The effect of different laboratory-scale sample preparation methods on the composition of sorghum (Sorghum bicolor L.) and millet (panicum miliaceum L.) milling fractions

Abstract

Sorghum and millet are widely used basic food materials in developing countries, but in developed countries their novel food applications were discovered. For their commercial use, no standardized methods are available yet to evaluate their quality as food materials. In this experiment, two different lab-scale procedure (grinding and sieving with or without decortication) were used to obtain flour samples from Hungarian millet and sorghum cultivars and the changes of chemical composition (protein, ash, fat, starch, dietary fiber content) and phytic acid concentration were determined and compared to commercial flours. Both sample processing methods facilitated the separation of the hull, thereby significantly decreased the antinutritive phytic acid concentrations to the same levels as in commercial flours. Decortication increased the flour yield (59-68 %) of millet, however, in case of sorghum cultivars, no difference in yield (29-35 %) was detected after decortication. In case of millet cultivars, sieving without decortication decreased the crude protein, fat, ash and dietary fiber concentrations in flour samples to a higher extent, whilst in case of sorghum, sieving after decortication had greater impact on the chemical composition of the flour. However, both millet and sorghum flours showed advantageous nutritional composition compared to wheat flour. In conclusion, for millet sieving supported by decortication was found to be a more efficient sample processing method, but in case of sorghum the effect of decortication was negligible, and the same results were obtained by simple grinding and sieving.