AgarFrom Wikipedia, the free encyclopedia

For other uses, see Agar (disambiguation).This article needs additional citations for verification.Please help improve this article by adding reliable references. Unsourced material may be challenged and removed.(October 2008)

Mizuyōkan - a popular Japanese red bean jelly made from agar

Agar or agar agar is a gelatinous substance derived from red algae. Historically and in a modern

context, it is chiefly used as an ingredient in desserts throughout Asia and also in the past century has

found extensive use as a solid substrate to contain culture medium for microbiological work. The

gelling agent is an unbranchedpolysaccharide obtained from the cell walls of some species of red

algae, primarily from the genera Gelidium and Gracilaria, or seaweed (Sphaerococcus euchema).

Commercially it is derived primarily from Gelidium amansii.

Agar (agar agar) can be used as a laxative, a vegetarian gelatin substitute, a thickener for soups,

in jellies, ice cream and other desserts, as a clarifying agent inbrewing, and for paper sizing fabrics.

Chemically, agar is a polymer made up of subunits of the sugar galactose. Agarpolysaccharides serve

as the primary structural support for the algae's cell walls.

Contents

 [hide]

1   Names

2   Structure

3   Properties

4   Microbiology

5   Motility assays

6   Molecular biology

7   Plant biology

8   Culinary

9   Other uses

10   See also

11   References

[edit]Names

The word "agar" comes from the Malay word agar-agar (meaning jelly). It is also known

as kanten, China grass, or Japanese isinglass. The various species of alga or seaweed from which

agar is derived are sometimes called Ceylon moss. Gracilaria lichenoides specifically is referred to

as agal-agal or Ceylon agar.[1]

In Malay and Indonesian, it is known as agar-agar. In Japanese, it is known as kanten (寒天) meaning

"cold weather," referring to the fact that it is harvested in the winter months. In Mandarin Chinese as

hǎicài (海菜) meaning "ocean vegetable", hǎizàoqióngzhī (海藻瓊脂) or dòngfěn (凍粉). In Taiwanese

Hokkien it is known as chhài-iàn (菜燕) meaning "vegetable swiftlet," i.e., similar in texture to the nest

of the edible-nest swiftlet used in bird's nest soup. In Korea, it is known as hancheon (한천). In

the Philippines, it is known as gulaman in Tagalog, Apayao,Bikol,

and Pangasinan, guraman in Ilokano and gurguraman in Sambali.[2] In Thai it is known as wóon (วุ้� �น).

In Tamil and Telugu it's calledpaal kasuv.

[edit]Structure

The structure of an agarose polymer.

Agar consists of a mixture of agarose and agaropectin. Agarose is a linear polymer,made up of the

repeating monomeric unit of agarobiose. Agarobiose is a disaccharide made up of D-galactose and

3,6-anhydro-L-galactopyranose. Its major differences from carrageenans are the presence of L-3,6-

anhydro-α-galactopyranose rather than D-3,6-anhydro-α-galactopyranose units and the lack of sulfate

groups. Agaropectin is a heterogeneous mixture of smaller molecules that occur in lesser amounts.

Their structures are similar but slightly branched and sulfated, and they may have methyl and pyruvic

acid ketal substituents. They gel poorly and may be simply removed from the excellent gelling agarose

molecules by using their charge. The quality of agar is improved by toe treatment that converts of any

L-galactose-6-sulfate to 3,6-anhydro-L-galactose.

The gel network of agarose contains double helices formed from left-handed threefold helices. These

double helices are stabilized by the presence of water molecules bound inside the double helical cavity

[508]. Exterior hydroxyl groups allow aggregation of up to 10,000 of these helices to form suprafibers.[3]

[edit]Properties

Agar exhibits hysteresis, melting at 85 °C (358 K, 185 °F) and solidifying from 32-40 °C (305-313 K,

90-104 °F).[4]

[edit]Microbiology

100mm diameter petri dishes containing agar jelly for bacterial culture

Main article: Agar plate

Nutrient agar is used throughout the world to provide a solid surface containing medium for the growth

of bacteria and fungi. Agar is typically sold commercially as a powder that can be mixed with water and

prepared similarly to gelatin before use as a growth medium. The basic agar formula can be used to

grow most of the microbes whose needs are known. More specific nutrient agars are available,

because some microbes prefer certain environmental conditions over others.

[edit]Motility assays

As a gel, an agarose medium is porous and therefore can be used to measure microorganism motility

and mobility. The gel's porosity is directly related to the concentration of agarose in the medium, so

various levels of effective viscosity (from the cell's "point of view") can be selected, depending on the

experimental objectives.

A common identification assay involves culturing a sample of the organism deep within a block of

nutrient agar. Cells will attempt to grow within the gel structure. Motile species will be able to migrate,

albeit slowly, throughout the gel and infiltration rates can then be visualized; whereas non-motile

species will only show growth along the now-empty path introduced by the invasive initial sample

deposition.

Another setup commonly used for measuring chemotaxis and chemokinesis utilizes the under-agarose

cell migration assay whereby a layer of agarose gel is placed between a cell population and a

chemoattractant. As a concentration gradient develops from the diffusion of the chemoattractant into

the gel, various cell populations requiring different stimulation levels to migrate can then be visualized

over time using microphotography as they tunnel upward through the gel against gravity along the

gradient.

[edit]Molecular biology

Agar is a heterogeneous mixture of two classes of polysaccharide: agaropectin and agarose.

[5] Although both polysaccharide classes share the same galactose-based backbone, agaropectin is

heavily modified with acidic side-groups, such as sulfate and pyruvate.

The neutral charge and lower degree of chemical complexity of agarose make it less likely to interact

with biomolecules and therefore agarose has become the preferred matrix for work with proteins and

nucleic acids. Gels made from purified agarose have a relatively large pore size, making them useful

for separation of large molecules, such as proteins and protein complexes >200 kilodaltons, as well as

DNA fragments >100 basepairs. Agarose has been used widely

for immunodiffusion and immunoelectrophoresis as the agarose fibers functions as an anchor for

immunocomplexes. Agarose is used generally as the medium for analytical

scaleelectrophoretic separation in agarose gel electrophoresis and for column-based preparative scale

separation as in gel filtration chromatography and affinity chromatography.

[edit]Plant biology

Physcomitrella patens plants growingaxenically in vitro on agar plates (Petri dish, 9 cm diameter).

