Hordein is a prolamin storage protein primarily found in barley (Hordeum vulgare) grains, belonging to the gluten family of proteins. It constitutes a significant portion of barley's endosperm and plays a crucial role in seed development and nutrient storage. Chemically, hordein is a mixture of polypeptides rich in glutamine, proline, and other amino acids, making it similar to gliadin in wheat. It is insoluble in water due to its hydrophobic nature but dissolves in aqueous alcohols like 70% ethanol, which is used in extraction processes. Hordein is relevant in food science, brewing, and malting industries, as it contributes to the foam stability in beer and affects dough properties in baking. However, it is a known trigger for celiac disease and non-celiac gluten sensitivity in susceptible individuals, as it resists digestion and can elicit immune responses. Research from peer-reviewed sources, such as the Journal of Agricultural and Food Chemistry, indicates that hordein varies in molecular structure among barley varieties, with molecular weights typically ranging from 30,000 to 60,000 Da. Its properties make it a subject of study in allergenicity, protein engineering, and gluten-free food development. Hordein extraction often involves alcohol-based methods, and it denatures under heat or acidic conditions, losing its functional properties.