Editing Agar (section)

==Uses==

=== Culinary ===
[[File:Sago Gulaman.jpg|thumb|''[[Sago]] at [[gulaman]]'' in [[Filipino cuisine]] is made from agar (''[[gulaman]]''), pearl [[sago]], and sugar syrup flavored with [[Pandanus amaryllifolius|pandan]].|210x210px]]
Agar-agar is a natural vegetable [[gelatin]] counterpart.<ref name=":0">{{Cite book |last=Wings of Success |title=The Advantages of Being a Vegetarian: Selected Tips |pages=9–10}}</ref><ref>{{Cite book |last=Livlaid |first=Nele |title=Plant-Based Made Easy: The Complete Practical Guide to Transitioning to Healthy Whole Food Diet |publisher=Nutriplanet (Swing & Step OU) |year=2018 |isbn=9789949882465}}</ref> It is white and semi-[[translucent]] when sold in packages as washed and dried strips or in powdered form.<ref name=":0" /><ref name=":1">{{Cite book |last=Stobart |first=Tom |title=Cook's Encyclopaedia |publisher=Grub Street Publishing |year=2016 |isbn=9781910690833}}</ref> It can be used to make jellies,<ref>{{Cite book |last1=Zhang |first1=Louisa |title=Home Economics S2 Tb (nt) |last2=Seng |first2=Teo Kiok |last3=Hixson |first3=Sue |last4=Kwone |first4=Eileen |publisher=Longman |year=2022 |isbn=9789814079471 |location=Singapore |pages=145}}</ref> [[puddings]], and [[custard]]s.<ref>{{Cite book |last=Ash |first=Michael |title=Handbook fo Fillers, Extenders, and Diluents |publisher=Synapse Information Resources |year=2007 |isbn=9781890595968 |pages=233}}</ref> When making jelly, it is boiled in water until the solids dissolve. Sweetener, flavoring, coloring, fruits and or vegetables are then added, and the liquid is poured into [[molding (process)|molds]] to be served as desserts and vegetable [[aspic]]s or incorporated with other desserts such as a layer of jelly in a [[cake]].<ref name=":1" />

Agar-agar is approximately 80% [[dietary fiber]], so it can serve as an intestinal regulator.<ref>{{Cite journal |last=Marden |first=Orison Swett |date=1921 |title=Constipation is a Crime |journal=The New Success: Marden's Magazine |publisher=Lowrey-Marden |volume=5 |pages=113}}</ref> Its bulking quality has been behind [[fad diet]]s in Asia, for example the ''kanten'' (the Japanese word for agar-agar<ref name="oxford" />) diet. Once ingested, ''kanten'' triples in size and absorbs water. This results in the consumers feeling fuller.

==== Asian culinary ====
One use of agar in [[Japanese cuisine]] is in ''[[anmitsu]]'', a dessert made of small cubes of agar jelly and served in a bowl with various fruits or other ingredients.{{citation needed|date=April 2024}} It is also the main ingredient in ''mizu yōkan'', another popular Japanese food.{{citation needed|date=April 2024}} In [[Philippine cuisine]], it is used to make the jelly bars in the various [[gulaman]] refreshments like ''[[sago't gulaman]]'', ''[[samalamig]]'', or desserts such as ''[[buko pandan]]'', ''agar flan'', ''[[halo-halo]]'', ''fruit cocktail jelly'', and the black and red ''gulaman'' used in various fruit salads.{{citation needed|date=April 2024}} In [[Vietnamese cuisine]], jellies made of flavored layers of agar-agar, called ''thạch'', are a popular dessert, and are often made in ornate molds for special occasions.{{citation needed|date=April 2024}} In [[Indian cuisine]], agar is used for making desserts.{{citation needed|date=April 2024}} In [[Burmese cuisine]], a sweet jelly known as ''kyauk kyaw'' is made from agar.{{citation needed|date=April 2024}} Agar jelly is widely used in Taiwanese [[bubble tea]].{{citation needed|date=April 2024}}

