TECHNOLOGY OF CEREALS Air classification has been applied to other cereal and legume fours with some success. A Whole grain rye four of 8.5% protein was separated into a fine fraction with 14.4% protein and a coarse fraction with 7. 3%. Sorghum flour fractions between Pounding 5% and 16.6% protein were prepared from parent fours of 5.7-7.0% protein. Starting with grits(which are derived from the higher protein horny parts of the grain) of 9.2-11.9% protein content, fractions between 6.8 and 18.9% protein fLotation Husk were obtained(Stringfellow and Peplinski, 1966) Protein shifting by air-classification has not met with success when attempted in rice. Three factors are held responsible for this: the smallness of the starch granules, the intimate dispersions of the protein bodies and the extreme vitreousness of the endosperm(Deobold, 1972) Sorghums and millets are considered together Flour and meal as they are both tropical cereals, the majority of FiG 6. 5 Schematic diagram of domestic processing of sorghum the processing of which remains in the hands of subsistence farmers. The grinding of flour is Water may be used during the continuing grind- performed by traditional manual methods which ing, as appropriate to the type of grain used. The occupy much of the day of the women. In the decorticated grain is separated from the bran by case of sorghum particularly, several industrial winnowing, after drying in the sun; or water may milling methods are in use. Because industrial be used to separate the components. Further scale operations are relatively new, these may pounding follows to reduce the size of the particles be regarded as somewhat experimental, no of decorticated grains Sieving is used to separate single method having yet been established as material that has been reduced sufficiently, from the standard. Several methods are described that needing further treatment in domestic processing several principles are schematically in Fig. 6. Drocess is illustrated the following text. It is noticeable that, even The simplicity of the involved, and these are similar to those used in The principles illustrated are the industrial systems 1. Use of attrition to break open the grain 2. Separation of endosperm from the surrounding Domestic processing 3. Use of water to aid the separation The techniques used have been in continuous 4. Sieving to select stocks fo use for hundreds of years. Although simple, the or appropriate processes are instructive, both in their own right, and because they reflect the methods from which Another principle, common to all milling pro- modern cereal processing has evolved. They are cesses, and illustrated by hand milling, is the hand operations in which wooden pestle and dependence of the method adopted on the nature mortar are used, the abrasive action of pounding of the varieties processed. variations include the on the washed grain freeing the outer pericarp hardness of the endosperm and the thickness of from the remainder of the grain (cf. Ch. 13). the pericarp Soft grains break into pieces duringwith 7.3%. Sorghum flour fractions between Pounding grits (which are derived from the higher protein, horny parts of the grain) of 9.2-11.9% protein I Winnowing or f Coatot ion Protein shifting by air-classification has not met with success when attempted in rice. Three factors are held responsible for this: the smallness 4 Further pounding