MALTING QUALITY TRAITS - Canadian Malting Barley Technical ...

production, consequently uneven chitting, and uneven growth. If the aeration during
the wet periods, or the CO 2 removal during the air-rest periods are not adequate, or the
steep water temperature and/or the grain temperature are too high, uneven growth and
subsequent non-uniform modification can also result. The uniform kernel size, delicate
husks and easily hydrated endosperm structure of Canadian varieties dictate that care
must be taken not to oversteep the barley.
At a steeping temperature of 12-18°C, it is expected that the first wet period /immersion
of 6 to10 hours will result in a barley moisture of 30 to 35%. The first air-rest
should be long enough (8 to12 hours) to enable the barley to commence chitting prior
to the second immersion (6 to 10 hours). The second air-rest (6 to 8 hours) and the
third immersion (2 to 4 hours) are designed to elevate the final moisture content of the
steeped barley to approximately 43 to 45% and a chitting rate above 80%. During immersion,
adequate aeration is required to aid the washing and mixing of barley grains
in the tank, as well as to replace the depleted oxygen in the steep liquor. During air rest,
CO 2 suction is necessary to remove CO 2 and to control grains’ temperature. However
over-suction of CO 2 during air-rest also needs to be avoided, because it may cause the
surface layer of the barley grain to dry up and cause undesirable uneven temperature
distribution in the grain and consequently uneven water hydration. If a two-immersion
cycle is employed, the final moisture content is adjusted by spraying water during the
germination stage.
An alternative to multiple immersion steeping is spray steeping, in which the initial
immersion is followed by spraying water onto the surface of the grain (alternated with
aeration periods) until the desired moisture content is achieved. As a result of difficulties
in controlling hydration and chitting rate, the spray steeping cycle is not commonly
used for processing Canadian barley varieties.
During germination, the steeped barley needs to germinate for a period of 3.5 to 4
days at temperatures ranging from14 to 20°C, to complete the modification process. The
required germination time may vary, depending on the barley varieties being malted,
the germination temperature, and the target malt analysis. In some cases, a temperature
regime is maintained such that the temperature decreases during germination (start at
20 reducing to 14 °C), although in most cases, the temperature during germination will
remain constant. Warm conditions at the start of germination promote early development
of soluble protein, while germination at lower temperatures favours complete
breakdown of cell walls (Beta-glucans) in the endosperm while avoiding excessive protein
solublization (when the time of germination is extended). Usually there is no need to
add gibberellic acid or other additives to the green malt. Germination conditions are
achieved by passing humidified air through the grain bed at a rate of 10 – 13 cubic m 3 /
min/tonne. A mechanical turner passes through the grain bed at regular intervals (usually
8 to 12 hours) to prevent “matting” of the rootlets and compaction of the grain bed.
Water sprays may be applied during turning to replenish moisture loss, but the quantity
of spray water should be kept to a minimum. If adequate steep-out moisture is obtained
at steeping, it is possible to avoid water spray during germination. Spraying water during
germination tends to cause increased malting loss and enhance soluble protein development.
Spraying late in germination can fully re-hydrate the embryo without appreciably
wetting the endosperm and cause excessive vegetative growth without further accelerating
modification. Like processing any barley, higher temperatures and green malt moisture
content promote more enzyme development and rapid modification, but also leads to
more vegetative growth (rootlet and acrospire) and higher respiration losses.
The kilning process can be generally completed within a 24 hours period. Weather
conditions and equipment design may require longer periods. Modern single deck
kilns are generally more efficient at achieving the desired drying conditions than traditional
double-deck systems. Indirect fire system is preferred to avoid formation of
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