Parboiling, a hydrothermal treatment of paddy or brown rice, impacts both head rice yield and texture
and nutritional characteristics of cooked rice. Here, milling breakage susceptibility of parboiled brown
rice was investigated on both bulk and kernel level. Brown rice was parboiled by soaking at 40, 55 or
65 C and steaming at 106, 120 or 130 C. The breakage susceptibility and changes in starch and proteins
of bulk samples were related to the properties of individual rice kernels. An increase in milling breakage
susceptibility from 1% to 11% corresponded to a decrease in average bending force of individual kernels
from 34.9 to 14.6 N. Furthermore, both white bellies and fissured parboiled rice grains were more
breakage susceptible. Their average bending force was respectively 14.1 N and 17.6 N compared to an
average of 39.6 N for intact parboiled rice grains. Whereas the level of proteins extractable with sodium
dodecyl sulfate containing medium had no impact, the degree of starch gelatinization was critical in
determining the presence of both white bellies and fissured parboiled rice grains. More in particular,
complete starch gelatinization ensured the absence of white bellies and minimized fissuring in the
parboiled end-product, thereby decreasing milling breakage susceptibility.
Parboiling, a hydrothermal treatment of paddy or brown rice, impacts both head rice yield and texture
and nutritional characteristics of cooked rice. Here, milling breakage susceptibility of parboiled brown
rice was investigated on both bulk and kernel level. Brown rice was parboiled by soaking at 40, 55 or
65 C and steaming at 106, 120 or 130 C. The breakage susceptibility and changes in starch and proteins
of bulk samples were related to the properties of individual rice kernels. An increase in milling breakage
susceptibility from 1% to 11% corresponded to a decrease in average bending force of individual kernels
from 34.9 to 14.6 N. Furthermore, both white bellies and fissured parboiled rice grains were more
breakage susceptible. Their average bending force was respectively 14.1 N and 17.6 N compared to an
average of 39.6 N for intact parboiled rice grains. Whereas the level of proteins extractable with sodium
dodecyl sulfate containing medium had no impact, the degree of starch gelatinization was critical in
determining the presence of both white bellies and fissured parboiled rice grains. More in particular,
complete starch gelatinization ensured the absence of white bellies and minimized fissuring in the
parboiled end-product, thereby decreasing milling breakage susceptibility.
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