Plant-based ingredients
are key building blocks for future sustainable
advanced materials. Functionality is typically higher for highly purified
plant-based ingredients, but this is at the expense of their sustainability
value. Here, a method is introduced for creating a soft functional
material, with structural elements ranging from the nanometer to the
millimeter scale, directly from legume flours. Globulins from soy
and pea flours are extracted in their native state at acidic pH and
mixed with gum arabic, resulting in liquid–liquid phase separation
into a dilute phase and a viscoelastic complex coacervate. Interfacial
tensions of the coacervates, determined via AFM-based probing of capillary
condensation, are found to be very low (γ = 48.5 and 32.3 μN/m
for, respectively, soy and pea), thus promoting the deposition of
a shell of coacervate material around oil droplets. Despite the complex
nature of the starting material, the dependence of interfacial tensions
on salt concentrations follows a scaling law previously shown to hold
for model complex coacervates. Curing of the coacervate material into
a strong and purely elastic hydrogel is shown to be possible via simple
heating, both in bulk and as a shell around oil droplets, thus providing
proof of principle for the fabrication of precise core–shell
microcapsules directly from legume flours.