The Impact of Kilning on Enzymatic Activity
of Buckwheat Malt
Blaise Patricia Nic Phiarais 1,2, Hilde Henny Wijngaard 1,2 and Elke Karin Arendt 1,3
ABSTRACT
J. Inst. Brew. 111(3), 290–298, 2005
This study investigated the impact of kilning on ␣-amylase, ␤amylase (total and soluble), ␤-glucanase and protease activities
in buckwheat malt. Common buckwheat (Fagopyrum esculentum) was steeped at 10°C for 12 h, germinated at 15°C for 4
days and kilned at 40°C for 48 h. Moisture content and enzymatic activities were determined throughout the kilning period.
Results showed moisture content was reduced from 44% to 5%
after 48 h of kilning at 40°C. ␤-Amylase was found to exist in a
soluble and latent form in buckwheat. Maximum activity of (a)
␣-amylase, (b) total ␤-amylase, (c) soluble ␤-amylase, (d) ␤glucanase and (e) protease activity occurred after (a) 8, (b) 7, (c)
30, (d) 0, and (e) 8 h of kilning, respectively. The final malt exhibited very little ␤-glucanase and cellulase activity. Proteolytic
activity was low in buckwheat malt when compared to the barley
malt control. All enzymatic activities were found to decrease
during the kilning stage. Results indicated that after prolonged
kilning at 40°C, inactivation of hydrolytic enzymes occurred;
two-stage kilning for shorter periods is recommended. Although,
amylolytic activity was low in malted buckwheat, buckwheat
malt shows potential as an ingredient for the brewing and cereal
industry.
Key words: Buckwheat, enzyme activity, free amino nitrogen
(FAN), kilning, malting, total nitrogen (TN), total soluble nitrogen (TSN).
INTRODUCTION
Buckwheat is classed as a pseudocereal because it
forms an integral part of the Polygonaceae family, while
barley is classed as a cereal as it belongs to the Poaceae
family. Seeds of pseudocereals resemble cereals in structure, chemistry and edibility 3. Buckwheat has the potential to be used as a raw material for the production of gluten free beer 26. Since there are no glutein-like proteins in
buckwheat, it is considered gluten free and can be consumed by those who suffer from coeliac disease 2,13. Coeliac disease is a food induced immunological disease of
the upper small intestine and results from gluten ingestion
in genetically susceptible individuals 2,38. The true incidence of coeliac sufferers worldwide will increase in future because of a heightened awareness of coeliac disease
1 Department
of Food and Nutritional Sciences, National University
of Ireland, University College Cork, College Road, Cork, Ireland.
2 Bio Transfer Unit, National University of Ireland, University College Cork, College Road, Cork, Ireland.
3 Corresponding author. E-mail: [email protected]
Publication no. G-2005-1108-310
© 2005 The Institute of Brewing & Distilling
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and more advanced serological tests 12. Buckwheat contains compounds, that are claimed to have a positive effect
on health such as antioxidants, which have an antihypertensive effect 37,38. It contains large amounts of soluble and
insoluble dietary fibre(s) which have a positive effect on
constipation and obesity conditions 24. Buckwheat protein
has a high biological value as it contains one of the highest amino acid scores of protein and plant stuffs37.
There are three types of buckwheat: cymosum (wild),
tartaricum (tartary) and esculentum (common) 3. Fagopyrum esculentum is the most economically important
species, making up approximately 90% of the world production of buckwheat 28. Almost all of the buckwheat plant
can be utilized for a variety of applications. The buckwheat flower is used as an excellent honey source, the
hull is used for the filling of pillows and the grain is used
as a basic material for a wide range of products e.g. pancakes and pasta 6. Buckwheat can also be used to make
malt 39.
