[Peeling of sorghum by a dry method: continuous and discontinuous methods]

A study was carried out wherein two dry dehulling sorghum grain methods, the continuous and discontinuous types, were quantitatively compared in a laboratory abrasive dehulling device. Reflectance values, expressed as dehulling percentage, the percentage of kernels removed, and of kernel cracking were evaluated. Graphs of the dehulled and removed percentages as function of the contrast time for each method, revealed that the continuous process was the most efficient of both procedures. Analysis of the broken kernels indicated a similar behavior for both methods. The macrocomponent and tannin variations as dehulling advanced, as well as the reflectance values were determined with the continuous method. Findings showed that the greater proportion of tannin, fiber and ashes has been removed at the 85% extraction rate. Thus, abrasion of grains above the 65% extraction rate is not convenient, since an excessive loss of nutrients is produced without any important decrease in polyphenolic pigments and of those imparting color to the sorghum grain milling products.