Which protein is found in grains?

The correct option is Gluten.

Explanation:
Gluten is a structural family of storage proteins (mainly composed of prolamins like gliadin and glutelins like glutenin) found naturally in cereal grains such as wheat, barley, rye, and spelt. It plays a crucial role in baking by giving elasticity to dough, helping it rise and retain its shape, and giving bread its characteristic chewy texture.

Analysis of Options:
• Gluten: Correct. It is the primary protein complex found in grains.
• Gum protein: Incorrect. Gums (like guar gum or xanthan gum) are complex carbohydrates (polysaccharides), not grain storage proteins.
• Delta protein: Incorrect. This is not a term used to classify grain storage proteins.
• Arginine: Incorrect. Arginine is an amino acid (a basic building block of proteins), not a complete protein molecule found as a grain matrix.

Therefore, Gluten is the protein found in grains.