Residual Polyphenols, Phytate and In-vitro ProteinDigestibility of Extruded Sorghum-BambaraGroundnut Blends

摘要

Aim: This study was designed and implemented to produce instant breakfast cereals from the blends of sorghum and Bambara groundnut flour through extrusion cooking as a strategy to reduce phytic acid and polyphenol and improve the protein digestibility and solubility.Methodology: In this study, different blends of Bambara groundnut (10%, 20% and 30%) and sorghum flour were extruded at 20%, 22.5% and 25% moisture levels and 120°C, 140°C and 160°C barrel temperatures using a single-screw extruder. Response surface methodology with central composite face-centered design (CCFD) was used to model the residual phytic acid and polyphenols, protein solubility and protein digestibility of the extrudates.Results: Increasing the barrel temperature caused a reduction in protein solubility, residual polyphenols and phytic acid but increased the in vitro protein digestibility of the extrudates. The coefficients of determination (R~(2)) were 0.96, 0.83, 0.95 and 0.94 for polyphenols, phytic acid, protein solubility and protein digestibility respectively with non-significant lack of fit in all cases. Barrel temperature had the most effect on the responses.Conclusion: Extrusion cooking in combination with dehulling significantly increased the protein digestibility of sorghum-Bambara groundnut extrudates. The second order polynomial was found appropriate for the prediction of polyphenols, phytic acid and protein digestibility of the sorghum-Bambara groundnut extrudates. The optimum levels of the response variables attainable were 11.32%, 70.0%, 48 mg/100 g and 63.11 mg/100 g respectively for protein solubility, digestibility, residual polyphenols and phytate content.