Predicting wheat quality is an important goal of the grain industry. Laser diffraction sizing (LDS) was used to measure particle size distributions of wheat flour and isolated starch to determine if the method could be used as a component for predicting end-use quality. Five hard red winter and five soft red winter wheats were milled into flour from which starch was isolated. Flour particle size distributions were measured using a dry module as well as flour suspended in isopropanol (AACC Approved Method 55-40). Analysis using isopropanol as a suspension fluid caused smaller particles (<8 in diameter) to be released from flour. Use of isopropanol caused a shift to larger particle sizes between 8 and 400 in comparison to dry analysis. Isopropanol also caused clumping with spurious particles found between 250400. LDS of isolated starch showed a separation of A- and B-type granules between 9.8 and 10.8 for the soft wheats and between 8.2 and 9.8 for hard wheats. Hard wheats had a larger volume of starch in the A-type fraction while the soft wheats had more starch in B- and C-type fractions. A demarcation between the B- and C-type starch was only observed for the soft wheats and that was when data was presented as percent surface area. LDS may prove to be a valuable tool in helping predict wheat end-use quality since flour and starch differences were observed between wheat classes as well as among wheats within a class.
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