MALTING QUALITY TRAITS - Canadian Malting Barley Technical ...

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Chapter Four
(2) The Curing Stage
The curing stage begins after the “drying front” (moisture removal from the green
malt bed takes place in layers, the lower layers dry first, the basal drying zone progressively
moving upward), reaches the surface of the grain bed, which is accompanied by
the so-called ‘breakthrough’ (a point of time when the drying zone reaches the upper
surface of the grain bed). Therefore this stage is sometimes referred to as the “post-break”.
During this part of the cycle, the moisture content of the malt is further reduced to its
final level of approximately 4% from the 10-12 % achieved in the free drying stage. In
contrast to the drying stage, this stage is a much slower drying process since the rate of
water removed from the barley is much slower, requiring more time. During this stage,
the air-on temperature may be increased to 65-75°C with a progressive air volume reduction
and increment of air recirculation. In the final part of the curing stage, the air-on
temperature may be increased to 80-85°C for 3-4 hrs for production of pale malt, and
up to 100°C for production of ale malt. The complex chemical reactions between the
products of starch degradation and protein degradation (i.e. sugars and amino acids) at
high temperature produce the typical colors, flavors and aromas associated with malts.
Enzyme actions are largely halted and some enzymes have been destroyed, although the
final malt still contains adequate levels of enzymes for successful brewhouse performance.
After kilning, the malt must be cooled to room temperature (preferably to 20°C or
less) to avoid further color formation and enzyme destruction. Usually this is accomplished
by cooling the malt below 37°C, and then cleaning it to remove rootlets, sprouts
and loose husks. The finished cleaned malt is then transferred to storage silos that are
arranged according to variety and quality specifications. After a target aging period,
malt with similar quality from the silos are blended to meet the precise specifications
required by the brewers, then go through a final cleaning prior to loading into a truck
or railcar for shipping.
In theory, from the same batch of “green malt” unlimited types of malt could be
produced by kilning the green malts under different conditions. This further emphasizes
the importance of the kilning stage for quality malt production.
Processing Canadian malting barley varieties
The key malting stages of malt have already been outlined in this section. The discussion
here will focus on how to malt Canadian barley and to fully utilize its quality
potential. The scope of these discussions will be limited to producing pale malt, because
the greatest amount of malt produced in North America and in other parts of the world
is pale malt.