Research grade agar is used extensively in plant biology as it is supplemented with a nutrient and

vitamin mixture that allows for seedling germination in petri dishes under sterile conditions (given that

the seeds are sterilized as well). Nutrient and vitamin supplementation for Arabidopsis thaliana is

standard across most experimental conditions. Murashige & Skoog (MS) nutrient mix and Gamborg's

B5 vitamin mix are generally used. A 1.0% agar/0.44% MS+vitamin dH20 solution is suitable for growth

media between normal growth temps.

The solidification of the agar within any growth media (GM) is pH-dependent, with an optimal range

between 5.4-5.7. Usually, the application of KOH is needed to increase the pH to this range. A general

guideline is about 600 µl 0.1M KOH per 250 ml GM. This entire mixture can be sterilized using the

liquid cycle of an autoclave.

This medium nicely lends itself to the application of specific concentrations of phytohormones etc. to

induce specific growth patterns in that one can easily prepare a solution containing the desired amount

of hormone, add it to the known volume of GM, and autoclave to both sterilize and evaporate off any

solvent that may have been used to dissolve the often polar hormones. This hormone/GM solution can

be spread across the surface of petri dishes sown with germinated and/or etiolated seedlings.

Experiments with the moss Physcomitrella patens, however, have shown that choice of the gelling

agent — agar or Gelrite - does influencephytohormone sensitivity of the plant cell culture.[6]

[edit]Culinary

Agar-Agar is a natural vegetable gelatin counterpart. White and semi-translucent, it is sold in packages

as washed and dried strips or in powdered form. It can be used to make jellies, puddings and custards.

For making jelly, it is boiled in water until the solids dissolve. One then adds sweetener, flavouring,

colouring, fruit or vegetables, and pours the liquid into molds to be served as desserts and

vegetable aspics, or incorporated with other desserts, such as a jelly layer on a cake.

Agar-agar is approximately 80% fiber, so it can serve as an intestinal regulator. Its bulk quality is

behind one of the latest fad diets in Asia, the kanten diet. Once ingested, kanten triples in size and

absorbs water. This results in the consumer feeling more full. Recently this diet has received some

press coverage in the United States as well. The diet has shown promise in obesity studies.[7]

One use of agar in Japanese cuisine is anmitsu, a dessert made of small cubes of agar jelly and

served in a bowl with various fruits or other ingredients. It is also the main ingredient in Mizuyōkan,

another popular Japanese food. (See very top image.) In Indian cuisine, agar agar is known as "China

grass" and is used for making desserts. In Burmese cuisine, a sweet jelly known as kyauk kyaw (ေ�ကျ�ကျ�ေ�ကြကျ[tʃaoʔtʃau]) is made from agar.

[edit]Other uses

Agar is used:

As an impression material in dentistry.

To make salt bridges for use in electrochemistry.

In formicariums as a transparent substitute for sand and a source of nutrition.

CarrageenanFrom Wikipedia, the free encyclopedia

Carrageenans or carrageenins (pronounced / ˌkærəˈ ɡ iːnənz/ , with a hard   g ) are a family of linear

sulfated polysaccharides which are extracted from red seaweeds.

Gelatinous extracts of the Chondrus crispus seaweed have been used as food additives for hundreds

of years.[1] Carrageenan is a vegetarianand vegan alternative to gelatin.

Contents

 [hide]

1   Properties

2   Production

o 2.1   Semi refined

o 2.2   Refined

o 2.3   Mixed processing

3   Uses

o 3.1   Sexual lubricant and microbicide

3.1.1   HSV

3.1.2   HPV

3.1.3   HIV

4   Health concerns

5   See also

6   References

[edit]Properties

The molecular structure of different types of carrageenan.This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged andremoved. (July 2009)

Carrageenans are large, highly flexible molecules which curl forming helicalstructures. This gives them

the ability to form a variety of different gels at room temperature. They are widely used in the food and

other industries as thickeningand stabilizing agents. A particular advantage is that they

are pseudoplastic—they thin under shear stress and recover their viscosity once the stress is

removed. This means that they are easy to pump but stiffen again afterwards.

All carrageenans are high molecular weight polysaccharides made up of repeating galactose units and

3,6 anhydrogalactose (3,6-AG), both sulfated and nonsulfated. The units are joined by alternating

alpha 1-3 and beta 1-4 glycosidic linkages.

There are three main commercial classes of carrageenan:

Kappa: strong, rigid gels. Gels with potassium ions, reacts with dairy

proteins. Mainly from Eucheuma cottonii.

Iota: soft gels. Gels with calcium ions. Produced mainly

from Eucheuma spinosum

Lambda: Does not gel, used to thicken dairy products. The most

common source is Gigartina from South America.

The primary differences which influence the properties of kappa, iota and lambda carrageenan are the

number and position of the ester sulfate groups on the repeating galactose units. Higher levels of ester

sulfate lower the solubility temperature of the carrageenan and produce lower strength gels, or

contribute to gel inhibition (lambda carrageenan).

Many red algal species produce different types of carrageenans during their developmental history.

For instance, the genus Gigartinaproduces mainly Kappa carrageenans during its gametophytic stage,

and Lambda carrageenans during its sporophytic stage. SeeAlternation of generations.

All are soluble in hot water, but in cold water only the Lambda form (and the sodium salts of the other

two) are soluble.

When used in food products, carrageenan has the EU additive E-number E407 or E407a when

present as "Processed eucheuma seaweed", and is commonly used as an emulsifier. When iota

carrageenan is combined with Sodium stearoyl lactylate (SSL) a synergistic effect is created, allowing

for stabilizing/emulsifying that is not obtained with any other type of carrageenan (kappa/lambda) or

with other emulsifiers (monodiglycerides, etc). Sodium stearoyl lactylate combined with iota

carrageenan is capable of producing emulsions under both hot and cold conditions using either

vegetable or animal fat.

[edit]Production

This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged andremoved. (July 2009)

Although carrageenans were introduced on an industrial scale in the 1930s, they were first used

in China around 600 BC (where Gigartinawas used) and in Ireland around 400 AD.[citation needed]

The largest producer in contemporary times is the Philippines, where cultivated seaweed produces

about 80% of the world supply.[citation needed] The most commonly used are Cottonii (Kappaphycus

alvarezii, K.striatum) and Spinosum (Eucheuma denticulatum), which together provide about three

quarters of the world production. These grow from the sea surface to a depth of about 2 metres. The

seaweed is normally grown on nylon lines strung between bamboo floats and harvested after three

months or so when each plant weighs around 1 kg.

