Zein: the industrial protein from corn

Zein is the major storage protein of corn and comprises ≈45–50% of the protein in corn. It was first identified in 1897, based on its solubility in aqueous alcohol solutions. Zein isolate is not used directly for human consumption due to its negative nitrogen balance and poor solubility in water. Current zein manufacture is limited to ≈500 tonnes per year from corn gluten meal. Zein sells for ≈US$10–40 per kilogram, depending on purity. The ability of zein and its resins to form tough, glossy, hydrophobic grease-proof coatings and their resistance to microbial attack have been of commercial interest. Potential applications of zein include use in fiber, adhesive, coating, ceramic, ink, cosmetic, textile, chewing gum and biodegradable plastics. These new applications of zein appear promising, but requires the development of low-cost manufacturing methods. This paper reviews the present status of the chemistry, properties, uses and methods of manufacturing zein. The characteristics of zein are discussed in terms of its composition, structure, solubility in various solvents and gelation properties.