Parboiling of sorghum grains as a strategy to improve endosperm yield and mineral content of refined flours

The aims were (i) to optimize the parboiling/decorticating process by assessing the effects of parboiling soaking temperature (60–80？℃) and pearling time (4–6？min and 5.5–9.5？min for red and white sorghum) on endosperm yield and ash content, to obtain pregelatinized refined flours from parboiling sorghum (RF-PS) and (ii) to evaluate the final content of selected nutrients in RF-PS obtained in these optimal conditions. Endosperm yield decreased with the increase of pearling time, and a maximum around 70？℃ soaking temperature was observed. Ash content decreased with increasing soaking temperature and pearling time. The optimal conditions of soaking temperature–pearling time were 73.3？℃–4.8？min for red sorghum and 67.9？℃–8.6？min for white sorghum, considering maximum endosperm yield and ash content lower than 0.65？g/100？g. In RF-PS obtained under optimal conditions, protein, lipid, Cu, and free polyphenols were higher in red sorghum than white sorghum (10.16？±？0.62 vs. 9.42？±？0.61？g/100？g, 0.89？±？0.16 vs. 0.62？±？0.11？g/100？g, 2.08？±？0.21 vs. 1.88？±？0.20？mg/kg, 79.51？±？14.51 vs. 63.82？±？4.33？mg/100？g). Fe, Zn, Ca, and Na were higher in white sorghum than red sorghum (20.61？±？2.92 vs. 17.56？±？0.98？mg/kg, 11.94？±？0.84 vs. 9.58？±？1.65？mg/kg, 87.45？±？12.91 vs. 75.31？±？12.57？mg/kg, 129.62？±？9.03 vs. 102.69？±？28.34？mg/kg). No difference was observed in the contents of ash, Mg, and K. It was possible to improve endosperm yield using a parboiling process prior to decortication. In addition, this process contributes to increase the mineral content in RF-PS