Breakage of rice during milling - effect of kernel defects and grain dimension.

Ten lots of paddy having varying dimensions and contents of cracked
and immature grains were milled using laboratory McGill equipment.
Grain breakage seemed to originate almost entirely from kernel defects,
for it rarely exceeded the content of defective grains. In short and round
varieties, a good part of the highly defective (HD = multiple-cracked and
immature) grains but few of those with a single transverse crack (STC)
broke during shelling, and the remaining HD grains seemed to break during
pearling. In medium and slender varieties, most HD and a good part
of STC grains broke during shelling, any remaining HD (but not STC)
grains appeared to break during pearling. Breakage during pearling increased
(within the above limits) with increasing degree and pressure of
milling. Improved shelling gave substantial advantage for undermilled
rice, but only a moderate advantage for highly milled rice.