Impact of superheated steam processing on amino acids, structure, and functionality of Proso millet proteins

Abstract

Proso millet proteins (PMP) can be used as an alternative to gluten-free protein sources to meet market demand. Due to its poor digestibility and functional properties, PMP commercial applications have become challenging. Hence, superheated steam (SHS) treatment was applied to PMP (at 130–140 °C for 3, 6, and 9 min), which led to a slight variation in essential amino acids over shorter treatment durations. Increased SHS treatment durations at 130 °C improved in vitro protein digestibility (90.52 %) by unfolding the native PMP structures supported by disulfide bonds and secondary structures (where α-helix and β-sheet structures reduced). Apart from water absorption capacity, 130°C-9 min treated PMP showed the highest improvement in functional properties. The 140 °C treated PMP for 6 and 9 min resulted in thinner SDS-PAGE band intensities, larger particle sizes, and compact structural orientation, potentially leading to decreased functional properties (due to the degradation of heat-sensitive amino acids, hydrogen bonds, covalent interactions and excessive oxidation). From the multivariate analysis, it is recommended that SHS treatment at 130 °C for 6–9 min can modify PMP and may be helpful in developing meat alternatives, emulsions, hybrid milk, and other beverages.