Barley for Food and Health: Science, Technology, and Products

WHOLE-GRAIN PROCESSING 115
kernel is thus modified over a period of four to five days and sometimes up to 10
days in traditional floor malting, which is performed at 13 to 16 ◦ C. In modern
pneumatic malting houses, temperature is controlled typically over the range 16
to 20 ◦ C. Increasing the temperature to 25 ◦ C produces roots and enzymes more
quickly; however, the rate of enzyme formation decreases such that grains germinating
at lower temperatures ultimately contain higher enzymatic activity. Long,
cool germination cycles maximize fermentability and also minimize malting loss
(Bathgate et al. 1978). Native amylolytic and proteolytic enzymes in the kernel
are activated by the moisture and temperature and enhanced by gibberellin,
converting insoluble starch into soluble sugars and oligosaccharides. Proteins are
converted to free amino acids and peptides by proteolysis. When this modification
has reached the maltster’s desired stage, the greenmalt, asthematerial
is now known, is transferred to the kiln for drying, the third and final stage of
processing.
Germination is arrested in the kiln, where warm air passes through the malted
grain. The drying process causes withering and stabilization of the grain structure.
Kiln drying is divided into four merging phases: free drying down to about
23% moisture, an intermediate drying stage to about 12% moisture, decreasing
moisture from 12% to about 6%, and curing where moisture is taken down to
2 to 3%. During free drying, an air temperature of 50 to 60 ◦ C is attained along
with an airflow of 5000 to 6000 m 3 /min, causing unrestricted removal of water.
When moisture content reaches about 12%, the water in the malted kernel is
said to be bound, requiring further increase in air temperatures and reduction of
air fan speed. Lowering of moisture to about 6% allows the malt to be “cured”
with the air temperature increased to 80 to 110 ◦ C, reducing moisture to 2 to
3%. Drying time and temperatures are essential in developing the flavor and
color characteristics of the finished malt, this being a critical point in the malting
process. Making specialty malts, as for use in food, differs from the basic malting
process for beverage production in that batch sizes are smaller and constant
monitoring is required to meet specifications (Kent and Evers 1994; Gibson 2001;
Briess Industries). Malted kernels can be used directly in breads or other bakery
products or processed further into flour extracts or syrup. A characteristic of malt
products is the presence or absence of enzymes. Malt ingredients that contain
diastatic enzymes are used in brewing. Nondiastatic malt products are processed
at varying higher temperatures, which destroys some or all of the enzymatic
activity. Diastatic malt flour is commonly used in bread baking in small amounts
to act as a dough conditioner (Hansen and Wasdovitch 2005).
Malt employed in the distilling industry to produce whiskey is made from
maize, rye, and barley grains. Specifications placed on malt for distilling are
comparable to those employed for brewing malt. Residual levels of unfermented
dextrins are irrelevant to the flavor of whiskey, although they are desirable in beer
and food malts. The goal is the maximum production of ethanol. Malt vinegars
are produced by the bacterial oxidation of alcohol from wine, cider, or beer to
acetic acid. Production of malt vinegars requires high fermentability of the grist
so as to maximize ethanol production, as in distilling. Accordingly, high-diastatic