World Grain - September 2019 - 53

would not be representative of the crop. Representative
sampling is essential if the results of the laboratory milling
are to have any value.
Samples of grain must be prepared with care in order
to produce meaningful results and protect the laboratory
milling equipment. Dockage should be removed, especially
any sticks and stones that might otherwise damage equipment. All samples to be compared must be treated identically as they would most likely be in the commercial mill.
It is not appropriate or meaningful to screen out shrunken
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remaining samples in the set.
As with cleaning, the conditioning of samples to be
milled must be painstakingly controlled and uniform if labRUDWRU\PLOOLQJUHVXOWVDUHWRLGHQWLI\GL൵HUHQFHVLQZKHDW
performance. Samples must be tempered to the same moisture and held for the same amount of time at the same temperature prior to laboratory milling. The required amount
of water is added to the grain in a manner to ensure its
uniform distribution across all kernels. Tempering moisture level and time may vary by wheat class and desired
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Like sampling, cleaning and conditioning, the laboratory

mill operation must also be attentively monitored and controlled. The laboratory milling environment must be maintained at a constant temperature and relative humidity (2124°C, 60-65% R.H.) to control moisture loss and changes
in milling and sifting characteristics. The temperature of
the milling surfaces should also be maintained at a constant
temperature. Roll chills warm when being used due to the
dissipation of energy applied to the wheat during the grinding process. As a result of heating, roll gap decreases due to
thermal expansion of the roll chill. Changes in roll gap inÀXHQFHPLOOLQJSURSHUWLHVVXFKDV\LHOGDQGEUDQFOHDQXS
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damage and absorption.
Some researchers recommend maintaining laboratory
mill temperature overnight when the mill is not in operation by using a resistance heater or heat lamp. Some of
the same people recommend running both a warm-up and
control sample to heat equipment surfaces and check mill
settings at the start of a test run. Mill temperature is so
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to allow mills to cool/equilibrate during long days of operation when many samples are being processed.
Other factors to be controlled when evaluating a set of
samples includes feed rate, roll selection, roll gap setting,

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World Grain - September 2019

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