==== Other culinary ====
[[File:00114jfCuisine of Bulacan Food Cakes Delicaciesfvf 30.jpg|thumb|''[[Crema de fruta]]'', a traditional [[Filipino cuisine|Filipino]] fruitcake, is made with an agar layer on top to keep the fruit components in place.]]
It can be used as addition to (or as a replacement for) [[pectin]] in jelly, jam, or marmalade, as a substitute to gelatin for its superior gelling properties, and as a strengthening ingredient in souffles and custards. Another use of agar-agar is in a [[Russian cuisine|Russian]] dish ''ptich'ye moloko'' ([[bird's milk]]), a rich jellified custard (or soft [[meringue]]) used as a cake filling or chocolate-glazed as individual sweets.

Agar-agar may also be used as the gelling agent in gel clarification, a culinary technique used to clarify stocks, sauces, and other liquids. [[Mexico]] has traditional candies made out of Agar gelatin, most of them in colorful, half-circle shapes that resemble a [[melon]] or [[watermelon]] fruit slice, and commonly covered with sugar. They are known in Spanish as ''Dulce de Agar'' (Agar sweets)

Agar-agar is an allowed nonorganic/nonsynthetic additive used as a thickener, gelling agent, texturizer, moisturizer, emulsifier, flavor enhancer, and absorbent in certified organic foods.<ref>[http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5096516 Agar-agar Review Sheet] {{Webarchive|url=https://web.archive.org/web/20150620112844/http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5096516 |date=2015-06-20 }}, USDA Organic Materials Review, April 1995.</ref>

=== Microbiology ===
==== Agar plate ====
{{Main|Agar plate}}
[[Image:Agar Plate.jpg|right|thumb|{{cvt|100|mm|adj=on}} diameter [[Petri dish]]es containing agar gel for bacterial culture]]

An agar plate or [[Petri dish]] is used to provide a [[growth medium]] using a mix of agar and other nutrients in which microorganisms, including [[bacteria]] and [[fungi]], can be cultured and observed under the microscope. Agar is indigestible for many organisms so that microbial growth does not affect the gel used and it remains stable. 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. Nutrients are typically added to meet the nutritional needs of the [[microbe]]s organism, the formulations of which may be "undefined" where the precise composition is unknown, or "defined" where the exact chemical composition is known. Agar is often dispensed using a sterile [[media dispenser]].

Different algae produce various types of agar. Each agar has unique properties that suit different purposes. Because of the agarose component, the agar solidifies. When heated, agarose has the potential to melt and then solidify. Because of this property, they are referred to as "physical gels". In contrast, [[polyacrylamide]] polymerization is an irreversible process, and the resulting products are known as chemical gels.

