Cereal Chem 67:421-427   |  VIEW ARTICLE

Relation of Wheat Hardness to Air-Classification Yields and Flour Particle Size Distribution.

Y. V. Wu, A. C. Stringfellow, and J. A. Bietz. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

Hardness of 14 wheats was related to particle size distribution determined by Buhler milling. Hard and soft wheats differed in percentage of flour that passed through a 270-mesh screen (53-micrometer opening) but was retained on a 325-mesh screen (44-micrometer opening), in percentage of flour that passed through a 325-mesh screen, and in mean flour particle size after 10 min of screening. Effects on particle size of varying the amount of flour screened and length of time on a Ro-Tap sieve shaker were studied. Hard and soft wheats also were distincly different in percentage of coarse residue (greater than 30 micrometers) from air classification of flour and from flour pin-milled at 9,000 rpm or at 9,000 followed by 14,000 rpm. Hard red spring wheats appeared to differ from hard red winter wheats in percent less 15-micrometer fraction from air classification of flour further pin-milled at 9,000 rpm and three times at 14,000 rpm, and also in percentage of 24-30-micrometer fraction. Thus, greater than 30-micrometer fraction from air classification or screening of flour distinguishes hard and soft wheats, whereas the less than 15-micrometer fraction from air classification also differentiated hard red spring from hard red winter wheats.