-

In order to obtain some quality properties of wheat and rice kernels, which may be
utilized for end–use property assessment, stress relaxation and uniaxial compression
tests were conducted on wheat and rice kernels. In these tests, the effects of moisture
content, strain level, and type of loading probe were investigated on mechanical
properties of the two cereal grains. Along with measurement of mechanical parameters,
stress relaxation tests were also carried out on wheat grains. Using these tests, the
coefficients of two fitted polynomial equations were extracted from the curves as the
indices of shape of curve. Based on the results, a linear relationship was defined relating
the ratio of force decay, as a factor of stress relaxation curve, the force factor and c1
and d2 coefficients (of polynomial eq.’s), to the wheat hardness (an index of wheat
milling quality). It was found that, wheat moisture content had a critical effect on the
results. The effect of strain level on the results shows the considerable variations in
mechanical properties, due to increase in strain level. According to the results of
uniaxial compression tests and the strength properties of rice grain (extracted from the
force – deformation curve), it was found that different varieties of rice can be classified
based on measured parameters. In addition, use of two types of loading probes showed
that for each kind of probe, a specific characteristic of grain tissue can be assessed.