Cereal Chem 65:486-492   |  VIEW ARTICLE

Particle-Size Related Physical Properties of Flour Produced by Smooth Roll Reduction of Hard Red Spring Wheat Farina.

M. G. Scanlon, J. E. Dexter, and C. G. Biliaderis. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

Hard red spring wheat farina was reduced at all possible combinations of three roll gaps and three differentials using a roll stand of the 254-mm Grain Research Laboratory experimental mill equipped with smooth frosted rolls. The flour produced was separated into three particle-size fractions by sieving through 91- and 53-micrometer aperture sieves. The less 53-micrometer fraction exhibited much greater starch damage than the coarser fractions. Increasing differential and decreasing roll gap increased starch damage for chop and the two coarser fractions. Greater compressive stresses (from reduced roll gap) did not affect the starch damage of the less 53-micrometer fraction, possibly because greater stress caused more fracturing rather than altering the mode of particle release from the parent farina. The fracture mode is thought to start at the starch granule-protein interface. Increased differential increased the starch damage in the less 53- micrometer fraction. Shear forces applied by the differential at the starch-protein interface would alter the mode of fracture. The ratio of starch damage estimated by amylose extractability to starch damage estimated by alpha-amylase digestibility increased with increasing differential for all three particle-size fractions, substantiating the hypothesis that differential would initiate crystallite slippage in the amorphous regions of the granule. Higher flour ash and darker flour color values at 1:1 differential were explained as a consequence of brittle fracture occurring through the more proteinaceous regions, since at 1:1 differential crystallite movement is inhibited due to reduced shearing forces.