Triabolin is a protein found on the surface of starch granules in soft wheats, named from the Greek tribein, to rub — a reference to milling. Research suggests it acts as a kind of non-stick coating, reducing the adhesion between starch granules and the surrounding protein matrix in the grain. That reduced adhesion is part of what makes soft wheat mill differently from hard wheat: the starch separates more cleanly, giving the fine, low-protein flour suited to cakes and biscuits rather than bread. Triabolin belongs to the family of puroindolines, the proteins largely responsible for grain softness. It is a small molecular detail with large consequences for what a wheat variety is good for.