The Cottonii variety has been reclassified as Kappaphycus cottonii by Maxwell Doty (1988), thereby

introducing the genus Kappaphycus, on the basis of the phycocolloids produced (namely kappa

carrageenan).[citation needed]

After harvest, the seaweed is dried, baled, and sent to the carrageenan manufacturer. There the

seaweed is ground, sifted to remove impurities such as sand, and washed thoroughly. After treatment

with hot alkali solution (e.g. 5-8% potassium hydroxide), the cellulose is removed from the

carrageenan by centrifugation and filtration. The resulting carrageenan solution is then concentrated

by evaporation. It is dried and ground to specification.

There are three types of processing:

[edit]Semi refined

This is only performed using Eucheuma cottonii or Eucheuma spinosum. The raw weed is first sorted

and crude contaminants removed by hand. The weed is then washed to remove salt and sand, and

then cooked in hot alkali to increase the gel strength. The cooked weed is washed, dried and

milled. Eucheuma spinosum undergoes a much milder cooking cycle as it dissolves quite readily. The

product is called semi refined carrageenan, Philippines natural grade or, in the USA, it simply falls

under the common carrageenan specification.[2]

[edit]Refined

The essential difference in the refining process is that the carrageenan is dissolved and filtered to

remove cell wall debris. The clear solution is then precipitated either by alcohol or by potassium

chloride.[3]

[edit]Mixed processing

A hybrid technology exists where weed is treated heterogeneously as in the semi refined process but

alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American

weeds and gives some of the cost benefits of semi refined processing, while allowing a wider ranges of

weeds to be processed. Oddly the naturally low cellulose levels in some South American weeds allows

them to be heterogeneously processed and still be sold under the EU refined specification.

[edit]Uses

Personal lubricant made from carrageenan.

Desserts , ice cream, cream, milk shakes, sweetened condensed

milks, sauces: gel to increase viscosity

Beer : clarifier to remove haze-causing proteins

Pâtés  and processed meat: Substitute fat to increase water retention

and increase volume

Toothpaste : stabilizer to prevent constituents separating

Fruit Gushers : ingredient in the encapsulated gel.

Fire fighting foam: thickener to cause foam to become sticky

Shampoo  and cosmetic creams: thickener

Air freshener gels

Marbling : the ancient art of paper and fabric marbling uses a

carrageenan mixture to float paints or inks upon; the paper or fabric is

then laid on it, absorbing the colors.

Shoe polish: gel to increase viscosity

Biotechnology : gel to immobilize cells/enzymes

Pharmaceuticals: used as an inactive excipient in pills/tablets

Carrageenan: used to thicken skim milk, in an attempt to emulate the

consistency of whole milk. This usage did not become popular. It is

used in some brands of soy milk

Diet sodas

Soy milk

Pet food

Alien  saliva (movie effects).

Personal lubricants

Lambda carrageenan is used in animal models of inflammation used

to test analgesics, because dilute carrageenan solution (1–2%)

injected subcutaneously causes swelling and pain.

Shaving ham sold at restaurants and commercial delis.

[edit]Sexual lubricant and microbicide

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (October 2009)

Studies at the Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland, United

States of America, suggest that carrageenans might function as a topical microbicide.

[edit]HSV

There are indications that a carrageenan-based gel may offer some protection against HSV-2

transmission by binding to the receptors on the herpes virus thus preventing the virus from binding to

cells. Research has shown that a carrageenan-based gel effectively prevented HSV-2 infection at a

rate of 85% in a mouse model.[4] Some personal and condom lubricants are already made with

carrageenan, and several of these products (such as Divine) were found to be potent HPV inhibitors in

the study (though others that listed carrageenan in their ingredients were not).[5] See Herpes simplex:

Polysaccharides

[edit]HPV

Laboratory studies have shown that carrageenans are extremely potent inhibitors of HPV infection in

vitro and in animal challenge models.[6]Clinical trial results announced at the 2010 International

Papillomavirus Conference held in Montreal, Canada indicate that a carrageenan-based personal

lubricant called Carraguard is effective for preventing HPV infection in women.[7] The clinical results

suggest that use of carrageenan-based personal lubricant products, such as Divine No 9,

BIOglide [8] or Oceanus Carrageenan [9] may likewise be effective for preventing HPV infection.

[edit]HIV

A phase 3 clinical trial by Population Council examined whether a carrageenan-based product known

as Carraguard was effective as a topical microbicide for blocking HIV infection in women.[4] The trial

ran from 2004 to 2007, with more than 4,000 South African women completing the study, but found no

statistical difference in infection between those who used the lubricant and those who did not.[10][11] The

trial did provide information about usage patterns, however, and showed that the gel is safe at least—

not increasing infection any more than the baseline or causing significant side effects. As such, they

expect to use it as a stable delivery vehicle for experimental antiretrovirals in future studies.

Concurrent studies in macaques found the same Carrageenan gels used in clinical trials to be effective

against SIV challenge. This was in direct contrast of in vitro findings, where the compound was found

to enhance HIV and SIV infections in various assays. Although compliance was believed to be one

issue in clinical versus animal trials, the high viscosity and controlled nature of animal-viral inoculations

(atraumatic introduction of virus using a French Catheter) may be why the latter animal study observed

a positive outcome.[12]

[edit]Health concerns

The Joint FAO/WHO expert committee on food additives states "that based on the information

available, it is inadvisable to use carrageenan or processed eucheuma seaweed in infant formulas".

[13] There is evidence from studies performed on rats, guinea pigs and monkeys which indicates that

degraded carrageenan (poligeenan) may cause ulcerations in the gastro-intestinal tract and gastro-

intestinal cancer.[14]Poligeenan is produced from carrageenan subjected to

high temperatures and acidity. The average carrageenan molecule weighs over 100,000 Da while

poligeenans have a molecular weight of less than 50,000 Da. A scientific committee working on behalf

of the European Commission has recommended that the amount of degraded carrageenan be limited

to a maximum of 5% (which is the limit of detection) of total carrageenan mass. Upon testing samples

of foods containing high molecular weight carrageens, researchers found no poligeenan.[15]

A recent publication[16] indicates that carrageenan induces inflammation in human intestinal epithelial

cells in tissue culture through aBCL10-mediated pathway that leads to activation of NFkappaB and IL-

8. Carrageenan may be immunogenic due to its unusual alpha-1,3-galactosidic link that is part of its

disaccharide unit structure. Consumption of carrageenan may have a role in intestinal inflammation

and possibly inflammatory bowel disease, since BCL10 resembles NOD2, mutations of which are

associated with genetic proclivity to Crohn's Disease.