Barley is a monocotyledonic plant and buckwheat is a
dicotyledonic plant. This leads to a different location of
reserve compounds in the kernels 20. Due to this botanical
difference, enzyme production and therefore the malting
process may differ between buckwheat and barley. In a
recent study, the effect of germination temperature on ␣amylase, ␤-amylase and protease activity in buckwheat
was determined 39. It was found that both ␣-amylase and
␤-amylase activities were low in malted buckwheat in
comparison to malted barley. The maximum activity level
of ␣-amylase was 47.8 units g–1 (wet wt) in buckwheat
without hull, which was germinated at 16.5°C. In addition,
maximum apparent fermentability (56%) was reached
when buckwheat was germinated at 20.2°C. This study
analyses the impact of kilning on moisture content and
enzymatic activity, specifically ␣-amylase, ␤-amylase (total and soluble), ␤-glucanase and protease activity during
the malting of buckwheat. Enzyme levels of buckwheat
were compared to those of barley and sorghum.
MATERIALS AND METHODS
Unmalted buckwheat
Common buckwheat (Fagopyrum esculentum) was
used in the malting trials. The buckwheat samples were
obtained from Trouw B. V. (Rotterdam, The Netherlands).
Malting procedure
The malting trials were carried out in duplicate (n = 2).
In every trial 4 × 2 kg buckwheat was malted in a micro
malting machine (Joe White Malting Systems, Perth, Aus-
Fig. 1. Means of moisture percentages (%) of buckwheat against kilning time (h).
Fig. 2. Rate of drying (%) in buckwheat against kilning time (h).
tralia). In every trial steeping, germination and kilning
conditions were kept constant: steeping (12 h /10°C), germination (96 h /15°C) and kilning (48 h /40°C). For all
enzyme analysis, rootlets were removed.
Analytical procedures
Analytical procedures were carried out in duplicate (n
= 2) and the means of all results were calculated. All concentrations were based on dry weight, unless mentioned
otherwise.
Freeze-drying
Throughout the kilning period, samples were collected
and immediately frozen in a –80°C freezer for a minimum
of 24 h. Freeze-drying (AMSCO, Finn Aqua, Lyvovac
GT2, Germany) was carried out at <45°C and <0.01 mbar
on open petri dishes.
Moisture content of malts
After drying for 24 h at 50°C, EBC-method 4.2 was
followed 10.
Friability
Friability was determined by following EBC-method
4.15 10.
␣-Amylase activity
To measure ␣-amylase activity the ICC standard
method 303 18 was followed using a Megazyme enzyme
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291
Fig. 3. Means and standard deviations of total ␤-amylase activity (〫), soluble ␤-amylase activity (䡲) and insoluble ␤-amylase activity (䊱) (U g–1) in buckwheat against kilning time (h).
kit (Megazyme, Bray, Ireland). One unit of ␣-amylase
activity is defined as the amount of enzyme required to
release 1 µmol of ␳-nitrophenol from non-reducing-end
blocked ␳-nitrophenol maltoheptaoside (BPNPG7) in 1
min under the defined assay conditions as mentioned in
the assay procedure.
Total and soluble ␤-amylase activity
␤-Amylase activities of unmalted and malted buckwheat were determined using the method described by the
␤-amylase Megazyme enzyme kit. One unit of ␤-amylase
activity is defined as the amount of enzyme required to
release 1 µmol of ␳-nitrophenol from ␳-nitrophenyl-␣-Dmaltopentaose (PNPG5) in 1 min.
␤-Glucanase activity
␤-Glucanase activities of unmalted and malted buckwheat were determined using the method described in the
␤-glucanase Megazyme enzyme kit 18.
Protease activity
The protease activity level was measured according to
the method of Brijs et al.8.
Mashing
Malted samples were mashed according to the EBCmethod 4.5.110.
Wort analysis
EBC 10-methods 3.3.2 and 4.3.2 were used to determine
the TN level in flour of unmalted and malted samples,
respectively. EBC-method 8.9.2 was used to determine
TSN in wort. A nitrogen analyzer (LECO type FP-528;
LECO, St. Joseph, MI, USA) was employed for nitrogen
determination. FAN in congress wort was measured according to method of EBC 8.10. Extract (%) of resulting
wort was measured using a Servo-Chem Automatic Beer
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Analyzer (SCABA) (Tecator AB, Sweden) according to
EBC-method 9.2.2. Wort viscosity was measured using a
falling ball viscometer at 20°C (Haake, Germany) according to EBC-method 8.4. Colour was determined in accordance with EBC-method 8.5. Fermentability was determined as described in EBC-method 8.6.1. The mash was
filtered according to EBC-method 4.5.1, through filter
paper (Schleicher & Schnell, Germany) into graduated
cylinders. The time taken for each wort sample to filter
was recorded.
