2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Breakage of a mixture of kernels during First Break milling of wheat depends on the distributions of single kernel parameters such as size, hardness, moisture content and density. Using an experimental test roller mill, breakage equations have been developed relating input and output particle size distributions over a roller milling operation. Predictive equations describing breakage of hard and soft wheat varieties have been developed, in terms of kernel size distribution, moisture content, roll gap and roll disposition (sharp-to-sharp, dull-to-dull etc.). Increasing the roll gap or decreasing the average kernel size increases the proportion of large particles in the milled stocks. Increasing moisture content produces more large and small particles, with fewer in the mid-range, giving a more "U-shaped" particle size distribution. Sharp-to-sharp milling gives a broad, even particle size distribution over the range 250-2000 microns, while the transition through sharp-to-dull, dull-to-sharp through to dull-to-dull gives progressively more "U-shaped" distributions with greater distinction between large and small particles. Milling of PeriTec debranned wheat gives narrower particle size distributions with less material in the larger size range. The breakage equations allow the effects of altering milling conditions to be predicted quantitatively, allow prediction of the milling of a mixture of wheat varieties, and form a basis for linking SKCS parameters to milling performance.