Carrageenan is reported to interfere with macrophage activity.[17][18][19]

From Wikipedia, the free encyclopedia

Carrageenans or carrageenins (pronounced / ˌkærəˈ ɡ iːnənz/ , with a hard   g ) are a family of linear

sulfated polysaccharides which are extracted from red seaweeds.

Gelatinous extracts of the Chondrus crispus seaweed have been used as food additives for hundreds

of years.[1] Carrageenan is a vegetarianand vegan alternative to gelatin.

Contents

 [hide]

1   Properties

2   Production

o 2.1   Semi refined

o 2.2   Refined

o 2.3   Mixed processing

3   Uses

o 3.1   Sexual lubricant and microbicide

3.1.1   HSV

3.1.2   HPV

3.1.3   HIV

4   Health concerns

5   See also

6   References

[edit]Properties

The molecular structure of different types of carrageenan.This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged andremoved. (July 2009)

Carrageenans are large, highly flexible molecules which curl forming helicalstructures. This gives them

the ability to form a variety of different gels at room temperature. They are widely used in the food and

other industries as thickeningand stabilizing agents. A particular advantage is that they

are pseudoplastic—they thin under shear stress and recover their viscosity once the stress is

removed. This means that they are easy to pump but stiffen again afterwards.

All carrageenans are high molecular weight polysaccharides made up of repeating galactose units and

3,6 anhydrogalactose (3,6-AG), both sulfated and nonsulfated. The units are joined by alternating

alpha 1-3 and beta 1-4 glycosidic linkages.

There are three main commercial classes of carrageenan:

Kappa: strong, rigid gels. Gels with potassium ions, reacts with dairy

proteins. Mainly from Eucheuma cottonii.

Iota: soft gels. Gels with calcium ions. Produced mainly

from Eucheuma spinosum

Lambda: Does not gel, used to thicken dairy products. The most

common source is Gigartina from South America.

The primary differences which influence the properties of kappa, iota and lambda carrageenan are the

number and position of the ester sulfate groups on the repeating galactose units. Higher levels of ester

sulfate lower the solubility temperature of the carrageenan and produce lower strength gels, or

contribute to gel inhibition (lambda carrageenan).

Many red algal species produce different types of carrageenans during their developmental history.

For instance, the genus Gigartinaproduces mainly Kappa carrageenans during its gametophytic stage,

and Lambda carrageenans during its sporophytic stage. SeeAlternation of generations.

All are soluble in hot water, but in cold water only the Lambda form (and the sodium salts of the other

two) are soluble.

When used in food products, carrageenan has the EU additive E-number E407 or E407a when

present as "Processed eucheuma seaweed", and is commonly used as an emulsifier. When iota

carrageenan is combined with Sodium stearoyl lactylate (SSL) a synergistic effect is created, allowing

for stabilizing/emulsifying that is not obtained with any other type of carrageenan (kappa/lambda) or

with other emulsifiers (monodiglycerides, etc). Sodium stearoyl lactylate combined with iota

carrageenan is capable of producing emulsions under both hot and cold conditions using either

vegetable or animal fat.

[edit]Production

This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged andremoved. (July 2009)

Although carrageenans were introduced on an industrial scale in the 1930s, they were first used

in China around 600 BC (where Gigartinawas used) and in Ireland around 400 AD.[citation needed]

The largest producer in contemporary times is the Philippines, where cultivated seaweed produces

about 80% of the world supply.[citation needed] The most commonly used are Cottonii (Kappaphycus

alvarezii, K.striatum) and Spinosum (Eucheuma denticulatum), which together provide about three

quarters of the world production. These grow from the sea surface to a depth of about 2 metres. The

seaweed is normally grown on nylon lines strung between bamboo floats and harvested after three

months or so when each plant weighs around 1 kg.

The Cottonii variety has been reclassified as Kappaphycus cottonii by Maxwell Doty (1988), thereby

introducing the genus Kappaphycus, on the basis of the phycocolloids produced (namely kappa

carrageenan).[citation needed]

After harvest, the seaweed is dried, baled, and sent to the carrageenan manufacturer. There the

seaweed is ground, sifted to remove impurities such as sand, and washed thoroughly. After treatment

with hot alkali solution (e.g. 5-8% potassium hydroxide), the cellulose is removed from the

carrageenan by centrifugation and filtration. The resulting carrageenan solution is then concentrated

by evaporation. It is dried and ground to specification.

There are three types of processing:

[edit]Semi refined

This is only performed using Eucheuma cottonii or Eucheuma spinosum. The raw weed is first sorted

and crude contaminants removed by hand. The weed is then washed to remove salt and sand, and

then cooked in hot alkali to increase the gel strength. The cooked weed is washed, dried and

milled. Eucheuma spinosum undergoes a much milder cooking cycle as it dissolves quite readily. The

product is called semi refined carrageenan, Philippines natural grade or, in the USA, it simply falls

under the common carrageenan specification.[2]

[edit]Refined

The essential difference in the refining process is that the carrageenan is dissolved and filtered to

remove cell wall debris. The clear solution is then precipitated either by alcohol or by potassium

chloride.[3]

[edit]Mixed processing

A hybrid technology exists where weed is treated heterogeneously as in the semi refined process but

alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American

weeds and gives some of the cost benefits of semi refined processing, while allowing a wider ranges of

weeds to be processed. Oddly the naturally low cellulose levels in some South American weeds allows

them to be heterogeneously processed and still be sold under the EU refined specification.

[edit]Uses

Personal lubricant made from carrageenan.

Desserts , ice cream, cream, milk shakes, sweetened condensed

milks, sauces: gel to increase viscosity

Beer : clarifier to remove haze-causing proteins

Pâtés  and processed meat: Substitute fat to increase water retention

and increase volume

Toothpaste : stabilizer to prevent constituents separating

Fruit Gushers : ingredient in the encapsulated gel.

Fire fighting foam: thickener to cause foam to become sticky

Shampoo  and cosmetic creams: thickener

Air freshener gels

Marbling : the ancient art of paper and fabric marbling uses a

carrageenan mixture to float paints or inks upon; the paper or fabric is

then laid on it, absorbing the colors.

Shoe polish: gel to increase viscosity

Biotechnology : gel to immobilize cells/enzymes

Pharmaceuticals: used as an inactive excipient in pills/tablets

Carrageenan: used to thicken skim milk, in an attempt to emulate the

consistency of whole milk. This usage did not become popular. It is

used in some brands of soy milk

Diet sodas

Soy milk

Pet food

Alien  saliva (movie effects).

