Slides
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Barley and Malt
Karl J. Siebert
Introduction
Of the four main ingredients of beer (malt, hops, yeast and water), malt
is considered by many to be the most important. It has often been called
the "soul of beer". Malt means malted barley, although it is possible to
malt other grains, most notably wheat and rye. After harvest and storage to
overcome dormancy, the barley is malted.
Barley
Barley is a grain that very much resembles wheat. It can grow from the
Arctic Circle to the Equator. Barley cultivars are classified according
to the arrangement of kernels (the seeds) around the grain head as
either two-row or six-row. More important to the maltster and brewer is
the division into malting barley and feed barley. Only some cultivars
(including some two- and some six-row barleys) are considered suitable
for malting. Immediately after harvest, barley is dormant, or incapable
of sprouting (germination). It needs to be stored for a time (usually a
few months) before it can be malted. The malting process has three
stages: steeping, germination and kilning.
Steeping
In steeping, which typically takes
1 to 2 days, the grain is placed in a tank which is then filled with
water. Air is vigorously bubbled through from the bottom. At various times the
water is drained out and replaced. This serves to remove surface dirt, raise the moisture
content of the grain and to provide oxygen for respiration.
Germination
The steeped barley is then transferred
to a flat bed where germination occurs, typically over 4-5 days. The bed
has slots in the bottom through which air is passed to allow the grain
to respire. Water sprays are used to maintain high moisture and the
grain is turned from time to time. The barley seed begins to grow and
puts out a sprout and rootlets. In order to do this, the seed must first
produce the enzymes needed to utilize its carbohydrate reserve (in the
form of starch). In order to build these enzymes the grain must first
break down storage proteins to produce the simple amino acid building
blocks.
Kilning
Kilning is carried out by passing
copious quantities of air through the "green" malt while a temperature
program (with holds and rises) is carried out. This is designed to
minimize damage to the carbohydrate and protein degrading enzymes, while
removing moisture to stabilize the malt. During the higher temperature
stages the heating results in the development of malt color and flavor.
Different types of malts are produced with different temperature
programs.
Changes During the Malting Process
The moisture
contents of barley and malt are similar. However, barley is very hard,
while malt is much softer; that occurs because digestion of some of the
protein and starch produces changes in the internal grain structure.
Malt contains much higher levels of enzymes than barley. Malt color can
be similar to that of barley (pale malts) or very much darker.
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FS430:
Understanding Wine and Beer