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R. Gracza. Copyright 1960 by the American Association of Cereal Chemists, Inc. A conventionally milled hard red spring wheat flour was fractionated by repeated air classifications. The repetitive procedure, starting with separation at low particle size, produced fractions with protein contents as high as 20.3% and as low as 8.8% from a parent flour of 13.8% protein content and 86% extraction (flour basis) of a 100% Montana hard spring wheat. The degree of protein shifting index shows that 5.4% of the parent flour's 13.8% protein could be shifted within the fractions, compared to 27.7% protein shifting in the identically processed 7.8% protein content soft red winter wheat flour described in a previous paper. Other indices such as ash, diastatic activity, alkaline water retention capacity, thiamine, fat, and MacMichael viscosity appreciably increased with increasing protein content and/or specific surface within the subsieve size range. Bulk density increased with increasing particle size, whereas specific gravity decreased with increasing protein content in the fractions. The pH value reached its maximum in the fraction of lowest protein content. Physical dough test data indicate that the dough development time increased with increasing protein content. Absorption, however, increased not only with the protein content but also with decreasing particle size, i.e., increasing specific surface. Doughs made from flour particles collected in the 44.5 to 48.0 SED micron size range yielded extensigrams characteristic of good bread flours, whereas doughs made from flour particles collected in the 23.0 to 39.0 SED micron size range produced farinograms and extensigrams characteristic of soft wheat flours used in pastries. |
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