Taking inspiration from nature, research has focused on developing microstructures, nanostructures, and cages constructed from proteins and peptides as appealing devices to compartmentalize and transfer agents and chemical reactions or synthesis. Long-chain peptide and protein cages are scarcely retrieved, and their fabrication is far from clear; nonetheless, they have the advantage of being rigid-chains of high molecular weight, affording diverse supramolecular structures. Here, we report the ability of long gelatin peptides to form monodisperse spheroidal cages. We examine a range of synthetic modality conditions that give rise to gelatin particles with dissimilar properties. Using an emulsion containing a self-organizing system generated by reaction-diffusion, we produce protein cages in a one-vessel process. Based on systematic physiochemical analyses, the upload and release of cargo stored within these cages are convincingly revealed to occur slightly dependently under the conditions of the surrounding environment. We have demonstrated that the gelatin cages entrap silver nanoparticles in their internal volume and in the three-dimensional housing created by the supramolecular structure, allowing to complete the reduction of 4-nitrophenol to 4-aminophenol.