Cereal Chem 69:632-636   |  VIEW ARTICLE

Effect of Degree of Milling of Brown Rice and Particle Size of Milled Rice on Starch Gelatinization.

W. E. Marshall. Copyright 1992 by the American Association of Cereal Chemists, Inc. 

Unmilled and milled Lemont long-grain rice samples were evaluated by differential scanning calorimetry to determine the effect of abrasive milling or disruption of kernel integrity on starch gelatinization. Kernel integrity was disrupted by pulverizing kernels to different particle sizes, and starch gelatinization was measured for the various fractions. Unmilled (brown) rice kernels had higher gelatinization onset (To), peak (Tp), and conclusion (Tc) temperatures than any milled sample. Partial removal of the bran layer resulted in a sharp decrease in these temperatures. Continued abrasive milling further decreased Tp and Tc until the degree of milling reached about 20%. Further milling to 66% had little effect on the gelatinization temperatures. Gelatinization enthalpies (DeltaH) increased until a 20-25% degree of milling was attained, but no additional change was observed upon further milling. In contrast, reduction in particle size caused a large decrease in Tp, Tc, and DeltaH but only a modest decrease in To. These results indicate that starch gelatinization can be altered through abrasive milling or changes in particle size.