On using gliadin for micro- and nanocellular foams

Bio-derived, fully biodegradable closed-cell micro- and nanocellular foams from gliadin, an abundantly available wheat storage protein, were produced in a newly derived foaming procedure using nitrogen or carbon dioxide as blowing agent. First, dry gliadin powder or gliadin film was plasticized, resulting in a viscoelastic paste that was then subjected to an atmosphere of nitrogen or carbon dioxide in a high-pressure cell. Subsequent tempering, followed by a sudden release of pressure and cooling resulted in closed-cell micro- or nanocellular foams. Depending on the type of blowing agent and the processing parameters, the foam morphology was tunable. Foams prepared via the proposed procedure exhibit the smallest cell sizes, highest cell number density, and highest porosity ever reported for foaming of wheat proteins. The procedure is simple and low cost, possibly leading to a technical realization and constituting a promising new approach for utilization of unique natural potential, e. g. for high technical quality (short purpose) packaging, insulation, and application materials that are easily and environmentally friendly recyclable, and even edible.