Modeling Mineral Profile of Extruded Sorghum Bambara Groundnut Breakfast Cereals

Aims: This study was designed to assess the effect of Bambara groundnut flour, feed moisture and barrel temperature on the mineral profile of extruded sorghum-Bambara groundnut blends and the possible mineral contribution of the products to human nutrition.

Study Design: A central composite face-centered design (CCFCD) with response surface methodology (RSM) was used. Feed composition, feed moisture and barrel temperature at three levels of -1, 0 and +1 for each variable, was used to model the mineral composition of the sorghum-Bambara groundnut extrudates. A second order polynomial was used to fit the regression equation.

Methodology: Sorghum flour was blended with Bambara groundnut flour in varying proportions. Samples were extruded at 20 to 25% feed moisture and 120 to 160°C barrel temperature. Mineral analysis was performed using atomic absorption spectrophotometer (AAS). Statistical analysis was done using MINITAB version 14 statistical software.

Results: The calcium, zinc, phosphorus and potassium contents of all extrudates increased as the amount of Bambara groundnut flour in the feed increased. Feed composition had a significantly positive effect on the mineral content of the sorghum-Bambara groundnut extrudates. The coefficients of determination (R2) were 0.92, 0.81, 0.98, 0.96 and 0.97 for calcium, iron, zinc, phosphorus and potassium respectively with high values of adjusted R2 values. Plots of residuals against fitted values indicated adequacy of the empirical models.

Conclusion: The mineral contents of the extrudates generally increased with increases in Bambara groundnut flour in the feed. It was therefore concluded that blends of sorghum and Bambara groundnut flour can be used for production of instant (extruded) breakfast cereals to improve their mineral contents. The second order model was found appropriate for the prediction of the mineral profile of the extrudates.