RESULTS AND DISCUSSION
Moisture content
The effect of time on moisture content during buckwheat kilning is outlined in Fig. 1. The temperature during kilning was kept constant at 40°C. In the first hour,
the moisture content of buckwheat decreased from 43.9%
to 43.1%. During the free drying stage of kilning 7, the
moisture content decreased from 43.1% to 19.2% in buckwheat malt after 6 h of kilning. As the intermediate stage
of kilning begins, the rate of drying begins to slow down
due to the physically or chemically bound nature of the
residual moisture, which restricts evaporation (Fig. 2). In
buckwheat, similar results were obtained to those of barley malt kilning 32 where the rate of drying and the moisture content decreased from 19.3% to 10.5% after 12 h of
kilning. The final stage of barley malt kilning is characterised by the removal of firmly bound water in the grain.
The water content is reduced from 10% to 5%. This stage
is referred to as the bound water stage. To achieve the
removal of the bound water in barley malt, the ‘air-on’
temperature is increased to 65–75°C 7. Results showed
that in buckwheat malt the rate of drying slowed and the
moisture content decreased from 10.5% to a final moisture content of 5% after 48 h of kilning at 40°C.
Wijngaard et al.39 found that barley, which has larger
grains than buckwheat, takes up moisture more slowly
Table I. Means of parameters of malted barley, unmalted and malted buckwheat.
Parameter
Alpha-amylase activity (units g–1)
Beta-amylase (total) activity (units g–1)
Beta-amylase (soluble) activity (units g–1)
Protease activity (mg leucine h–1 g–1)
Beta-glucanase activity (units kg–1)
TNb (%)
TSNd (%)
Filterability
Extract (%)
FANe (mg L–1)
Fermentability (%)
Friability (%)
Viscosity (mPas)
pH
Colour (EBC)
Unmalted
buckwheat
Buckwheat
green malt
Buckwheat
kilned at 40°C
Barley
malt
0.1
5.3
4.8
3.7
27.0
2.2
na
na
na
na
na
na
na
na
na
35.6
23.1
13.8
4.8
56.7
na
na
na
na
na
na
na
na
na
na
19.9
24.7
21.3
5.5
17.9
1.9
0.04
good
69.2
107
61.8
91.8
1.9
6.3
3.8
105.9 cf
514.0 cf
na a
9.3 cf
537.3
1.4 c
0.06 c
good
79.9 c
106.7 c
82.7 c
96.3 c
1.5 c
6.0 c
3.0 c
a na
= not applicable.
= total nitrogen.
c Wijngaard et al.39,40.
d TSN = total soluble nitrogen.
e FAN = free amino nitrogen.
f Wet weight.
g Barley malt kilned using standard barley kilning regime (50°C–80°C).
b TN
than buckwheat; this is most likely due to the covering
layers present in the barley kernel, which may limit water
uptake during steeping 14, therefore it was expected that
buckwheat would dry faster than barley during kilning.
However Schuster and Grünewald 32 found that the moisture content in barley was reduced from approximately
43% to 11% barley in the first 9 hours of kilning at 40°C.
In contrast, the moisture content in buckwheat was reduced from 43.9% to approximately 15.5% under the
same conditions. One reason for this may be due to the
uptake of more free water because of the presence of extra
outer layers or husks around the barley kernel 31. This water is not bound to endosperm components so therefore
water is removed more easily by the kilning process.
