CHAPTER 10: Zein: Structure, Production, Film Properties and Applications

Zein is an alcohol-soluble, naturally occurring protein polymer obtained from corn. It is classified into four classes (α, β, γ and δ) according to solubility and α-zein is the most abundant. The α-zein has large amounts of hydrophobic residues such as leucine, proline, alanine, and phenylalanine that contribute to its hydrophobic properties. Corn gluten meal and distillers dried grains with ‘solubles’ are the major sources of zein for commercial production. Most methods use aqueous solutions of ethanol or isopropyl alcohol for zein extraction. Physical, chemical or enzymatic methods are employed to enhance functional properties (water solubility, foaming and emulsifying properties) of zein. Zein exhibits moderate film-forming properties however; films made from zein alone are brittle and need to be blended with plasicizers. Formation of zein films for food packaging has been extensively explored and its tensile strength is comparable with the wheat gluten films. Zein has a wide variety of food and non-food applications. In the food and confectionary industries, it is used for coating bakery products, candies and chocolates as well as for packaging of frozen and ready-to-eat foods. Zein is also being used for making plastics, fibres, adhesives, coatings, and binders.