Personal lubricants

Lambda carrageenan is used in animal models of inflammation used

to test analgesics, because dilute carrageenan solution (1–2%)

injected subcutaneously causes swelling and pain.

Shaving ham sold at restaurants and commercial delis.

[edit]Sexual lubricant and microbicide

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (October 2009)

Studies at the Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland, United

States of America, suggest that carrageenans might function as a topical microbicide.

[edit]HSV

There are indications that a carrageenan-based gel may offer some protection against HSV-2

transmission by binding to the receptors on the herpes virus thus preventing the virus from binding to

cells. Research has shown that a carrageenan-based gel effectively prevented HSV-2 infection at a

rate of 85% in a mouse model.[4] Some personal and condom lubricants are already made with

carrageenan, and several of these products (such as Divine) were found to be potent HPV inhibitors in

the study (though others that listed carrageenan in their ingredients were not).[5] See Herpes simplex:

Polysaccharides

[edit]HPV

Laboratory studies have shown that carrageenans are extremely potent inhibitors of HPV infection in

vitro and in animal challenge models.[6]Clinical trial results announced at the 2010 International

Papillomavirus Conference held in Montreal, Canada indicate that a carrageenan-based personal

lubricant called Carraguard is effective for preventing HPV infection in women.[7] The clinical results

suggest that use of carrageenan-based personal lubricant products, such as Divine No 9,

BIOglide [8] or Oceanus Carrageenan [9] may likewise be effective for preventing HPV infection.

[edit]HIV

A phase 3 clinical trial by Population Council examined whether a carrageenan-based product known

as Carraguard was effective as a topical microbicide for blocking HIV infection in women.[4] The trial

ran from 2004 to 2007, with more than 4,000 South African women completing the study, but found no

statistical difference in infection between those who used the lubricant and those who did not.[10][11] The

trial did provide information about usage patterns, however, and showed that the gel is safe at least—

not increasing infection any more than the baseline or causing significant side effects. As such, they

expect to use it as a stable delivery vehicle for experimental antiretrovirals in future studies.

Concurrent studies in macaques found the same Carrageenan gels used in clinical trials to be effective

against SIV challenge. This was in direct contrast of in vitro findings, where the compound was found

to enhance HIV and SIV infections in various assays. Although compliance was believed to be one

issue in clinical versus animal trials, the high viscosity and controlled nature of animal-viral inoculations

(atraumatic introduction of virus using a French Catheter) may be why the latter animal study observed

a positive outcome.[12]

[edit]Health concerns

The Joint FAO/WHO expert committee on food additives states "that based on the information

available, it is inadvisable to use carrageenan or processed eucheuma seaweed in infant formulas".

[13] There is evidence from studies performed on rats, guinea pigs and monkeys which indicates that

degraded carrageenan (poligeenan) may cause ulcerations in the gastro-intestinal tract and gastro-

intestinal cancer.[14]Poligeenan is produced from carrageenan subjected to

high temperatures and acidity. The average carrageenan molecule weighs over 100,000 Da while

poligeenans have a molecular weight of less than 50,000 Da. A scientific committee working on behalf

of the European Commission has recommended that the amount of degraded carrageenan be limited

to a maximum of 5% (which is the limit of detection) of total carrageenan mass. Upon testing samples

of foods containing high molecular weight carrageens, researchers found no poligeenan.[15]

A recent publication[16] indicates that carrageenan induces inflammation in human intestinal epithelial

cells in tissue culture through aBCL10-mediated pathway that leads to activation of NFkappaB and IL-

8. Carrageenan may be immunogenic due to its unusual alpha-1,3-galactosidic link that is part of its

disaccharide unit structure. Consumption of carrageenan may have a role in intestinal inflammation

and possibly inflammatory bowel disease, since BCL10 resembles NOD2, mutations of which are

associated with genetic proclivity to Crohn's Disease.

Carrageenan is reported to interfere with macrophage activity.[17][18][19]

Alginic acidFrom Wikipedia, the free encyclopedia

Alginic acid

Other names[hide]

E400

Identifiers

CAS number 9005-32-7

EC number 232-680-1

ATC code A02 BX13

Properties

Molecular formula (C6H8O6)n

Molar mass 10,000 - 600,000

Appearance white to yellow, fibrous powder

Density 1.601 g/cm3

Acidity (pKa) 1.5-3.5

Except where noted otherwise, data are given for materials in their standard state (at 25   °C, 100   kPa)

Infobox references

Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell

walls of brown algae, where it, through binding water, forms a viscous gum. In extracted form it

absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water.[1]. Its colour

ranges from white to yellowish-brown. It is sold in filamentous, granular or powdered forms.

Contents

 [hide]

1   Structure

2   Forms

3   Uses

4   Sodium alginate

o 4.1   Uses

5   Potassium alginate

o 5.1   Uses

6   See also

7   External links

8   References

[edit]Structure

It is a linear copolymer with homopolymeric blocks of (1-4)-linked β-D-mannuronate (M) and its C-

5 epimer α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or

blocks.

The monomers can appear in homopolymeric blocks of consecutive G-residues (G-blocks),

consecutive M-residues (M-blocks), alternating M and G-residues (MG-blocks), or randomly organized

blocks.

[edit]Forms

Commercial varieties of alginate are extracted from seaweed, including the giant kelp Macrocystis

pyrifera, Ascophyllum nodosum, and various types of Laminaria. It is also produced by

two bacterial genera Pseudomonas and Azotobacter, which played a major role in the unravelling of

its biosynthesis pathway. Bacterial alginates are useful for the production of micro- or nanostructures

suitable for medical applications.[2]

[edit]Uses

Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such

as slimming aids, and in the manufacture of paper and textiles. It is also used

for waterproofing and fireproofing fabrics, as a gelling agent, and for thickening drinks, ice cream and

cosmetics.

Alginate is used in various pharmaceutical preparations such as Gaviscon, Bisodol, and Asilone.

Alginate is used extensively as animpression-making material in dentistry, prosthetics, lifecasting and

occasionally for creating positives for small-scale casting. It is also used in the food industry, for

thickening soups and jellies.

Calcium alginate is used in different types of medical products, including burn dressings that promote

healing and can be removed with less pain than conventional dressings.

Also, due to alginate's biocompatibility and simple gelation with divalent cations such as Ca2+, it is

widely used for cell immobilization andencapsulation.

