A method of processing an initial starch containing gluten protein to produce a purified starch having less than 20 parts per million of a gluten protein (i.e., “gluten free”). A slurry of the unpurified starch is treated with an agent to degrade the gluten protein, and then the degraded gluten protein is removed, resulting in a slurry of the purified starch. The slurry of the purified starch is dried, resulting in the purified starch, and the purified starch is tested to confirm that the purified starch meets the standard for being gluten free. The starch is from a member of the tribe Triticeae (e.g., wheat, rye, barley, or triticale) or other plant starch that either naturally contains gluten protein or may be contaminated with gluten protein. The agent is selected from among acids, bases, alcohols, surfactants, proteases, chaotropic agents, reducing agents, and combinations thereof.
