig. 2). In order to assess their full po-
tential for enzyme both barley types were malted using the
3
-5
tion can inhibit germination by limiting oxygen avail-
ability to the embryo
3
,5,7,8,9,10,12,13,17,18
.
FIG. 2. Beta amylase activity of germinated barley.
FIG. 4. Beta amylase development in 100% germinated normal
huskless (NH) and 100% acid-dehusked (AD) barley samples.
FIG. 3. Alpha amylase development in 100% germinated normal
huskless (NH) and 100% acid-dehusked (AD) barley samples.
FIG. 5. Pattern of beta glucan degradation in normal huskless
and acid-dehusked barley samples during malting.

selective procedure (see Methods). It is clear that when
00% germinated samples of normal huskless and acid-
high b-glucan content of barley contributes to a high re-
sidual level of b-glucan in the malt. This is important be-
cause maximum breakdown of b-glucan is essential during
the malting process as b-glucanase enzymes are virtually
1
dehusked barley were assayed, they developed higher
levels of a-amylase (Fig. 3) than when they were malted
in the standard way (Fig. 1). It is important to note that the
a-amylase levels of the 100% germinated samples of both
types of barley were similar (Figs. 1 and 3). The 100%
germinated normal huskless (naked) barley developed
marginally more b-amylase than the corresponding acid-
dehusked barley (Fig. 4).
2
6
inactive during mashing .
When the malts from the samples of normal, huskless
(naked) and acid-dehusked barleys were mashed, their
extract development increased progressively from day 2 to
day 5 (Table III). It is important to note that both types of
barley malts developed high extract yield on day 5 ger-
mination. The higher extract yield of the malt of acid-
dehusked Halcyon barley over the same period of germi-
nation could have resulted from a difference in the total
nitrogen content as well as varietal difference of both sam-
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In Table II and Fig. 5 it can be seen that in the normal,
huskless (naked) and acid-dehusked barley, b-glucan deg-
radation proceeded progressively over the germination
period. Only 85% of the b-glucan was broken down in the
normal, huskless grain by day 5 of germination compared
with 93% b-glucan breakdown in the acid-dehusked over
the same period. b-Glucan degradation was higher when
the 100% germinated samples were assessed (Fig. 6). The
6
ples (Table I). The higher residual b-glucan in the malt of
the normal huskless barley reported in Table II is further
reflected in both the higher wort viscosity and wort b-glu-
can shown in Table IV. In contrast, the acid-dehusked Hal-
cyon barley which had lower total nitrogen and b-glucan
content (Table I), had lower residual b-glucan in the malt
(
Table 2), and produced wort with lower viscosity and b-
glucan (Table 4). The b-glucan content of the wort from
the normal, huskless (naked) malt was over 7 times that of
acid-dehusked malted barley.
Although the acid-dehusked Halcyon barley malt had
an initial faster rate of FAN production up to day 2 germi-
TABLE II. Percentage content and degradation of -glucan (w/w %)
during germination for 5 days.
Normal huskless %
Break-
Acid-dehusked %
Sample
Standard
Break-
down
1
-glucan
Barley
down
barley
Barley
Day 1
Day 2
Day 3
Day 4
Day 5
4.6
3.7
2.1
1.4
0.96
0.71
0
20
54
70
79
85
2.7
0
61
82
89
92
93
1.06
0.49
0.31
0.22
0.18
FIG. 6. Beta glucan breakdown in 100% germinated normal
huskless (NH) and 100% germinated acid-dehusked (AD) barley
samples.
1
-Glucan (as is).
o
TABLE III. Extract (l /Kg) development pattern during germination for
1
5
days.
Germination
time
Normal huskless
barley
Acid-dehusked
barley
Day 1
Day 2
Day 3
Day 4
Day 5
ND
ND
236 (62)
269 (71)
277 (73)
289 (76)
294 (77)
300 (79)
309 (81)
307 (81)
1Values in brackets are percentage extract yield (d.m. ASBC).
TABLE IV. Properties of wort derived from normal huskless and acid-
dehusked malted barley.
