Gelatin cages: The formation and characterization of carriers for housing catalyst cargoes

•The mechanisms of single-step formation of hollow spheroidal protein particles were revealed.•The process of formation was mapped and characterized.•The morphology of the hollow spheroidal protein particles was investigated.•The effect of meso- and micro-porosity on uptake/release mechanism was mapped out.•Ag nanoparticles were entangled in the meso and micro-porosity and used as catalyst carriers.