Zein ( ) is a class of prolamine

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

found in

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

. It is usually manufactured as a powder from corn gluten meal. Zein is one of the best understood plant proteins.Momany, Frank A.; Sessa, David J.; Lawton, John C.; Selling, Gordon W.; Hamaker, Sharon A. H.; and Willett, Julious L. "Structural Characterization of A-Zein" December 27, 2005, ''J. Agric. Food Chem.'' Pure zein is clear, odorless, tasteless, hard, water-insoluble, and edible, and it has a variety of industrial and food uses.Lawton, John W.
Zein: A History of Processing and Use
, November 1, 2002, American Association of Cereal Chemists

Commercial uses

Historically, zein has been used in the manufacture of a wide variety of commercial products, including coatings for paper cups, soda bottle cap linings, clothing fabric,Commission on Life Sciences
Biobased Industrial Products: Research and Commercialization Priorities
2002. buttons, adhesives, coatings and binders. The dominant historical use of zein was in the textile fibers market where it was produced under the name "Vicara". With the development of synthetic alternatives, the use of zein in this market eventually disappeared. By using

electrospinning Electrospinning is a fiber production method that uses Electrostatics, electrical force (based on electrohydrodynamic principles) to draw charged threads of polymer solutions for producing nanofibers with diameters ranging from nanometers to mi ...

, zein fibers have again been produced in the lab, where additional research will be performed to re-enter the fiber market.Miyoshi, T., Toyohara, H., Minematsu, H.
Preparation of ultrafine fibrous zein membranes via electrospinning
, ''Polymer International'' Vol. 54, no. 8, 2005.Selling, G., Biswas, A., Patel, A., Walls, D., Dunlap, C., Wei, Y.
Impact of Solvent on Electrospinning of Zein and Analysis of Resulting Fibers
, ''Macromolecular Chemistry and Physics'' Vol. 208, no. 9, 2007. It can be used as a water and grease coating for

paperboard Paperboard is a thick paper-based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.30 mm, 0.012 in, or 12 Inch#Equivalents, points) than paper and has certain superior ...

s and allows recyclability.Parris, Nicholas; Sykes, Marguerite; Dickey, Leland C.; Wiles, Jack L.; Urbanik, Thomas J.; Cooke, Peter H.
Recyclable zein-coated kraft paper
, ''Progress in paper recycling'' Vol. 11, no. 3, May 2002. Zein's properties make it valuable in processed foods and pharmaceuticals, in competition with insect

shellac Shellac () is a resin secreted by the female Kerria lacca, lac bug on trees in the forests of India and Thailand. Chemically, it is mainly composed of aleuritic acid, jalaric acid, shellolic acid, and other natural waxes. It is processed and s ...

. It is now used as a coating for candy, nuts, fruit, pills, and other encapsulated foods and drugs. In the United States, it may be labeled as " confectioner's glaze" (which may also refer to shellac-based glazes) and used as a coating on bakery products or as "vegetable protein." It is classified as Generally Recognized as Safe (

GRAS Gras may refer to: People * Basile Gras (1836–1901), French firearm designer * Enrico Gras (1919–1981), Italian filmmaker * Felix Gras (1844–1901), Provençal poet and novelist * Laurent Gras (disambiguation) * N. S. B. Gras (1884–1956), ...

) by the U.S. Food and Drug Administration. For pharmaceutical coating, zein is preferred over food shellac, since it is all natural and requires less testing per the USP monographs. Zein can be further processed into

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

s and other bioplastic

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s, which can be extruded or rolled into a variety of plastic products.Lee, Richard
Multiple-use Corn zein-based Biodegradable Resins, Sheets, and Films are an attractive alternative to plastic
,

University of Illinois at Urbana-Champaign The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United States. Established in 1867, it is the f ...

.Lawton Jr., J.W.
Plasticizers for Zein:their Effect on Tensile Properties and Water Absorption of Zein Films
January 12, 2004, ''Cereal Chemistry''. With increasing environmental concerns about synthetic coatings and the current higher prices of hydrocarbon-based petrochemicals, there is increased focus on zein as a raw material for a variety of nontoxic and renewable polymer applications, particularly in the paper industry.Jabar, Anthony Jr; Bilodeau, Michael A.; Neivandt, David J.; Spender, Jonathan
Barrier Compositions and Articles Produced with the Compositions
, December 29, 2005, United States Patent (pending) Other reasons for a renewed interest in zein include concern about the landfill costs of plastics, and consumer interest in natural substances. There are also a number of potential new food industry applications. Researchers at the

and at William Wrigley Jr. Company have recently been studying the possibility of using zein to replace some of the

gum base Gum base is the non-nutritive, non-digestible, water-insoluble Mastication, masticatory delivery system used to carry Sugar substitute, sweeteners, Flavoring, flavors, and any other substances in chewing gum and bubble gum. It provides all the basi ...

in chewing gum.McGowan B.A., Padua G.W., and Lee S-Y.
Formulation of Corn Zein Chewing Gum and Evaluation of Sensory Properties by the Time-Intensity Method
, September, 2005, ''Journal of Food Science''. They are also studying medical applications such as using the zein molecule to "carry biocompounds to targeted sites in the human body".Picklesimer, Phyllis.

