Which protein acts like a binder, holding food together and adding a ‘stretch’ property, and is found naturally in some grains, including wheat, barley, and rye?

Gluten

The correct answer is Option (3) - Gluten

Gluten is the protein that acts like a binder, holding food together and adding a 'stretch' property. Gluten is found naturally in some grains, including wheat, barley, and rye. It consists of two main proteins: gliadin and glutenin. When flour is mixed with water, gluten forms, providing the elasticity and structure to the dough, which is essential for various baked goods like bread and pastries.