Total ␤-amylase activity
␤-Amylase is a heat labile enzyme 23 present in unmalted barley in a bound form (linked via disulphide
bridges), a free form and a latent form 11. During malting
proteolytic enzymes cleave the disulphide bridges, solubilising the bound ␤-amylase 16. In order to determine the
amount of total and soluble ␤-amylase activity, cysteine
was used to free the bound enzyme. Fig. 3 shows results
for total, soluble and insoluble ␤-amylase levels throughout the kilning process. The determined total and soluble
␤-amylase activity levels of the unmalted and malted
buckwheat are highlighted in Table I. The insoluble levels
were calculated by subtracting the soluble levels from the
total levels. Temperature and duration of kilning were
found to influence amylase activity in sorghum malts 27.
Fig. 3 shows that in the first 7 h of kilning, total ␤-amylase activity level in buckwheat malt increased from 23.1
units g–1 to 28.1 units g–1. This confirms the findings of
Okungbowa et al.30, where it was noted that when kilning
sorghum at lower temperatures, i.e. 40°C, the enzyme
denaturing phase is avoided and increased enzyme development is observed. In addition, possible proteolytic activation of ␤-amylase zymogens during the enzymatic
phase of malt kilning may in part account for the increase
in total ␤-amylase activity 11,22,30. Over the following 41 h
total ␤-amylase activity decreased from 28.1 units g–1 to
26.4 units g–1. One reason is that when germinated grain is
kilned, a fraction of ␤-amylase activity is inactivated due
to the thermolability of the enzyme, even at these low
temperatures 11. In contrast, barley produces no extra ␤amylase during kilning, and Wijngaard et al.39 found a
significant decrease in ␤-amylase activity during malting.
Table I shows the difference in total ␤-amylase activity determined between unmalted and malted buckwheat.
This represents an additional total ␤-amylase activity produced during germination. This confirms the findings of
Wijngaard et al.39. Unmalted and malted buckwheat were
found to contain a total ␤-amylase activity level of 5.3
units g–1 and 24.7 units g–1 respectively, whereas malted
barley contained a total activity of 514 units g–1. The ␤amylase content of buckwheat malt is low compared to
that of barley malt and is better compared to sorghum
malt 1.
Fig. 4 depicts the relative enzymatic activity of total
and soluble ␤-amylase during the kilning stage of malting
buckwheat. Table II underlines the relative enzymatic activity of ␤-amylase at the end of germination and at the
end of kilning. Results show approximately 90% more
total ␤-amylase activity than in green malt. In contrast,
approximately 40% less ␤-amylase was present at the end
of barley kilning 21. Therefore it can be concluded that
buckwheat ␤-amylase is tolerant to 40°C for 48 h.
Soluble and insoluble ␤-amylase activity
Results show, that in the first 8 h of kilning, soluble
␤-amylase activity level increased from 13.8 units g–1 to
24.6 units g–1 (Fig. 3). One reason is that the total ␤-amylase activity may increase as a result of enzymatic development and proteolytic activation, which leads to an increase in soluble ␤-amylase activity. Over the period of
16 h, soluble ␤-amylase activity decreased from 23.2
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Fig. 4. Relative enzyme activity of total ␤-amylase activity (●), soluble ␤-amylase activity (䊱), ␣-amylase activity (〫), protease activity (䡲) and ␤-glucanase activity (×).
units g–1 to 20.2 units g–1. This supports the findings of
Evans et al.11, where the soluble form is less resistant to
heat denaturation and thus leads to a decrease in enzymatic activity. Our results show over the final 24 h of kilning, there is an increase of activity from 20.2 units g–1 to
24.6 units g–1 which correlates with increasing protease
activity levels where proteolytic enzymes cleave the disulphide bridges, making the bound ␤-amylase more soluble
and resulting in an increase in soluble ␤-amylase activity 16. There is also some evidence to suggest that by kilning at lower moisture contents, towards the end of kilning, enzymes become more resistant to heat 9. As soluble
␤-amylase activity increases, insoluble ␤-amylase activity
decreases accordingly.
Table I depicts soluble ␤-amylase activity in unmalted,
green and malted buckwheat. Soluble ␤-amylase activity
is the active ␤-amylase activity of the grain, therefore it is
a more important parameter than total ␤-amylase activity 39. The results of this study reveal that soluble ␤-amylase activity increased from 4.8 units g–1 to 21.3 units g–1.