Alginic acid (alginato) is also used in culinary arts, most notably in the "Esferificación" (Sphereification)

techniques of Ferran Adrià of El Bulliin Roses, Girona, where natural juices of fruits and vegetables

are encapsulated in bubbles that "explode" on the tongue when consumed. One of the most famous

examples of this use of alginic acid was when Ferran Adrià used alginic acid to make apple caviar.[3]

Due to its ability to absorb water quickly, alginate can be changed through a lyophilization process to a

new structure that has the ability to expand. It is used in the weight loss industry as an appetite

suppressant.

In March, 2010 researchers at Newcastle University announced that dietary alginates can reduce

human fat uptake by more than 75%.[4]

[edit]Sodium alginate

The chemical compound sodium alginate is the sodium salt of alginic acid. Its empirical formula is

NaC6H7O6. Sodium alginate is a gum, extracted from the cell walls of brown algae.

[edit]Uses

Its form as a flavorless gum, is used by the foods industry to increase viscosity and as an emulsifier. It

is also used in indigestion tablets and the preparation of dental impressions.

A major application for sodium alginate is in reactive dye printing, as as thickener for reactive dyestuffs

(such as the Procion cotton-reactive dyes) in textile screen-printing and carpet jet-printing. Alginates

do not react with these dyes and wash out easily, unlike starch-based thickeners.

Sodium alginate is a good chelator for pulling radioactive toxins such as iodine-131 and strontium-90

from the body which have taken the place of their non-radioactive counterparts.[5][6] It is also used

in immobilizing enzymes by inclusion.

As a food additive, sodium alginate is used especially in the production of gel-like foods. For example,

bakers' "Chellies" are often gelled alginate "jam." Also, the pimento stuffing in prepared cocktail olives

is usually injected as a slurry at the same time that the stone is ejected; the slurry is subsequently set

by immersing the olive in a solution of a calcium salt which causes rapid gelation by electrostatic

cross-linking.[citation needed] A similar process can be used to make "chunks" of everything from cat food

through "reformed" ham or fish to "fruit" pieces for pies. It has the E-number 401.

Nowadays it is also used in the biological experiments for the immobilization of cells to obtain

important products like alcohols, organic acids,etc.

In recent years sodium alginate has been used in molecular gastronomy at some of the best

restaurants in the world. Ferran Adria pioneered the technique and it has since been used by chefs

such as Grant Achatz and Heston Blumenthal. Sodium alginate is combined with calcium lactate or

similar compound to create spheres of liquid surrounded by a thin jelly membrane.

[edit]Potassium alginate

Potassium alginate is a chemical compound that is the potassium salt of alginic acid. It is an extract

of seaweed. Its empirical chemical formula is KC6H7O6.

[edit]Uses

Potassium alginate is widely used in foods as a stabilizer, thickener, and emulsifier.

Its use as a pharmaceutical excipient is currently limited to experimental hydrogel systems.

The viscosity, adhesiveness, elasticity, stiffness, and cohesiveness of potassium alginate hydrogels

have been determined and compared with values from a range of other hydrogel-forming materials.

The effect of calcium ions on the rheological properties of procyanidin hydrogels containing potassium

alginate and intended for oral administration has also been investigated.

ChitosanFrom Wikipedia, the free encyclopedia

This article's introduction section may not adequately summarize its contents. To comply with Wikipedia's lead section guidelines, please consider expanding the lead to provide an accessible overview of the article's key points. (September 2009)

Chitosan

Other names[hide]

Poliglusam

Identifiers

CAS number 9012-76-4

SMILES  [show]

Related compounds

Related compounds D-glucosamine and N-Acetylglucosamine(monomers)

Except where noted otherwise, data are given for materials in theirstandard state (at 25 °C, 100 kPa)

Infobox references

Chitosan (pronounced /ˈkaɪtɵsæn/) is a linear polysaccharide composed of randomly distributed β-(1-

4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). It has a

number of commercial and possible biomedical uses.

Contents

 [hide]

1   Manufacture and properties

2   Usage

o 2.1   Agricultural & Horticultural use

2.1.1   Natural Biocontrol & Elicitor

o 2.2   Water Filtration

o 2.3   Industrial use

o 2.4   Biomedical use

o 2.5   Claimed health benefits

3   Medical Research

4   See also

5   References

6   External links

[edit]Manufacture and properties

Commercial chitosan is derived from the shells of shrimp and other sea crustaceans, includingPandalus borealis,

pictured here.[1]

Chitosan is produced commercially by deacetylation of chitin , which is the structuralelement in

the exoskeleton of crustaceans (crabs, shrimp, etc.) and cell walls of fungi. The degree of

deacetylation (%DD) can be determined by NMR spectroscopy, and the %DD in commercial chitosans

is in the range 60-100 %.

The amino group in chitosan has a pKa value of ~6.5, thus, chitosan is positively charged and soluble

in acidic to neutral solution with a charge density dependent on pH and the %DA-value. This makes

chitosan a bioadhesive which readily binds to negatively charged surfaces such as mucosal

membranes. Chitosan enhances the transport of polar drugsacross epithelial surfaces, and

is biocompatible and biodegradable. Purified qualities of chitosans are available

for biomedical applications.

Chitosan and its derivatives such as trimethylchitosan (where the amino group has been trimethylated)

have been used in non-viral gene delivery. Trimethylchitosan, or quaternised chitosan, has been

shown to transfect breast cancer cells; with increased degree of trimethylation increasing the

cytotoxicity and at approximately 50% trimethylation the derivative is the most efficient at gene

delivery. Oligomeric derivatives (3-6 kDa) are relatively non-toxic and have good gene delivery

properties.[2]

[edit]Usage

[edit]Agricultural & Horticultural use

[edit]Natural Biocontrol & Elicitor

In agriculture, chitosan is used primarily as a natural seed treatment and plant growth enhancer, and

as a ecologically friendly biopesticide substance that boosts the innate ability of plants to defend

themselves against fungal infections.[3] The natural biocontrol active ingredient, chitin/chitosan, are

found in the shells of crustaceans, such as lobsters, crabs, and shrimp, and many other organisms

including insects andfungi. It is one of the most abundant bio-gradable materials in the world.

