Effects of microwave pretreatment combined with fermentation and cooking on protein digestibility, mineral bioavailability, and functional properties of sorghum flour
The aim of this study was to investigate the effects of microwave heating (500 W) for different application times 15, 30 and 45 s on sorghum grain followed by fermentation and cooking on antinutritional factors (tannin content and polyphenols), Fe and Zn bioavailability, in vitro protein digestibility (IVPD) and flour properties. The results showed that microwave treatment alone or in combination with fermentation and cooking significantly altered the rheological properties and nutritional quality of sorghum flour. The IVPD of sorghum was improved with significant reduction of tannin and polyphenol contents after processing ( p < 0.05). Microwave alone or followed by processing cause a significant change in Zn availability, however, no changes were observed for Fe availability. Peak viscosity, trough, setback and final viscosity of sorghum flour increased significantly ( p < 0.05) after microwave heating, either alone or after processing. The textural profile and swelling power of the sorghum flour were also affected by the microwave treatments especially in combination with fermentation and cooking. The partial least squares (PLS) validation model revealed that microwave heating for 45 s followed by processing appears most promising to improve the nutritional and functional aspects of sorghum samples. Hence it could be explored further for the household food processing methods.