Although some of the bound ␤-amylase is released during
germination either by a disulfide reductase or by a proteolytic enzyme(s)33, the results of this study reveal that most
of the ␤-amylase activity is released during kilning. The
soluble ␤-amylase activity at the end of germination was
found to be 13.8 units g–1. Therefore optimising the kilning conditions seems to enhance soluble ␤-amylase activities in malted buckwheat.
␣-Amylase activity
Fig. 5 outlines the changes in ␣-amylase activity during the kilning stage of buckwheat. Results show that ␣amylase activity increased from 35.6 units g–1 at the end
of germination to 40.3 units g–1 after the first 8 h of kilning, confirming the findings of Uriyo and Eigel 36, where
results indicated sorghum ␣-amylase was stable during
drying times of 5–10 h at low temperatures. The increase
in enzymatic activity could be attributed to continued germination during drying at low temperatures 5. Our results
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show over the subsequent 40 h of kilning, ␣-amylase activity decreased from 40.3 units g–1 to 21.4 units g–1. This
supports the finding that, after 10 h of drying, enzymatic
activity in sorghum kilning was found to decrease due to
heat denaturation 36. This is referred to as the enzymeinactivating phase of the kilning process 25. Unlike barley
amylases, where ␣-amylase is more thermostable than ␤amylase 21, ␣ and ␤-amylase in buckwheat were found to
have similar thermostability. They both show an increase
in inactivation after 7–8 h of kilning due to heat denaturation.
Like unmalted barley, unmalted buckwheat contains
very little ␣-amylase activity. The production of ␣-amylase is induced during germination 39. The ␣-amylase activity level of malted buckwheat is shown in Table I. The
buckwheat malt was found to have a final activity level of
19.9 units g–1 which is much lower when compared to
malted barley, which was found to have a value of 105.9
units g–1. Sorghum ␣-amylase activity was also higher
than in buckwheat 39. ␣- and ␤-Amylase behave similarly
in buckwheat kilning, therefore when optimising the kilning conditions, they should be considered together.
Fig. 4 depicts the relative enzymatic activity of ␣-amylase during the kilning stage of malting buckwheat. Enzymes are associated with high molecular weight proteins 21. As a result of heating during kilning, the structures
of proteins are changed to some extent and they become
denatured. Table II highlights the relative enzymatic activity of ␣-amylase at the end of germination and at the end
Table II. Relative enzymatic activities of buckwheat malt kilned at 40°C
for 48 h.
Parameter
Alpha-amylase activity
Beta-amylase (total) activity
Beta-amylase (soluble) activity
Protease activity
Beta-glucanase activity
Buckwheat
green malt
Buckwheat malt
kilned at 40°C
100
100
100
100
100
60.2
191.1
178.5
119.5
33.9
Fig. 5. Means and standard deviations of ␣-amylase activity (U g–1) in buckwheat against kilning time (h).
Fig. 6. Means and standard deviations of ␤-glucanase activity (U kg–1) in buckwheat against kilning time (h).
of kilning. Results show that at the end of kilning there is
approximately 40% less ␣-amylase activity than in the
green malt. In contrast, approximately 15% more ␣-amylase activity was present at the end of barley kilning 19.
Our results show that buckwheat ␣-amylase is more heatlabile than barley ␣-amylase.
␤-Glucanase activity
There are three ␤-glucanases, endo-␤-1,3:1,4 glucanases, (which hydrolyze ␤-1-4 links adjacent to ␤-1-3
links), endo-␤-1-3 glucanase and exo-␤-1-4 glucanase.
These enzymes together hydrolyze ␤-glucans to mainly
cellobiose or laminarobiose 23. Fig. 6 outlines the changes
in ␤-glucanase activity during the kilning stage of buckwheat. The results in this study show a decrease in ␤-glucanase activity from 56.7 units kg–1 to 48.8 units kg–1 over
the first 4 h of kilning. This confirms the findings of
Georg-Kraemer et al.15, where results indicate barley ␤glucanase is highly susceptible to thermal inactivation
depending on the grain variety. Over the final 43 h of kilning, buckwheat ␤-glucanase activity level decreased from
53 units kg–1 to 19.2 units kg–1. This compares to results
found by Uriyo and Eigel 36, where it was noted that ␤glucanase activity in sorghum decreased after 5 h of drying, possibly due to the thermolability of the enzyme 4.