Degraded molecules of chitin/chitosan exist in soil and water. Chitosan applications for plants and

crops are regulated by the EPA and the USDA National Organic Program regulates its use on organic

certified farms and crops.[4] EPA approved bio-degradable chitosan products are allowed for use

outdoors and indoors on plants and crops grown commercially and by consumers.[5] The natural

biocontrol ability of chitosan should not be confused with the effects of fertilizers or pesticides upon

plants or the environment. Chitosan active biopesticides represent a new tier of cost effective

biological control of crops for agriculture and horticulture.[6]

File:YEA! treated broccoli.JPG

Day 30: non-treated broccoli vs. YEA! (chitosan) treated broccoli(Research Trial by Colorado State University)

The biocontrol mode of action of chitosan elicits natural innate defense responses within plant to resist

against insects, pathogens, and soil borne diseases when applied to foliage or the soil.[7] Chitosan

increases photosynthesis, promotes and enhances plant growth, stimulates nutrient uptake, increases

germination and sprouting, and boosts plant vigor. When used as seed treatment or seed coating on

cotton, corn, seed potatoes, soybean, sugar beet, tomato, wheat and many other seeds it elicits

aninnate immunity response in developing roots which destroy parasitic cyst nematodes without

harming beneficial nematodes and organisms.[8][9] Agricultural applications of chitosan can reduce

environmental stress due to drought and soil deficiencies, strengthen seed vitality, improve stand

quality, increase yields, and reduce fruit decay of vegetables, fruits and citrus crops (see photo right).

[10] Horticultural applications of chitosan increases blooms, extends the life of cut flowers and

Christmas trees.[11] The US Forest Service has conducted research on chitosan to control pathogens in

pine trees [12].[13] and chitosan's ability to increase pine tree resin pitch-out flow by 40% to resist pine

beetle infestation.[14]

NASA life support GAP technology with untreated beans (left tube) and ODC chitosan biocontrol treated beans

(right tube) returned from the Mir space station aboard the space shuttle – September 1997 [15]

Chitosan has a rich history of being researched for applications in agriculture and horticulture dating

back to the 1980s.[16] By 1989 Bentech Labs patented chitosan salt solutions applied to crops for

improved freeze protection or to crop seed for seed priming.[17] Shortly thereafter Bentech's chitosan

salt received the first ever biopesticide label from the EPA. Numerous other chitosan patents for plants

soon followed. Chitosan applications to protect plants have been used in space as well. NASA first

flew a chitosan experiment to protect adzuki beans grown aboard the space shuttle and Mir space

station in 1997 (see photo left).[18] NASA results revealed chitosan induces increased growth (biomass)

and pathogen resistance due to elevated levels of beta 1-3 glucanase enzymes within plant cells.

NASA confirmed chitosan elicits the same effect in plants on earth.[19] Over 20 years of R&D by

DuPont/ConAgra Ventures (DCV) and AgriHouse Inc have gone into developing non-toxic low

molecular weight chitosan polymer solutions safe enough for broad spectrum agricultural and

horticultural use.[20][21] In 2008, AgriHouse Inc, Denver [Berthoud], Colorado, was granted EPA natural

broad spectrum elicitor status for YEA! Yield Enhancing Agent, a liquid solution containing an ultra low

molecular active ingredient of 0.25% chitosan.[22] YEA! is a next generation natural chitosan elicitor

solution for agriculture and horticultural and was granted an amended label for foliar and irrigation

applications by the EPA in June, 2009. A milliliter of YEA! contains over 14.4 X 10¹³ bio-active low

molecular weight chitosan molecules and it is 600 times more effective than common chitosan.

[23] Given its low potential for toxicity and its abundance in the natural environment, chitosan does not

harm people, pets, wildlife, or the environment when used according to label directions.[24] Agricultural

chitosan facts are located on USDA and EPA web sites.[25][26]

[edit]Water Filtration

Chitosan can also be used in water processing engineering as a part of a filtration process. Chitosan

causes the fine sediment particles to bind together and is subsequently removed with the sediment

during sand filtration. Chitosan also removes phosphorus, heavy minerals, and oils from the water.

Chitosan is an important additive in the filtration process. Sand filtration apparently can remove up to

50% of the turbidityalone while the chitosan with sand filtration removes up to 99% turbidity.

[27] Chitosan has been used to precipitate caseins from bovine milk and cheese making [1] [2]

Chitosan is also useful in other filtration situations, where one may need to remove suspended

particles from a liquid. Chitosan, in combination with bentonite, gelatin, silica gel, isinglass, or

other fining agents is used to clarify wine, mead, and beer. Added late in the brewing process,

chitosan improves flocculation, and removes yeast cells, fruit particles, and other detritus that cause

hazy wine. Chitosan combined with colloidal silica is becoming a popular fining agent for white wines,

because chitosan does not require acidic tannins (found primarily in red wines) to flocculate with.[28]

[edit]Industrial use

Scientists have recently developed a polyurethane coating that heals its own scratches when exposed

to sunlight, offering the promise of scratch-free cars and other products. The self-healing coating uses

chitosan incorporated into traditional polymer materials, such as those used in coatings on cars to

protect paint. When a scratch damages the chemical structure, the chitosan responds to ultraviolet

light by forming chemical chains that begin bonding with other materials in the substance, eventually

smoothing the scratch. The process can take less than an hour.[29]

Marek W. Urban, a scientist working on this project said that the polymer can only repair itself in the

same spot once, and would not work after repeated scratches.[30]

[edit]Biomedical use

Chitosan's properties allow it to rapidly clot blood, and has recently gained approval in the United

States and Europe for use in bandages and other hemostatic agents. Chitosan hemostatic products

have been shown in testing by the U.S. Marine Corps to quickly stop bleeding and result in 100%

survival of otherwise lethal arterial wounds in swine and to reduce blood loss.[31] Chitosan hemostatic

products reduce blood loss in comparison to gauze dressings and increase patient survival.

[32] Chitosan hemostatic products have been sold to the U.S. Army and are currently used by the UK

military. Both the US and UK have already used the bandages on the battlefields

of Iraq and Afghanistan.[33]Chitosan is hypoallergenic, and has natural anti-bacterial properties, further

supporting its use in field bandages.[34]

[edit]Claimed health benefits

Chitosan is frequently sold in tablet form at health stores as a "fat binder": It is supposed to have the

capability to interact with lipids (fat) from the digestive system and limit their absorption in the body.

