MuscatineGrain Processing Corporation Grain Processing Corporation (GPC) is a leading manufacturer and worldwide marketer of corn-based products including maltodextrins, corn syrup solids, and starches for the food, pharmaceutical, and personal care markets; ethyl alcohol for beverage and industrial use; starches for the paper, corrugated box, textile, and wallboard industries; corn oil; animal feed ingredients , and pet care products . GPC is a privately owned company with a solid history and the vision for continued success in the future. Local, National, Worldwide... Naturally A combination