The determined ␤-glucanase levels of the unmalted,
green and malted buckwheat are shown in Table I. Although ␤-glucanase activity (with an activity level of 56.7
units kg–1 present at the end of germination) decreased
during drying, part of the initial activity present in the
green malt (mean 17.9 units kg–1 ) was retained in the finished malt. This activity level is much lower when compared to malted barley, which was found to have a value
of 537.3 units kg–1. A possible explanation for this may be
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Fig. 7. Means and standard deviations of protease activity (mg of leucine h–1 g–1) in buckwheat against kilning
time (h).
due to the observation that buckwheat contains no high
molecular weight ␤-glucan 39, therefore buckwheat has
little use for the enzyme ␤-glucanase. However the small
amount of ␤-glucanase present may also be used to hydrolyze hemicellulose that may be present in buckwheat. The
method used to determine ␤-glucanase activity does not
distinguish between ␤-glucanase and cellulase activity.
Analysis of the relative enzymatic activity of ␤-glucanase activity at the end of germination and again at the
end of kilning clearly demonstrated that there is approximately 65% less ␤-glucanase activity present in the final
buckwheat malt than in the green malt (Table II). This
correlates well with data on barley malt 21.
Protease activity
A variety of endo- and exo-proteases have been identified in barley green malt 19,29. In this study, the protease
activity level was measured with haemoglobin as a substrate, which gives an indication of the total proteolytic
activity level of the grains. Fig. 7 highlights the changes
in protease activity during the kilning of buckwheat. Results show a decrease from a proteolytic activity level of
4.8 mg of leucine h–1 g–1 to 4.5 mg of leucine h–1 g–1 over
the first 3 h of kilning. This correlates with the findings of
Dickson and Shands 9, where a reduction in proteolytic
activity in barley malt was observed in the first few hours
of drying at 45°C. This reduction may be due to protease
(endo-peptidase) enzymes being inactivated during kilning, since malt endo-peptidases are relatively heat labile
and easily inactivated during kilning 23. An increase from a
proteolytic activity level of 4.5 mg of leucine h–1 g–1 to 6.5
mg of leucine h–1 g–1 over the following 4 h (3–7 h) of
buckwheat kilning was observed. This increase can be
explained by the beginning of proteolysis initiated by a
slight temperature rise within the grain bed. According to
Taylor and Boyd 35, proteolysis occurs optimally at 43°C
to 50°C in sorghum malts. Alternatively, the increase may
be due to the presence of exo-peptidases. According to
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Lewis and Young 23, exo-peptidases tolerate the heat of
kilning because they are heat stable and persist in the endosperm after kilning.
Results indicate, that over the following 21 h (7–28 h)
of kilning, a decrease in a proteolytic activity level of 6.5
mg of leucine h–1 g–1 to 5.2 mg of leucine h–1 g–1 was observed, which may again be due to the inactivation of the
heat labile endo-peptidases 23. Over the following 2 h (28–
30 h) an increase in the proteolytic activity level of 5.2 mg
of leucine h–1 g–1 to 6.4 mg of leucine h–1 g–1 was observed.
This increase may be due to the further release of amylolytic and proteolytic enzymes when kilning at such a low
temperature 36. Over the final 18 h (30–48 h), a decrease in
proteolytic activity of 6.4 mg of leucine h–1 g–1 to 5.8 mg
of leucine h–1 g–1 was observed. This correlates to the findings of Dickson and Shands 9, where results indicate little
or no further decrease was observed towards the end of
barley malt kilning.
