Fargo, North Dakota
September 4, 2008
The reports on yield and quality
of the 2008 barley crop that are coming into the
North Dakota State
University Institute of Barley and Malt Sciences (IBMS) are
good.
However, lower than optimal grain plumpness and higher than
desired protein levels have been reported in areas of Idaho,
Montana and North Dakota.
Deoxynivalenol (DON), mold and preharvest sprouting have been
observed in some later crops in North Dakota.
Low plumpness and high protein mostly are attributable to high
temperatures and moisture stress during grain filling.
These factors are of concern to maltsters and brewers for a
number of reasons, according to Paul Schwarz, IBMS director.
"The main concern with these factors is that they predict
potentially lower extract in the finished malt," Schwarz says.
"Extract determines the amount of malt that must be used by the
brewer to produce a given volume of beer, so it is an economic
concern. Typically, 79 percent to 81 percent of the grain is
extractable in laboratory tests."
Most of the extract and all fermentable sugars are derived from
starch. Starch synthesis occurs during grain fill, but when
environmental stresses reduce this process, less starch and
proportionally more protein are formed in the kernel.
The grain then tends to be thinner and has a higher proportion
of husk to endosperm.
"Aside from the extract, there are a number of other problems
associated with the malting and brewing of high-protein barley,"
Schwarz says. "High protein can lead to haze problems in the
beer and it is more difficult for maltsters to control the color
of the malt during processing. Beer color is derived from the
malt. Most popular American beers are very light in color.
Higher protein barley tends to yield dark malts."
Protein content and kernel plumpness affect the speed at which
barley goes through the malting process. In malting, the grain
first is soaked in water
("steeping") to approximately 45 percent moisture. It then is
allowed to germinate for four to five days until the proper
modification or changes in the grain structure and composition
are achieved. The germinated barley then is dried, ("kilning")
to approximately 5 percent moisture. The entire process takes
six to eight days, depending upon the sample.
Thin grain will absorb water and modify at a faster rate than
plump grain. In samples with a wide distribution in kernel
plumpness, maltsters first may grade the barley into a number of
size fractions and malt them separately. Grading is required
more frequently with six-rowed barley than with two-rowed, but
can be used to achieve better uniformity in the final malt.
Protein also affects the rate of water uptake and speed of
modification. For this reason, maltsters will segregate
shipments by protein content and malt them separately.
One other issue that tends to arise when discussing protein in
malting barley is whether to blend high- and low-protein barley
lots to meet protein specifications. The result of this would be
a nonuniform rate of modification during malting. This leads to
serious problems for brewers.
Essentially, some of the grain in such a sample may be modified
properly, while another portion is over or undermodified.
Dealing with nonuniform malt actually is a larger problem than
dealing with a uniform high-protein sample.
The result concerning protein in malting barley is that
maltsters and brewers generally are reluctant to use six-rowed
barley with more than 13.5 percent protein and two-rowed with
more than 13 percent.
"However, these limits vary between specific companies and
depend upon their brewing processes and the products produced,"
Schwarz says. "Some protein is needed in brewing for things such
as for good beer foam and proper yeast growth during
fermentation. Therefore, there also are minimal limits on
protein, but low protein is rarely a problem, especially under
dryland barley production." |
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