Zein
Encyclopedia
Zein is a class of prolamine protein
found in maize
. It is usually manufactured as a powder from corn gluten meal
.
, zein fibers have again been produced in the lab, where additional research will be performed to re-enter the fiber market. Pure zein is clear, odorless, tasteless, hard, water-insoluble, and edible, making it invaluable 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
" (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.
Zein can be further processed into resin
s and other bioplastic polymer
s, which can be extruded or rolled into a variety of plastic products. 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. 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 University of Illinois at Urbana-Champaign
and at William Wrigley Jr. Company have recently been studying the possibility of using zein to replace some of the gum base in chewing gum. They are also studying medical applications such as using the zein molecule to "carry biocompounds to targeted sites in the human body". 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. Other packaging/food safety applications that have been researched include frozen foods, ready-to-eat chicken, and cheese and liquid eggs. Food researchers in Japan have noted the ability of the zein molecule to act as a water barrier.
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. Some believe the solution is to extract zein as a byproduct in the manufacturing process for ethanol
or in new off-shore manufacture.
storage protein
s of species
of the grass tribe Andropogonea. They are unusually rich in glutamine, proline, alanine, and leucine
residues
and their sequence
s show a series of tandem repeat
s presumed to be the result of multiple intragenic duplication. In Zea mays (Maize), the 22 kDa and 19 kDa zeins are encoded by a large multigene family and are the major seed storage protein
s accounting for 70% of the total zein fraction. Structurally the 22 kDa and 19 kDa zeins are composed of nine adjacent, topologically antiparallel
helices
clustered within a distorted cylinder
. The 22 kDa alpha-zeins are encoded by 23 genes
; twenty-two of the members are found in a roughly tandem array forming a dense gene cluster. The expressed
gene
s in the cluster are interspersed with nonexpressed gene
s. Interestingly, some of the expressed
genes differ in their transcriptional regulation
. Gene amplification appears to be in blocks of genes explaining the rapid and compact expansion of the cluster during the evolution
of maize
.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
found in maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
. It is usually manufactured as a powder from corn gluten meal
Corn gluten meal
Corn gluten meal is a byproduct of corn processing that has historically been used as an animal feed. It can also be used as an organic herbicide.- Herbicide :...
.
Commercial uses
Zein is one of the best understood plant proteins and has a variety of industrial and food uses. Historically, it has been used in the manufacture of a wide variety of commercial products, including coatings for paper cups, soda bottle cap linings, clothing fabric, 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 electrospinningElectrospinning
Electrospinning uses an electrical charge to draw very fine fibres from a liquid. Electrospinning shares characteristics of both electrospraying and conventional solution dry spinning of fibers. The process does not require the use of coagulation chemistry or high temperatures to produce solid...
, zein fibers have again been produced in the lab, where additional research will be performed to re-enter the fiber market. Pure zein is clear, odorless, tasteless, hard, water-insoluble, and edible, making it invaluable in processed foods and pharmaceuticals, in competition with insect shellac
Shellac
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes , which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish...
. 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
Pharmaceutical glaze
Pharmaceutical glaze is an alcohol based solution of various types of food grade shellac. When used in food and confections, it is also known as confectioner's glaze, resinous glaze, pure food glaze and natural 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
Gras is a commune in the Ardèche department in southern France.-Population:-References:*...
) by the U.S. Food and Drug Administration.
Zein can be further processed into resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
s and other bioplastic polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s, which can be extruded or rolled into a variety of plastic products. 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. 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 University of Illinois at Urbana-Champaign
University of Illinois at Urbana-Champaign
The University of Illinois at Urbana–Champaign is a large public research-intensive university in the state of Illinois, United States. It is the flagship campus of the University of Illinois system...
and at William Wrigley Jr. Company have recently been studying the possibility of using zein to replace some of the gum base in chewing gum. They are also studying medical applications such as using the zein molecule to "carry biocompounds to targeted sites in the human body". 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. Other packaging/food safety applications that have been researched include frozen foods, ready-to-eat chicken, and cheese and liquid eggs. Food researchers in Japan have noted the ability of the zein molecule to act as a water barrier.