Normal huskless
barley
Acid-dehusked
barley
Day 4
Day 5
Day 4
309
0.62
105
0.37
1.15
94
Day 5
307
0.64
104
0.39
1.15
90
o
HWE (l /Kg)
277
0.67
136
0.27
1.41
685
289
0.77
148
0.31
1.31
650
TSN (%)
FAN (mg/L)
SNR (%)
FIG. 7. Pattern of development of alpha amino nitrogen during
germination.
Viscosity (cP)
-glucan (mg/L)

nation, the malt of normal huskless barley produced more
FAN products towards the end of the germination period
1
2
3
4
. Agu, R. C. and Palmer, G. H., Enzymic breakdown of en-
dosperm of sorghum at different malting temperatures. Journal
of the Institute of Brewing, 1996, 102, 415-418.
. Agu, R. C. and Palmer, G. H., -Glucosidase activity of sor-
ghum and barley malts. Journal of the Institute of Brewing,
1997, 103, 25-29.
. Agu, R. C. and Palmer, G. H., Some relationships between the
protein nitrogen of barley and the production of amylolytic en-
zymes. Journal of the Institute of Brewing, 1998, 104, 273-276.
. Agu, R. C. and Palmer, G. H., Enzymic modification of en-
dosperm of barley and sorghum of similar total nitrogen.
Brewer’s Digest, 1998, 73, 30-36.
(
Fig. 7). This is probably because the normal huskless
barley had more total nitrogen to start with. It is, however,
interesting to note that the malt of the acid-dehusked bar-
ley produced a high level of soluble nitrogen (Table IV)
and FAN products (Fig. 7). This may be because barley
with a lower total nitrogen content may achieve a more
uniform and greater degree of modification than barley
which is higher in total nitrogen. This results in higher
6
,25,28
soluble nitrogen ratios
. With regard to the work re-
ported here, another interesting observation was found in
the relationship between total nitrogen content of barley
and level of FAN products of the malt. The normal husk-
less barley contained 30% more nitrogen than the acid-
dehusked barley (Table I). When malted for 5 days, and
mashed in a similar way, the normal huskless barley pro-
duced 30% more FAN products in the wort than the acid-
dehusked barley (Table IV). Such differences in soluble
nitrogen production were not correlated with differences
5. Agu, R. C. and Palmer, G. H., Development of micro-organisms
during the malting of sorghum. Journal of the Institute of Brew-
ing, 1999, 105, 101-106.
6
. Agu, R. C. and Palmer, G. H., The effect of nitrogen level on
the performance of malting barley varieties during germination.
Journal of the Institute of Brewing, 2001, 107, 93-98.
7. Bishop, L. R., Memorandum on barley germination. Journal of
the Institute of Brewing, 1944, 50, 166-168.
8
. Bishop, L. R. Second memorandum on barley germination.
Journal of the Institute of Brewing, 1945, 51, 215-224.
. Blum, P. H., Frederickson, B. L and Panos, G., American
Brewer, 1960 (Dec), 38.
6
in the development of amylolytic activity .
9
1
0. Blum, P. H. and Gilbert, S. G., Proceedings of the American
'
32'097-32ꢀ
Society of Brewing Chemists, 1957, p. 22.
The work reported in this study shows that the husk
and pericarp of barley are major sources of microbial
infection. The husk, in contrast to the pericarp, protects
the barley embryo from damage. The embryo of the nor-
mal huskless barley was largely exposed and may cause
great damage during harvesting. Damage of the embryo of
normal huskless barley may cause poor germination dur-
ing malting and produce malt of poor quality. Poor germi-
nation will, in turn, result in inadequate modification of
the endosperm materials and poor development of hydro-
lytic enzymes. This is evident because when the barley
samples with dormant or dead grains were malted, amy-
lolytic activity levels were reduced compared with malt
from 100% germinated barley. The lower level of amy-
lolytic enzymes developed in the barley samples, which
contained small percentages of ungerminated grains, re-
sulted in lower levels of b-amylase when the grain was
11. Brown, H. T. and Morris, G. H., Researches on the germination
of some of the Graminea, Part 1. Journal of the Chemical Soci-
ety, 1890, 57, 458-528.
1
2. Crabb, D. and Kirsop, B. H., Water sensitivity in barley I: respi-
ration studies and the influence of oxygen availability. Journal
of the Institute of Brewing, 1969, 75, 254-259.