There are a variety of different types of agar that support the growth of different microorganisms. A nutrient agar may be permissive, allowing for the cultivation of any non-fastidious microorganisms; a commonly-used nutrient agar for bacteria is the Luria Bertani (LB) agar which contains [[lysogeny broth]], a nutrient-rich medium used for bacterial growth.<ref>{{Cite journal |date=2009-03-01 |title=LB agar |url=http://cshprotocols.cshlp.org/content/2009/3/pdb.rec11683 |journal=Cold Spring Harbor Protocols |language=en |volume=2009 |issue=3 |pages=pdb.rec11683 |doi=10.1101/pdb.rec11683 |issn=1940-3402}}</ref> Additionally, 2216 Marine Broth (MB) agar, with high salt content, is optimized for growing heterotrophic marine bacteria like those of the Vibrio genus, while Terrific Broth (TB) agar is used to non-selectively culture high yields of the bacterium ''E. coli''. More generally, enriched media is an agar variety that is infused with the necessary nutrients required by fastidious organisms to grow. Despite the large diversity of agar mediums, yeast extract is a common ingredient across all varieties as it is a macronutrient that provides a nitrogen source for all bacterial cell types. 
[[File:Lactose fementing (LF), and non-lactose fermenting (NLF) colonies on MacConkey agar.jpg|thumb]]
Other fastidious organisms may require the addition of different biological fluids such as horse or sheep blood, serum, egg yolk, and so on.<ref>{{Citation |last1=Clark |first1=David P. |title=Chapter 7 – Cloning Genes for Synthetic Biology |date=2019-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780128132883000070 |work=Molecular Biology (Third Edition) |pages=199–239 |editor-last=Clark |editor-first=David P. |publisher=Academic Cell |language=en |doi=10.1016/b978-0-12-813288-3.00007-0 |isbn=978-0-12-813288-3 |access-date=2022-12-12 |last2=Pazdernik |first2=Nanette J. |last3=McGehee |first3=Michelle R. |s2cid=91889487 |editor2-last=Pazdernik |editor2-first=Nanette J. |editor3-last=McGehee |editor3-first=Michelle R.}}</ref> Agar plates can also be selective, and can be used to promote the growth of bacteria of interest while inhibiting others. A variety of chemicals may be added to create an environment favourable for specific types of bacteria or bacteria with certain properties, but not conducive for growth of others. For example, antibiotics may be added in cloning experiments whereby bacteria with antibiotic-resistant plasmid are selected.<ref>{{cite web |url=https://asm.org/Articles/2020/September/Why-Differential-Selective-Media-Are-Invaluable-To  |title=Why Differential & Selective Media Remain Invaluable Tools|date=September 25, 2020 |work=American Society for Microbiology}}</ref> In addition to antibiotic treated agar, other selective and indicator agar plates include TCBS agar and MacConkey agar. Thiosulfate citrate bile salts sucrose (TCBS) agar is used to differentiate Vibrio species based on their sucrose metabolism, since only some will metabolize the sucrose in the plate and change its pH. Indicator dyes included in the gel will display a visual change of the pH by changing the gel color from green to yellow. MacConkey agar contains bile salts and crystal violet to selectively grow gram-negative bacteria and differentiate between species using pH-indicator dyes that demonstrate lactose metabolism properties.
[[File:Microorganisms-11-01566-g008.webp|thumb]]

==== Motility assays ====
As a gel, an agar or 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 show growth only 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.

=== Plant biology ===
[[Image:Physcomitrella growing on agar plates.jpg|thumb|''[[Physcomitrella patens]]'' plants growing [[axenic]]ally [[in vitro]] on [[agar plate]]s. [[Petri dish]] has {{cvt|9|cm|adj=on}} diameter.]]

Research grade agar is used extensively in [[plant]] biology as it is optionally supplemented with a nutrient and/or vitamin mixture that allows for seedling germination in Petri dishes under sterile conditions (given that the seeds are sterilized as well). Nutrient and/or vitamin supplementation for ''[[Arabidopsis thaliana]]'' is standard across most experimental conditions. [[Murashige and Skoog medium|Murashige & Skoog]] (MS) nutrient mix and Gamborg's B5 vitamin mix in general are used. A 1.0% agar/0.44% MS+vitamin dH<sub>2</sub>O solution is suitable for growth media between normal growth temps.

When using agar, within any growth medium, it is important to know that the solidification of the agar is pH-dependent. The optimal range for solidification is between 5.4 and 5.7.<ref>{{cite book|last1=Kim|first1=Se-Kwon|title=Handbook of marine macroalgae : biotechnology and applied phycology|date=2011|publisher=John Wiley & Sons Inc.|location=Hoboken, NJ|isbn=9780470979181|edition=1st imp.}}</ref> Usually, the application of potassium hydroxide 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&nbsp;– agar or [[Gellan gum|Gelrite]] – does influence [[phytohormone]] sensitivity of the plant [[cell culture]].<ref name="Birgit Hadeler">
{{cite journal|title=Gelrite and agar differently influence cytokinin-sensitivity of a moss |journal=Journal of Plant Physiology |volume=146 |issue=3 |pages=369–371|author1 = Birgit Hadeler|author2 = Sirkka Scholz|author3=Ralf Reski |author-link3=Ralf Reski |doi=10.1016/s0176-1617(11)82071-7|year=1995 |bibcode=1995JPPhy.146..369H }}</ref>

