The present invention relates to a process for producing protein microparticles in dilute organic acid solutions and in the absence of an alcohol such as ethanol. The microparticles are formed by dissolving a cereal prolamin protein in a concentrated organic acid solution with agitation and then diluting the solution with an aqueous solution. Protein microparticles having vacuoles are thus formed. The protein microparticles may be used to form powders, films, coatings, matrices, scaffolds and the like. Complete films can be formed from the protein microparticles of the invention.