342 Improving Hagberg Falling Number values through density and size separations.

P. J. BUNN (1), G. M. Campbell (1), S. C. W. Hook (2), and C. Webb (1). (1) Satake Centre for Grain Process Engineering, P.O. Box 88, Manchester, UK; (2) RHM Technology Ltd., Lord Rank Centre, Lincoln Road, High Wycombe, Buckinghamshire, UK.

The relationship of Hagberg Falling Number (HFN) and density separations made using a Specific Gravity Separator has been well documented from the mid 1980s. Here, the influence of grain size in the operation of gravity separators is examined through fluid mechanics. In fluidised systems with Reynolds Numbers <1.00 surface friction is the primary cause of drag; therefore, grain size and texture will influence the operation of gravity separators. To assess the relative influence of these parameters UK wheat samples were separated by thickness and density prior to assessment of HFN. Low density samples showed lowest HFN values. Grains of thickness <2.50 mm showed HFN values significantly lower than the other size fractions. Grain size and density have been found to be independent of each other. This suggests that gravity separators are separating by both criteria, rather than density alone. The proportion of material less than 2.50 mm thickness corresponds with the proportions of low grade material produced by workers using gravity separators to improve wheat quality. Most grain handling plants contain sieving equipment for dockage removal; if it is possible to separate low Hagberg grains by this method the pressure on gravity separators would be reduced.