Effect of dehulling, fermentation, and roasting on the nutrient and anti-nutrient content of sorghum and pearl millet flour

Abstract

Sorghum and pearl millet contain anti-nutritional factors such as tannins and phytic acid, which limits their use in processed food products. Pre-treatment processes of these traditional grains such as dehulling, roasting, and fermentation, have potential to reduce the anti-nutritional factors. However, there is death in data on their efficacy. Therefore, this study aimed to evaluate the effect of dehulling, fermenting and roasting on the proximate, micronutrient and anti-nutritional content of sorghum and pearl millet flour from Zimbabwe. The grains were roasted, dehulled, fermented, and milled into flour. Four treatments namely, (1) unprocessed sorghum (control 1), (2) processed sorghum, (3) unprocessed pearl millet (control 2) and (4) processed pearl millet were prepared. The treatment samples were evaluated for proximate and mineral content using standard methods of analysis (AOAC, 2000) and inductively coupled plasma atomic emission spectrophotometry (ICP-OES) method, respectively. Phytates and tannins were measured using the UV Spectrophotometer method. The alkaloid content was determined gravimetrically. Data were analysed statistically using ANOVA at 95% probability. Sorghum processing i.e. dehulling, fermenting, roasting and milling significantly increased the protein content (from 15.0±0.08 to 20.0±3.98%) and ash content (from 3.6±0.05 to 4.2±0.52%) (p0.05). Similarly, the protein content of pearl millet significantly increased after processing (from 20.0 ±0.07 to 25±2.875) (p0.05). The magnesium content decreased significantly after processing sorghum (p0.05). The magnesium and sodium content decreased significantly after processing (p0.05). Processing of sorghum and pearl millet is recommended since it improves the nutritional composition and lowers anti-nutritional factors.