=== Other uses ===
Agar is used:
* As an [[Dental impression|impression material]] in [[dentistry]].
* As a medium to precisely orient the tissue specimen and secure it by '''agar pre-embedding''' (especially useful for small endoscopy biopsy specimens) for [[histopathology]] processing<ref>{{cite journal|title = Improvised double-embedding technique of minute biopsies: A mega boon to histopathology laboratory |journal = Indian Journal of Pathology and Microbiology |url = https://www.researchgate.net/publication/272189364 |date = February 2015|volume = 58|issue =1|pages =12–6|doi =  10.4103/0377-4929.151156 |first1= Lokenddra |last1=Yadav|first2= Sarega |last2=Thomas|first3=Usha|last3= Kini|pmid = 25673584 |doi-access = free}}</ref>
* To make [[salt bridge]]s and gel plugs for use in [[electrochemistry]].
* In [[formicarium]]s as a transparent substitute for sand and a source of nutrition.
* As a natural ingredient in forming [[modeling clay]] for young children to play with.
* As an allowed biofertilizer component in organic farming.<ref>[https://books.google.com/books?id=icgrAQAAQBAJ&dq=agar+organic+farming&pg=PA184 Integrated Organic Farming Handbook], H. Panda, Asia Pacific Business Press Inc., Oct 4, 2013</ref>
* As a substrate for [[Precipitin#Precipitin reaction|precipitin reactions]] in [[immunology]].
* At different times as a substitute for [[gelatin]] in [[photographic emulsion]]s, [[arrowroot]] in preparing silver paper and as a substitute for [[Animal glue|fish glue]] in resist etching.<ref>{{Cite journal|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870000744.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870000744.pdf |archive-date=2022-10-09 |url-status=live|title=Black-and-White Photographic Chemistry|last=Walker|first=Ernie|date=June 1986|website=NASA Technical Reports Server}}</ref>
* As an MRI elastic gel phantom to mimic tissue mechanical properties in [[Magnetic Resonance Elastography]]<ref>{{cite journal |last1=McIlvain |first1=Grace |last2=Ganji |first2=Elahe |last3=Cooper |first3=Catherine |last4=Killian |first4=Megan L. |last5=Ogunnaike |first5=Babatunde A. |last6=Johnson |first6=Curtis L. |title=Reliable preparation of agarose phantoms for use in quantitative magnetic resonance elastography |journal=Journal of the Mechanical Behavior of Biomedical Materials |date=September 2019 |volume=97 |pages=65–73 |doi=10.1016/j.jmbbm.2019.05.001|pmid=31100487 |pmc=6699912 }}</ref>
* In the Arts, for example in "[[microbial art]]" in which agar acts as canvas, and microbes as a form of paint
Gelidium agar is used primarily for bacteriological plates. Gracilaria agar is used mainly in food applications.

In 2016, AMAM, a Japanese company, developed a prototype for Agar-based commercial [[Packaging and labeling|packaging]] system called Agar Plasticity, intended as a replacement for oil-based plastic packaging.<ref>{{Cite web|url=https://www.good.is/articles/agar-plasticity-amam-araki-maetani-muraoka-packaging|title=New Seaweed-Based Material Could Replace Plastic Packaging|website=Good Magazine|access-date=2016-04-03|date=2016-03-09}}</ref><ref>{{Cite web|url=http://www.fastcompany.com/3055784/design-award/design-looks-ahead|title=Design Looks Ahead|website=Fast Company|date=26 January 2016|language=en-US|access-date=2016-04-03}}</ref>