Unmalted buckwheat contained a protease activity level
of 3.7 mg of leucine h–1 g–1 (Table I), this compares favourably to the results found by Wijngaard et al.39. Protease activity was found to increase when buckwheat was
malted. Kilned buckwheat was found to contain a proteolytic activity level of 5.5 mg of leucine h–1 g–1. Most of the
protease was synthesised during germination 39 while the
remainder of protease was activated during kilning. The
buckwheat green malt was found to have a proteolytic activity level of 4.8 mg of leucine h–1 g–1. Barley malt contains an activity level of 9.3 mg of leucine h–1 g–1 which is
almost twice the level found in buckwheat malt. Approximately 19% more protease was found in final malt than in
green malt (Table II). This correlates well with similar
results for barley malt 21. Buckwheat is a friable grain because its endosperm only contains 35% protein, whereas
80–90% of the protein is embedded in the endosperm of
the barley endosperm. Therefore protease activity is probably not as important in buckwheat malt as it is in barley
malt.
Congress mashing
Congress mashing is an essential part of routine malt
analysis. Table I highlights the parameters which were
determined during congress mashing. Buckwheat wort
colour was found to be darker than barley wort. This is
most likely because buckwheat is a much darker grain
than barley 28. Friability was found to be 91.8%. Malt friability indicates the degree to which the endosperm has
been broken down (modified). This modification occurs
during germination and therefore kilning treatment usually has little impact on malt friability. The pH of the wort
was found to be 6.3. Better brewhouse performance, wort
composition, beer flavour and stability correlate with a
lower mash pH 34, therefore adjustment of pH may be necessary for better production. Filterability of the buckwheat
wort was found to be good and correlates well with its
viscosity. The wort exhibited a viscosity value of 1.9,
which according to the EBC is within the recommended
viscosity range. Results also demonstrated buckwheat
wort had an extract level of 69.2%.
Fermentability
A healthy fermentation requires sufficient levels of fermentable sugars as well as adequate levels of assimilable
nitrogenous compound 17. Results indicated that buckwheat kilned at 40°C had an apparent fermentability of
61.8%. This was low in comparison to the apparent fermentability of the control barley malt fermentation
(82.7%). The low levels of fermentable sugars correlated
well with low amylolytic activity generated during germination of buckwheat 39,40. Buckwheat malt was found to
have low levels of ␣- and ␤-amylase, when compared to
barley malt (see Table I). The quality of malt and wort is
considerably compromised when malt contains low amylolytic levels. With optimised kilning and mashing procedures, fermentability may be more comparable to that of
barley.
Nitrogenous compounds (TSN and FAN)
Nitrogenous compounds can affect foam, mouthfeel
and the tendency to form haze in the final beer 7. Results
indicate that buckwheat malt contains a lower level of
TSN than worts obtained from barley malt. FAN levels in
buckwheat malt were similar to FAN levels in barley malt
(107 mg L–1) suggesting that FAN levels most likely are
sufficient to guarantee a healthy fermentation, once kilning and mashing programs are optimised.
CONCLUSION
This study elucidates the impact of kilning on moisture
content and enzymatic activity, specifically ␣-amylase, ␤amylase (total and soluble), ␤-glucanase and protease activity during the malting of buckwheat. Based on the results of this study, it can be concluded that prolonged
kilning at 40°C causes greater inactivation of endo-␤-glucanase and ␣-amylase activity in comparison to ␤-amylase and protease activities. However the latter is still affected by the kilning regime. This highlights the need to
study the effect of a two-stage kilning regime for shorter
time periods. In general, it was found that malt and wort
made from buckwheat kilned at 40°C for 48 h with optimized steeping and germination conditions, shows potential as a gluten-free brewing ingredient once kilning and
mashing procedures are optimized to ensure survival of
the enzymes.
ACKNOWLEDGEMENTS
The Authors would like to thank Trouw B.V. (Rotterdam, The
Netherlands) for supplying the buckwheat samples and Vikas
Kaushik for the freeze-drying of the grain samples. We would
also like to thank Dave Waldron for his help.
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(Manuscript accepted for publication November 2005)
ERRATUM
A correction was made in this paper on November 30, 2005. In the
last paragraph on page 294, the first sentence referred incorrectly to
Fig. 5. The text was changed to refer to Fig. 4 (“Fig. 4 depicts the
relative enzymatic activity of ␣-amylase during the kilning stage of
malting buckwheat”).
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