Program Book - Master Brewers Association of the Americas

O-20
Changes in protein and amino acid composition during
malting—A comparison of barley and oats
CHRISTINA KLOSE (1), Beatus Schehl (1), Elke Arendt (1)
(1) Department of Food and Nutritional Sciences, University
College Cork, Cork City, Ireland
Barley (Hordeum vulgare) has been traditionally used for the
production of malt, whereas malted oat (Avena sativa) was widely
used in medieval times and before. Nowadays oat malt is used in the
brewing industry as a flavor adjunct for the production of special
beers. The most important aim during malting is to generate starch
degrading enzymes. However, the protein content of malt is of
central importance with regard to filtering, fermentability, foam
and haze stability. The purpose of this study was to evaluate the
changes in protein and amino acid composition from the raw barley
and oat over germination to the final malt using a range of methods.
After extracting the cereal proteins on the basis of their solubility
(Osborne fractionation) the different protein fractions were analyzed
using a Lab-on-a-Chip technique, which separates the proteins,
based on their molecular weight, by capillary electrophoresis. This
new technique for the analysis of proteins was supported using
two-dimensional gel electrophoresis. In addition, amino acid
analysis was carried out, using a chromatographic method. The
proteolytic activities of the grains were measured at various stages
during malting. It was found that the overall proteolytic activity
increased during germination. The values reached for barley after
malting (21.39 mg g –1 h –1 ) were slightly higher than those of oats
(20.31 mg g –1 h –1 ).Results of the Lab-on-a-Chip analysis revealed
that protein degradation during malting was higher in barley than
in oats. Especially the storage protein fraction of barley (hordeins),
as well as the glutelin fraction, was degraded completely, whereas
the oats prolamin and glutelin fraction were not entirely degraded.
In the main protein fraction of oats (globulins) many proteins could
be detected, where only a few were found in the barley globulin
fraction. In both albumin fractions, which contain the metabolically
active proteins, increases of proteins could be observed. The results
obtained from the two-dimensional gel electrophoresis followed the
same trend as the Lab-on-a-Chip results. A deeper understanding
of the protein changes was achieved by amino acid analysis of the
unmalted and malted grains. Due to the higher protein content of
oats, detectable amino acid levels were higher in oats than barley.
Glutamic acid was found to be the amino acid with by far the highest
concentration of all amino acids in both barley and oat grains.
Amino acid composition of the grains was comparable.
Christina Klose received a M.S. degree in food technology from the
Technische Universiät München-Weihenstephan in 2006. During her
studies, she did three work placements in two dairy companies and
a brewery. During her master thesis, “Investigations on the Stability
of Folic Acid, Pantothenic Acid and Riboflavin in Non-alcoholic
Beverages,” she worked at Doehler, Darmstadt, Germany. Since
October 2006, Christina has been working on her Ph.D. thesis in the
Department of Food and Nutritional Sciences at University College
Cork, Ireland, where she is investigating protein changes in barley
and oats during malting and brewing. Christina is member of the
ASBC.
74
O-21
Heat treatment of barley restricts Fusarium activity during
malting
ARJA LAITILA (1), Tuija Sarlin (1), Riikka Juvonen (1), Petri
Peltola (2), Pekka Reinikainen (2), Erja Kotaviita (3), Silja Home
(1), Annika Wilhelmson (1)
(1) VTT Technical Research Centre of Finland, VTT, Finland; (2) LP
Research Centre Ltd., Lahti, Finland; (3) Raisio plc, Raisio, Finland
Several filamentous fungi, including fusaria, are sensitive to
heat. In this study barley was heat-treated prior to the malting
process in order to inactivate the Fusarium fungi during malting.
Two-row Scarlett and six-row Tradition barley samples were
exposed to heat (60–100°C) for 5–10 seconds prior to steeping.
In addition to traditional culturing techniques, the changes in
the Fusarium communities during malting were followed with
PCR-DGGE (Polymerase Chain Reaction–Denaturing Gradient
Gel Electrophoresis) and real-time PCR. Barley samples taken
during processing were also analyzed for trichothecenes and
for hydrophobins, also known as gushing factors. Furthermore,
this study investigated the effects of heat-treatment on grain
germination, gushing potential, enzyme activities and mashing
performance. This study clearly showed that Fusarium growth could
be effectively restricted by exposing the grains to steam prior to the
steeping phase without influencing grain germination. Moreover,
heat-treatment significantly reduced production of harmful
Fusarium metabolites during malting. It inhibited mycotoxin
formation and alleviated the gushing tendency. We also observed
that restriction of fungal activities led to less extensive proteolysis
and lower activities of xylanase and heat-stabile β-glucanase, as well
as slightly lower wort separation. In order to balance the microbial
communities in malting and to improve the process efficiency,
heat-treatment could be combined with multifunctional microbial
mixtures. Selective control of microbial populations with mild
treatments in various steps along the barley-malt-beer chain could
result in a successful strategy to suppress harmful organisms and to
simultaneously enhance beneficial microbes contributing to malt
modification and malt brewhouse performance.
Dr. Arja Laitila studied food microbiology at the University of
Helsinki. She holds a Ph.D. degree in food sciences. She joined VTT
Technical Research Centre of Finland in 1993. Arja has participated
in several national and international projects related to microbes in
cereal-based bioprocesses. Since January 2008, she has been a team
leader of microbes and cereal processing at VTT. Her particular
expertise is malting and brewing microbiology.