Therefore, chitosan can be an effective complement to help lose weight during diet period or to

stabilise ones weight. In the 2007 Cochrane meta-analysis [35] which evaluated all available clinical

trials performed with chitosan on the subject of weight loss, it was concluded that body weight and all

parameters related to cholesterol changed in favor of chitosan compared to placebo. The mean

difference in body weight was −1.7 kg (range: −2.1 to −1.3) in favor of chitosan. This change in body

weight was statistically significant. There was no difference between chitosan and placebo concerning

side effects. The various qualities (in terms of duration, sample size, doses, subject characteristics,

type of diet, chitosan quality and characteristics, etc.) of the clinical trials performed to evaluate the

effect of chitosan on body weight might account for some of the disparities observed in clinical trial

results [36] and the subsequent critics regarding the real efficacy of chitosan. In an experimental model

of the stomach and duodenum tract, chitosan has shown to interact with oil, which inhibited duodenal

absorption and enhanced lipid excretion [37]. However, the mechanism of interaction between chitosan

and fat is not very well understood and has not been really proved clinically yet [38]. This is certainly the

reason why the FDA has issued in 2004 Warning Letters to 2 companies who made inappropriate

claims according to the regulator [39]. Although detractors claim that using chitosan may have the

deleterious effect of rendering ineffective certain minerals found in foodstuffs, several animal studies

contradicted this statement by showing no or little effect. In mice, dietary ingestion of chitosan did not

depress the level of iron, zinc or copper [40]. Moreover, there is no proof of any adverse events, in

particular regarding nutrient absorption, in humans.

[edit]Medical Research

Chitosan is currently the focus of much medical research, as it is a polyglucosamine (the second-most-

common dietary fiber, after cellulose).[41] Studies have shown that chitosan has the following

properties:

As a soluble dietary fiber, it

increases gastrointestinal lumen viscosity[1] and slows down the

emptying of the stomach.

It alters bile acid composition, increasing the excretion of sterols and

reducing the digestibility of ileal fats.[42][43][44] It is unclear how chitosan

does this, but the currently favored hypotheses involve the increase

of intestinal viscosity or bile acid-binding capacity.[45]

Chitosan is relatively insoluble in water, but can be dissolved by

dilute acids, which would make it a highly-viscuous dietary fiber.

[45]Such fibers might inhibit the uptake of dietary lipids by

increasing the thickness of the boundary layer of

the intestinal lumen, which has been observed in animal

experiments.[46]

Having very few acetyl groups, chitosan contains cationic groups.

[8] This may cause chitosan to have bile acid-binding capacity,

which causes mixed micelles to be entrapped or disintegrated in

the duodenum and ileum.[45] This would interrupt bile acid

circulation, causing reduced lipid absorption and increased sterol

excretion, which has also been observed in animal experiments.

[44][45][46]

ChitinFrom Wikipedia, the free encyclopedia

Structure of the chitin molecule, showing two of the N -acetylglucosamine  units that repeat to form long chains in β-

1,4 linkage.

Chitin (C8H13O5N)n (pronounced /ˈkaɪtɨn/) is a long-chain polymer of a N -acetylglucosamine , a

derivative of glucose, and is found in many places throughout the natural world. It is the main

component of the cell walls of fungi, the exoskeletons of arthropods such

as crustaceans (e.g.crabs, lobsters and shrimps) and insects, the radulas of mollusks and the beaks

of cephalopods, including squid and octopuses. Chitin may be compared to the

polysaccharide cellulose and to the protein keratin. Although keratin is a protein, and not

a carbohydrate like chitin, keratin and chitin have similar structural functions. Chitin has

also proven useful for several medical and industrial purposes.

Contents

 [hide]

1   Etymology

2   Chemistry, physical properties and biological function

3   Fossil record

4   Uses

o 4.1   Agriculture

o 4.2   Industrial

o 4.3   Medicine

5   See also

6   References

7   External links

[edit]Etymology

The English word "chitin" comes from the French word "chitine", which first appeared in 1836. These

words were derived from the Greek word "chitōn", meaning mollusk. That is either influenced by, or

related to the Greek word khitōn, meaning "tunic" or "frock", the Central Semiticword "*kittan",

the Akkadian words "kitû" or "kita’um", meaning flax or linen, and the Sumerian word "gada" or "gida".[1]

A similar word, "chiton", refers to a marine animal with a protective shell (also known as a "sea

cradle").

[edit]Chemistry, physical properties and biological function

Chitin is a modified polysaccharide which contains nitrogen; it is synthesized from units of N -

acetylglucosamine (more precisely, 2-(acetylamino)-2-deoxy-D-glucose). These units form covalent β-

1,4 linkages (similar to the linkages between glucose units forming cellulose). Chitin may therefore be

described as cellulose with one hydroxyl group on each monomer substituted with

an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving

the chitin-polymer matrix increased strength.

A cicada sheds its chitinous exoskeleton.

In its unmodified form, chitin is translucent, pliable, resilient and quite tough. In arthropods, however, it

is often modified, becoming embedded in a hardened proteinaceous matrix, which forms much of

the exoskeleton. In its pure form it is leathery, but when encrusted in calcium carbonate it becomes

much harder.[2] The difference between the unmodified and modified forms can be seen by comparing

the body wall of a caterpillar (unmodified) to a beetle (modified).

[edit]Fossil record

For more on the preservation potential of chitin and other biopolymers, see taphonomy.

Chitin first appeared in the exoskeletons of Cambrian arthropods, e.g. trilobites. The oldest preserved

chitin dates to the Oligocene, about 25 million years ago.[3]

[edit]Uses

[edit]Agriculture

Most recent studies point out that chitin is a good inducer for defense mechanisms in plants.[4] It was

recently tested as a fertilizer that can help plants develop healthy immune responses, and have a

much better yield and life expectancy.[5] The EPA regulates chitin for agricultural use within the USA.

[6] Chitosan is derived from chitin, which is used as a biocontrol elicitor in agriculture and horticulture.

[edit]Industrial

Chitin is used industrially in many processes. It is used as an additive to thicken and stabilize foods

and pharmaceuticals. It also acts as a binder in dyes, fabrics, and adhesives. Industrial separation

membranes and ion-exchange resins can be made from chitin. Processes tosize and

strengthen paper employ chitin.[citation needed]

[edit]Medicine

Chitin's properties as a flexible and strong material make it favorable as surgical thread.

Its biodegradibility means it wears away with time as the wound heals. Moreover, chitin has some

unusual properties that accelerate healing of wounds in humans.[7]

Occupations associated with high environmental chitin levels, such as shellfish processors, are prone

to high incidences of asthma. Recent studies have suggested that chitin may play a role in a possible

pathway in human allergic disease. Specifically, mice treated with chitin develop an allergic response,

characterized by a build-up of interleukin-4 expressing innate immune cells. In these treated mice,

additional treatment with a chitinase enzyme abolishes the response.[8]