Proximate Composition and Tannin Content of Whole Grain Sorghum Flour and Formulated Sorghum Rusks

Abstract

Sorghum (Sorghum bicolor (L.) Moench) is a climate-resilient, gluten-free cereal with considerable potential for food diversification, value addition and improved food and nutrition security. This study evaluated the proximate composition, tannin content of whole-grain sorghum flour and sorghum-based rusks to assess changes associated with processing and product formulation. Whole sorghum grains obtained from local farmers in Lesotho were cleaned, washed, dried and milled to produce whole-grain sorghum flour. The flour was subsequently used to formulate rusks with additional ingredients, including pumpkin, eggs, milk, margarine, raisins, sugar, salt and bicarbonate of soda. Proximate composition was determined using standard analytical methods, while tannin content was assessed. Significant differences (P≤0.05) were observed between sorghum flour and rusks for the measured proximate components. Sorghum flour contained higher moisture (10.90 g/100 g), carbohydrate (71.29 g/100 g), crude fibre (5.10 g/100 g) and tannin (3.90 g/100 g), whereas the rusks contained higher ash (2.14 g/100 g), fat (14.71 g/100 g), protein (16.65 g/100 g) and energy (435.51 kcal/100 g). The moisture content decreased to 6.50 g/100 g in the rusks, reflecting the drying effect of the baking process. Tannin content decreased from 3.90 to 3.30 g/100 g in the formulated rusks. The higher protein, fat and ash contents of the rusks are attributable primarily to the incorporation of additional ingredients, while moisture reduction is consistent with baking and drying effects. Overall, the findings demonstrate the potential of rusk production as a value-addition approach for improving the utilization of sorghum and developing convenient, lower-moisture and nutritionally enhanced cereal products. Sorghum-based value-added products may contribute to dietary diversification, food security and agro-processing development in sorghum-producing regions such as Lesotho.

Keywords: Sorghum; Sorghum bicolor; Value Addition; Proximate Composition; Tannin; Particle Size Distribution; Rusks; Agro-Processing

Citation

Pulane Nkhabutlane. Proximate Composition and Tannin Content of Whole-Grain Sorghum Flour and Formulated Sorghum Rusks. WebLog J Nutr Food Sci. wjnfs.2026.j1504. https://doi.org/10.5281/zenodo.23367700