Enhancing the nutritional value of sorghum grains bred for northern Europe through processing: A perspective on phenolic bioaccessibility and protein digestibility

The effect of dehulling and cooking on the in vitro digestibility, and phenolic profiles was evaluated for four Dutch sorghum varieties (HD7 and HD19, Sorghum bicolor; and HD100 and HD101 Sorghum nigricans) bred in the Netherlands. Protein content ranged from 9 to 14 % and grains with black pericarp were more resistant to dehulling. Essential amino acids composition analysis showed that the lysine chemical score (∼0.6) was lower than that required for adults. Phenolic profiling by UHPLC-ESI-QTOF/MS allowed annotaion of 219 phenolic compounds, with flavonoids as the most representative class (91 %). Dehulling and genotype had stronger influence on the phenolic profiles than cooking; however, hydrothermal treatment was essential for the depolymerization of proanthocyanidin dimers and trimers. The combination of dehulling and boiling improved in vitro protein digestibility and increased in vitro bioaccessibility of key phenolic compounds. These processes are effective for developing high-quality sorghum-based products using Dutch varieties.