Microwave treatment increased protein digestibility of pigeon pea (Cajanus cajan) flour: Elucidation of underlying mechanisms.

Pigeon pea is rich in proteins but has low protein digestibility like other legumes. This work investigated the effects of processing, including soaking, grinding, ultrasound and microwave, on the protein digestibility of pigeon pea flour. Only microwave treatment significantly increased in vitro protein digestibility from 54.4 ± 2.5% to 71.6 ± 4.2%. SDS-PAGE showed that the most abundant proteins in all samples were the 7S vicilin subunits. After microwave treatment, the starch granular structures of pigeon pea flour changed to clusters, and protein secondary structures lost 5% β-sheet and gained 5% random coil, which contributed to the increased protein digestibility. Microwave decreased protein water solubility from 94.4 ± 0.8% to 48.1 ± 6.5% and increased the disulfide bond content by 42%. The increased protein digestibility is attributable to the relatively reduced particle size (166.6 ± 38.6 nm) and increased zeta potential (-35.2 ± 2.6 mV) of the microwave-treated sample. Therefore, microwave is a promising approach for increasing pigeon pea flour protein quality and utilisation.