Physicochemical properties of kafirin protein and its applications as building blocks of functional delivery systems

Kafirin, the major storage protein from grain sorghum, belongs to the prolamin protein family with its characteristic properties of being soluble in aqueous alcohol solutions, high proline content and high yield of ammonia upon hydrolysis. Due to its inferior nutritional quality and poor digestive performance in the human digestive tract, research efforts in recent years have been directed to its applications as novel value-added biomaterials. Recent studies revealed its unique physical properties of high hydrophobicity, good solubility in aqueous alcohol and acetic acid, elongated conformation and the ability to self-assemble into biomaterials with controlled morphology. The present review summarized the current understanding of kafirin protein in terms of its extraction, composition, structure as well as self-assembly behavior. Recent applications utilizing kafirin as an ingredient in gluten-free formulations and as novel building block for functional delivery systems are discussed. Kafirin has shown promising potential as a gluten-free ingredient and a novel value-added biodegradable polymer. Further studies are required not only to overcome the challenges of large-scale kafirin production, but also to enrich our understanding of its structural changes in different solvents and its interactions with other components to broaden its application spectrum.