13. Crabb, D. and Kirsop, B. H., Water sensitivity in barley II: in-
hibitors from barley embryos. Journal of the Institute of Brew-
ing, 1970, 76, 158-162.
14. Douglas, P. E. and Flannigan, B. A., Microbiological evaluation
of barley malt production. Journal of the Institute of Brewing,
1988, 94, 85-88.
15. Eagles, H. A., Bedggood, A. G., Panozzo, J. F. and Martin, P. J.,
Australian Journal of Agricultural Research, 1995, 46, 831-844.
16. Flannigan, B. and Healy, R. E., The microflora of barleys ac-
cepted and rejected for malting. Journal of the Institute of
Brewing, 1983, 89, 341-343.
1
7. Gaber, S. D. and Roberts, E. H., Water sensitivity in barley
seeds II. Association with micro-organism activity. Journal of
the Institute of Brewing, 1969, 75, 304-314.
6
,15,23
malted. As reported previously
, b-amylase develop-
18. Gilbert, S. G., Blum, P. H. and Frieden, A., The inhibition of
barley germination by steep liquor. Proceedings of American
Society of Brewing Chemists, 1954, p. 51-56.
ment is more correlated with malt modification than with
nitrogen levels alone. The higher FAN products in the
wort of the higher nitrogen (normal huskless) barley sug-
gest that there is a good correlation between barley nitro-
gen and a-amino nitrogen production. The high nitrogen
of the normal huskless barley also limited the extent of
endosperm modification of normal huskless barley, and
hence the extract recovery. The high b-glucan content of
the wort of normal huskless barley produced wort that was
more viscous.
1
9. McCleary, B. V. and Codd, R., Measurement of -amylase in
cereal flours and commercial enzyme preparations. Journal of
Cereal Science, 1989, 9, 17-33.
2
0. McCleary, B. V. and Glennie-Holmes, M., Enzymic quantifica-
tion of (1,3) (1,4)- -D-glucan in barley and malt. Journal of the
Institute of Brewing, 1985, 91, 273-276.
2
2
2
1. McCleary, B. V. and Nurthen, E. J., Measurement of (1,3) (1,4)-
-
D-glucan in malt, wort and beer. Journal of the Institute of
Brewing, 1986, 92, 168-173.
2. McCleary, B. V. and Sheehan, H., Measurement of cereal alpha-
amylase: a new assay procedure. Journal of Cereal Science,
1987, 6, 237-251.
3. Molina-Cano, J. L., Ramo, T., Ellis, R. P., Swanston, J. S., Bain,
H., Uribo-Echeverria, T. and Perez-Vendrell, A. M.,Effect of
grain composition on water uptake by malting barley:A genetic
and environmental study. Journal of the Institute of Brewing
The authors are thankful to Vicky Goodfellow, Georgina
Shepherd (Department of Biological Sciences, Heriot-Watt
University) and Craig Nicol (Department of Graphic and
Printing, Heriot-Watt University) for their technical assis-
tance. R. C. Agu would like to thank James Buchanan and
Enugu State University of Science and Technology, Nige-
ria, for their support.
1995, 101, 79-83.
2
4. Palmer, G. H., Cereals in malting and brewing. In: Cereal Sci-
ence and Technology, G. H. Palmer, Ed., Aberdeen University
Press: Aberdeen, 1989, pp. 61-242.
25. Palmer, G. H., Achieving homogeneity in malting. Proceedings

of the European Brewing Convention Congress, Cannes, IRL
Press: Oxford, 1999, pp. 323-363.
6. Palmer, G. H. and Agu, R. C., Effect of mashing temperatures
and endo- -glucanase on -glucan of malt worts. Journal of the
Institute of Brewing, 1999, 105, 233-235.
28. Swanston, J. S., Thomas, W. T. B., Powell, W., Meyer, R.,
Bringhurst, T. A., Pearson, S. Y., Brosnan, J. M. and Broadhead,
A., Assessment of spirit yield in barley breeding lines. Journal
of the Institute of Brewing, 2000, 106, 53-58.
2
27. Recommended Methods of Analysis of the Institute of Brewing,
The Institute: London, 1989.
(Manuscript accepted for publication April 2002)