Zein is a class of

prolamine Prolamins are a group of plant storage proteins having a high proline amino acid content. They are found in plants, mainly in the seeds of cereal grains such as wheat (gliadin), barley (hordein), rye (secalin), corn (zein), sorghum (kafirin), and ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

found in

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

. It is usually manufactured as a powder from

corn gluten meal Corn gluten meal is the principal protein of corn (maize) endosperm consisting mainly of zein and glutelin. It is a byproduct of corn processing that has historically been used as an animal feed. Despite the name, corn gluten does not contain true ...

. 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, American Chemical Society 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 Cereals & Grains Association (formerly AACC International, formerly the American Association of Cereal Chemists) is a non-profit professional organization of members who are specialists in the use of cereal grains in foods. Founded in 1916, they ...

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 electric force to draw charged threads of polymer solutions or polymer melts up to fiber diameters in the order of some hundred nanometers. Electrospinning shares characteristics of both elec ...

, 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#equivalences, points) than paper and has certain ...

s and allows recyclability. Zein's properties make it valuable in processed foods and pharmaceuticals, in competition with insect shellac. 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 Resinous glaze is an alcohol-based solution of various types of food-grade shellac. The shellac is derived from the raw material sticklac, which is a resin scraped from the branches of trees left from when the small insect, ''Kerria lacca'' (also k ...

" (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) 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 In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...

s and other bioplastic

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

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 (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Univ ...

.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 (such as PFOA) 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)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. 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 The Wm. Wrigley Jr. Company, known as the Wrigley Company, is an American multinational chewing gum (Wrigley's gum) company, based in the Global Innovation Center (GIC) in Goose Island, Chicago, Illinois. Wrigley's is wholly owned by Mars, In ...

have recently been studying the possibility of using zein to replace some of the gum base 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 A Meal, Ready-to-Eat (MRE) is a self-contained, individual field ration in lightweight packaging purchased by the United States Department of Defense for its service members for use in combat or field conditions where other food is not availab ...

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 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 (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

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 the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...

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 A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

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, whic ...

s of

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of the grass tribe Andropogoneae. They are unusually rich in glutamine, proline, alanine, and leucine 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 calle ...

s show a series of

tandem repeat Tandem repeats occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other. Several protein domains also form tandem repeats within their amino acid primary structure, such as armadil ...

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 corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, ...

clustered within a distorted

cylinder A cylinder (from ) 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 infin ...

. The 22 kDa alpha-zeins are encoded by 23

genes In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

; twenty-two of the members are found in a roughly tandem array forming a dense gene cluster. The expressed

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

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 alt ...

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

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

of maize. p.335

Other biodegradable polymers

* Cellophane *

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 bioplasti ...

Poly-3-hydroxybutyrate Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type ...

Polycaprolactone Polycaprolactone (PCL) is a biodegradable polyester with a low melting point of around 60 °C and a glass transition temperature of about −60 °C. The most common use of polycaprolactone is in the production of speciality polyure ...

* Polyglycolide *

Polylactic acid Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula or , formally obtained by condensation of lactic acid with loss of water (hence its name). It can also be prepared by rin ...

References

External links

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