Physical, interfacial and foaming properties of different mung bean protein fractions

Mung bean is an upcoming source of plant proteins with good foaming properties. The relation between its foaming properties and interfacial properties has not received much attention and was addressed in this work. To this end, five different mung bean protein fractions were produced. First, a protein-rich flour was obtained using dry fractionation, which was further processed into a protein mixture using mild wet fractionation to remove starch granules and other insoluble components. The protein mixture was further treated by isoelectric point precipitation to obtain a globulin- and albumin-rich fraction. Finally, we used the protein nativity of the dry fractionated flour to create protein coacervate droplets via liquid-liquid phase separation of the proteins at slightly acidic pH. The protein-rich coacervate droplets were heated and cross-linked into gelled particles, or “protein colloids”. The interfacial and foam-stabilising properties of the flour and protein mixture were dominated by the globulins, producing a foam with a poor stability. Also, non-proteinaceous components, such as starch granules, phenols and phospholipids, seemed to reduce foam stability. Albumins formed substantially stiffer interfaces, leading to foams with a high stability. The highest foam stability was observed for the protein colloids, which we attribute to the formation of stiff interfacial layers and probably also pinning of the lamellae in the foams by the protein colloids. In summary, mung bean albumins were found to possess substantially better foaming properties than the globulins, but especially mung bean protein colloids are a promising candidate for a plant-based foam ingredient.