As the name implies, hydrolyzed protein cat food is a formula for cat food produced with hydrolyzed protein. Protein chains are broken down into smaller segments or split into individual amino acids. It inhibits an allergic reaction in the cat by breaking apart the proteins and changing how the cat's body reacts to them. Recipes for hydrolyzed protein cat food are typically created for cats with food allergies or intolerances, while in regular cat food, the protein is not hydrolyzed.