PARTICLE-SIZE CHARACTERIZATION OF GROUND FRACTIONS OF DENT AND FLINT MAIZE

Twenty-six samples of hybrid maizes (ROSSO flint maize, VOLGA dent mai ze, DEA and MONARQUE flint-dent maizes) were dry-milled and separated into fractions. The milling yield was determined. Particle size was me asured by mechanical sieving for grits, and by laser diffraction for c oarse and fine semolina and flours. Bimodal particle size distribution s of fine semolina and flours were analyzed as a function of mode size and proportion. The proportions of the particle size classes in each fraction of the 26 samples were studied by Factorial Correspondence An alysis (FCA). Despite inherent variations in culture conditions, diffe rences were apparent between VOLGA and the other three hybrids. The pr incipal mode was characteristic of the fraction considered, without cl ear varietal differentiation. Analysis of the secondary mode of fine s emolina and flours showed that it was principally due to particles sim ilar in size to starch granules (14 to 17 mu m), VOLGA particles being smaller than the others. The relative ''weight'' of the secondary mod e was greater with VOLGA than with the other maize types. The four FCA s showed that VOLGA was clearly differentiated from the other hybrids, the difference being greater for the fine semolina and flour than for grits and coarse semolina. The small differences observed between DEA and the ROSSO and MONARQUE hybrids were not significant. A technologi cal behaviour index is proposed: the calculated quantity (g) of very f ine particles constituting the secondary modes of fine semolina and fl ours (per 1 g of ground maize). This index is inversely correlated wit h the yield of grits (r(2) = 0.913 for the 26 samples), and may theref ore prove useful in the cultivation and processing of maize.