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. Some believe the solution is to extract zein as a byproduct in the manufacturing process for ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
or in new off-shore manufacture.
Gene family
Alpha-prolamins are the major seedSeed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
storage protein
Storage protein
Storage proteins are biological reserves of metal ions and amino acids, used by organisms. They are found in plant seeds, egg whites, and milk....
s of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of the grass tribe Andropogonea. They are unusually rich in glutamine, proline, alanine, and leucine
Leucine
Leucine is a branched-chain α-amino acid with the chemical formula HO2CCHCH2CH2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins...
residues
Residue (chemistry)
In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....
and their sequence
Sequence (biology)
A sequence in biology is the one-dimensional ordering of monomers, covalently linked within in a biopolymer; it is also referred to as the primary structure of the biological macromolecule.-See also:* Protein sequence* DNA sequence...
s show a series of tandem repeat
Tandem repeat
Tandem repeats occur in DNA when a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other. -Example:An example would be:in which the sequence A-T-T-C-G is repeated three times.-Terminology:...
s presumed to be the result of multiple intragenic duplication. In Zea mays (Maize), the 22 kDa and 19 kDa zeins are encoded by a large multigene family and are the major seed storage protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s accounting for 70% of the total zein fraction. Structurally the 22 kDa and 19 kDa zeins are composed of nine adjacent, topologically antiparallel
Antiparallel (biochemistry)
In biochemistry, two molecules are antiparallel if they run side-by-side in opposite directions or when both strands are complimentary to each other....
helices
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
clustered within a distorted cylinder
Cylinder (geometry)
A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...
. The 22 kDa alpha-zeins are encoded by 23 genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
; twenty-two of the members are found in a roughly tandem array forming a dense gene cluster. The expressed
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s in the cluster are interspersed with nonexpressed gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s. Interestingly, some of the expressed
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
genes differ in their transcriptional regulation
Transcriptional regulation
Transcriptional regulation is the change in gene expression levels by altering transcription rates. -Regulation of transcription:Regulation of transcription controls when transcription occurs and how much RNA is created...
. Gene amplification appears to be in blocks of genes explaining the rapid and compact expansion of the cluster during the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
of maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
.
Other biodegradable polymers
- CellophaneCellophaneCellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging...
- Plastarch materialPlastarch materialPlastarch Material 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 bioplastics capable of withstanding high temperatures...
- PolycaprolactonePolycaprolactonePolycaprolactone is a biodegradable polyester with a low melting point of around 60°C and a glass transition temperature of about −60°C. PCL is prepared by ring opening polymerization of ε-caprolactone using a catalyst such as stannous octoate. Recently a wide range of catalysts for the ring...
- PolyglycolidePolyglycolidePolyglycolide or 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 ring-opening polymerization. PGA has been known since 1954 as a tough fiber-forming polymer...
- Poly-3-hydroxybutyrate
- Polylactic acidPolylactic acidPoly or polylactide is a thermoplastic aliphatic polyester derived from renewable resources, such as corn starch , tapioca products or sugarcanes...
External links
- Oregon State UniversityOregon State UniversityOregon State University is a coeducational, public research university located in Corvallis, Oregon, United States. The university offers undergraduate, graduate and doctoral degrees and a multitude of research opportunities. There are more than 200 academic degree programs offered through the...
Food Resource: Zein - INVIZTM by POETPOET LLCPOET LLC is a U.S. biofuel company that specializes in the creation of bioethanol. The privately held corporation, which was originally called Broin Companies, is headquartered in Sioux Falls, South Dakota. In 2007, the Renewable Fuels Association named POET the largest U.S. ethanol producer,...