"

. There are a number of potential food safety applications that may be possible for zein-based packaging according to several researchers. A military contractor is researching the use of zein to protect MRE food packages.Bertrand, Kate,
Military packages put technology to the test
" September 2005 Other packaging/food safety applications that have been researched include frozen foods,Padua, Graciela W., Rakotonirainy, Andrianaivo, and Wang, Qin

,

ready-to-eat chicken,Janes M.E.; Kooshesh S.; Johnson M.G.
Control of Listeria monocytogenes on the Surface of Refrigerated, Ready-to-eat Chicken Coated with Edible Zein Film
September, 2002, ''Journal of Food Science''. and cheese and liquid eggs.Dawson, Paul
Packaging Films Fight Bacteria and Help the Environment

Clemson University Clemson University () is a Public university, public Land-grant university, land-grant research university near Clemson, South Carolina, United States. - The blue-shaded pattern denotes university property. This shows Clemson University is ''out ...

Food researchers in Japan have noted the ability of the zein molecule to act as a water barrier.Qiangxian Wu, Hiroshi Sakabe and Seiichiro Isobe
Studies on the toughness and water resistance of zein-based polymers by modification
June, 2003, National Food Research Institute, Japan. While there are numerous existing and potential uses for zein, the main barrier to greater commercial success has been its historic high cost until recently. Zein pricing is now very competitive with food shellac. Zein may be extracted as a byproduct in the manufacturing process for

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

Core, Jim.
Corn Protein Could Reduce Ethanol Production Costs
" April 15, 2002,

United States Department of Agriculture The United States Department of Agriculture (USDA) is an executive department of the United States federal government that aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and producti ...

Agricultural Research Service The Agricultural Research Service (ARS) is the principal in-house research agency of the United States Department of Agriculture (USDA). ARS is one of four agencies in USDA's Research, Education and Economics mission area. ARS is charged with ext ...

. or in new off-shore manufacture.

Gene family

Alpha-prolamins are the major

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

storage protein Storage proteins serve as biological reserves of metal ions and amino acids, used by organisms. They are found in plant seeds, egg whites, and milk. Ferritin is an example of a storage protein that stores iron. Iron is a component of heme, which ...

s of

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of the grass tribe

Andropogoneae The Andropogoneae, sometimes called the sorghum tribe, are a large tribe of grasses (family Poaceae) with roughly 1,200 species in 90 genera, mainly distributed in tropical and subtropical areas. They include such important crops as maize (corn), ...

. They are unusually rich in glutamine, proline, alanine, and

leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-Car ...

residues and their

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is cal ...

s show a series of

tandem repeat In genetics, tandem repeats occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other, e.g. ATTCG ATTCG ATTCG, in which the sequence ATTCG is repeated three times. Several protein ...

s presumed to be the result of multiple intragenic

duplication Duplication, duplicate, and duplicator may refer to: Biology and genetics * Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known ...

. In ''Zea mays'' (Maize), the 22 kDa and 19 kDa zeins are encoded by a large multigene family and are the major seed storage

s accounting for 70% of the total zein fraction.

Structurally A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

the 22 kDa and 19 kDa zeins are composed of nine adjacent, topologically antiparallel

helices A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smoothness (mathematics), smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as ...

clustered within a distorted

cylinder A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

. The 22 kDa alpha-zeins are encoded by 23

genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

; twenty-two of the members are found in a roughly tandem array forming a dense

gene cluster A gene cluster is a group of two or more genes found within an organism's DNA that encode similar peptide, polypeptides or proteins which collectively share a generalized function and are often located within a few thousand base pairs of each othe ...

. The expressed

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s in the cluster are interspersed with nonexpressed

s. Some of the expressed genes differ in their

transcriptional regulation In molecular biology and genetics, transcriptional regulation is the means by which a cell regulates the conversion of DNA to RNA ( transcription), thereby orchestrating gene activity. A single gene can be regulated in a range of ways, from al ...

. Gene amplification appears to be in blocks of genes explaining the rapid and compact expansion of the cluster during the

evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

of maize. p.335

Other biodegradable polymers

Cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coate ...

Plastarch material Plastarch Material (PSM) is a biodegradable, thermoplastic resin. It is composed of starch combined with several other biodegradable materials. The starch is modified in order to obtain heat-resistant properties, making PSM one of few bioplastic ...

* Poly-3-hydroxybutyrate *

Polycaprolactone Polycaprolactone (PCL) is a synthetic, semi-crystalline, biodegradable polyester with a melting point of about 60 °C and a glass transition temperature of about −60 °C. The most common use of polycaprolactone is in the production ...

Polyglycolide Polyglycolide or poly(glycolic acid) (PGA), also spelled as polyglycolic acid, is a biodegradable, thermoplastic polymer and the simplest linear, aliphatic polyester. It can be prepared starting from glycolic acid by means of polycondensation or ...

Polylactic acid Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a plastic material. As a thermoplastic polyester (or polyhydroxyalkanoate) it has the backbone formula or . PLA is formally obtained by condensation of lactic acid with ...

References

External links

{{InterPro content, IPR002530 Seed storage proteins Food additives Biodegradable plastics Protein families