Cereal Chem 65:171-174   |  VIEW ARTICLE

Factors Affecting the Abrasive Dehulling Efficiency of High-Tannin Sorghum.

M. A. Mwasaru, R. D. Reichert, and S. Z. Mukuru. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

High-tannin sorghum gives low yields when the grain is abrasively dehulled. Consequently, the factors affecting dehulling performance of this grain were investigated with a small-sample dehuller, the Tangential Abrasive Dehulling Device. Ten grinding wheels, which varied in grit size, grade, structure, and surface finish, were specially manufactured and tested on three soft-endosperm, high-tannin sorghum cultivars. Flour extraction (tannin), defined as 100 minus the required percent kernel removed to reduce the tannin content to 0.5%, ranged from 19 to 91%. All cultivars could be dehulled at low throughputs with flour extraction (tannin) greater than 70% by using a grinding wheel with a low disk abrasive index; a low index was achieved by decreasing the grit size, by increasing the grade or the structure, or by using grinding wheels with a smooth surface finish. The independent effects of grain tannin content, hardness, and shape on dehulling performance were investigated by testing lines that varied widely in one variable but were similar in the other two. Flour extraction (tannin) was significantly correlated with tannin content (r = -0.98, P less than 0.01), hardness (r = 0.84, P less than 0.01), and seed shape (r =0.74, P less than 0.05). Development of harder, rounder grain with the minimum tannin content required to confer bird-resistance or other desirable agronomic characteristics is required before high throughput, commercial processing of high-tannin sorghum would be viable.