Used in cooking, agar-agar is a gelatin made from what?
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Agar Gelatin
Agar (pronounced,, "") or agar-agar (,, "") is a jelly-like substance, obtained from algae.  It was discovered in the late 1650s or early 1660s by Mino Tarōzaemon in Japan, where it is called kanten.

Agar is derived from the polysaccharide agarose, which forms the supporting structure in the cell walls of certain species of algae, and which is released on boiling. These algae are known as agarophytes and belong to the Rhodophyta (red algae) phylum.  Agar is actually the resulting mixture of two components: the linear polysaccharide agarose, and a heterogeneous mixture of smaller molecules called agaropectin. 

Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture media for microbiological work. Agar can be used as a laxative, an appetite suppressant, a vegetarian substitute for gelatin, a thickener for soups, in fruit preserves, ice cream, and other desserts, as a clarifying agent in brewing, and for sizing paper and fabrics. 

The gelling agent in agar is an unbranched polysaccharide obtained from the cell walls of some species of red algae, primarily from the genera Gelidium and Gracilaria. For commercial purposes, it is derived primarily from Gelidium amansii. In chemical terms, agar is a polymer made up of subunits of the sugar galactose.

Background 

Agar was discovered around 1658 in Japan (where it is called kanten, coined from the phrase kan-zarashi tokoroten or “cold-exposed agar”) by Mino Tarōzaemon, an innkeeper who was said to have discarded some surplus seaweed soup and noticed that it gelled later after a winter night's freezing. 

Agar was first used in microbiology in 1882  by the German microbiologist Walther Hesse, an assistant working in Robert Koch's laboratory, on the suggestion of his wife Angelina Fannie Eilshemius Hesse. He discovered that it was more useful as a solidifying agent than gelatin, due to its better solidifying temperature.   

Agar was first subjected to chemical analysis in 1859 by the French chemist Anselme Payen, who had obtained agar from the marine algae Gelidium corneum. 

Agar consists of a mixture of agarose and agaropectin. Agarose, the predominant component of agar, 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. Agaropectin is a heterogeneous mixture of smaller molecules that occur in lesser amounts, and is made up of alternating units of D-galactose and L-galactose heavily modified with acidic side-groups, such as sulfate and pyruvate.   

Agar exhibits hysteresis, melting at 85 °C (358 K, 185 °F) and solidifying from 32–40 °C (305–313 K, 90–104 °F). This property lends a suitable balance between easy melting and good gel stability at relatively high temperatures. Since many scientific applications require incubation at temperatures close to human body temperature (37 °C), agar is more appropriate than other solidifying agents that melt at this temperature, such as gelatin.

The word "agar" comes from agar-agar, the Malay/Indonesian name for red algae (Gigartina, Gracilaria) from which the jelly is produced.,  and is also an ingredient in traditional Malay and Japanese desserts. It is also known as Kanten, Japanese isinglass, Ceylon moss or Jaffna moss.  Gracilaria lichenoides is specifically referred to as agal-agal or Ceylon agar. 

Uses

Microbiology 

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. Other ingredients are added to the agar to meet the nutritional needs of the microbes. Many specific formulations are available, because some microbes prefer certain environmental conditions over others.  Agar is often dispensed using a sterile media dispenser.

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 

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 in general are used. A 1.0% agar/0.44% MS+vitamin dH2O 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 influence phytohormone sensitivity of the plant cell culture. 

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. Sweetener, flavouring, colouring, fruit or vegetables are then added and the liquid is poured into molds to be served as desserts and vegetable aspics, or incorporated with other desserts, such as a jelly layer in 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 (the Japanese word for agar-agar) diet. Once ingested, kanten triples in size and absorbs water. This results in the consumers feeling fuller. This diet has recently received some press coverage in the United States as well. The diet has shown promise in obesity studies. 

One use of agar in Japanese cuisine (Wagashi) 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 mizu yōkan, another popular Japanese food.

In Philippine cuisine, it is used to make the jelly bars in the various gulaman refreshments or desserts such as sago gulaman, buko pandan, agar flan, halo-halo, and the black and red gulaman used in various fruit salads.

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. 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 )) is made from agar.

In Russia, it is used in addition or as a replacement to pectin in jams and marmalades, 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 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. 

Other uses 

Agar is used:
* As an impression material in dentistry.
* To make salt bridges and gel plugs for use in electrochemistry.
* In formicariums as a transparent substitute for sand and a source of nutrition.
* As a natural ingredient to form modelling clay for young children to play with.
* As an allowed biofertilizer component in organic farming. 
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 system called Agar Plasticity, intended as a replacement for oil-based plastic packaging. Gelatin or gelatine (from  meaning "stiff", "frozen") is a translucent, colorless, brittle (when dry), flavorless food derived from collagen obtained from various animal raw materials. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar way are called "gelatinous". Gelatin is an irreversibly hydrolyzed form of collagen, wherein the hydrolysis results in the reduction of protein fibrils into smaller peptides, which will have broad molecular weight ranges associated with physical and chemical methods of denaturation, based on the process of hydrolysis.  It is found in most gummy candy, as well as other products such as marshmallows, gelatin desserts, and some ice creams, dips, and yogurts.   Gelatin for recipe use comes in the form of sheets, granules, or powder. Instant types can be added to the food as they are; others need to be soaked in water beforehand.

Composition and properties

Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs and fish. During hydrolysis, the natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily. Its chemical composition is, in many respects, closely similar to that of its parent collagen.  Photographic and pharmaceutical grades of gelatin are generally sourced from beef bones and pig skin.

Gelatin readily dissolves in hot water, and sets to a gel on cooling. When added directly to cold water, it does not dissolve well. Gelatin is also soluble in most polar solvents. Gelatin solutions show viscoelastic flow and streaming birefringence. Solubility is determined by the method of manufacture. Typically, gelatin can be dispersed in a relatively concentrated acid. Such dispersions are stable for 10–15 days with little or no chemical changes and are suitable for coating purposes or for extrusion into a precipitating bath.

The mechanical properties of gelatin gels are very sensitive to temperature variations, the previous thermal history of the gels, and time. These gels exist over only a small temperature range, the upper limit being the melting point of the gel, which depends on gelatin grade and concentration, but is typically less than 35 C and the lower limit the freezing point at which ice crystallizes. The upper melting point is below human body temperature, a factor which is important for mouthfeel of foods produced with gelatin. The viscosity of the gelatin/water mixture is greatest when the gelatin concentration is high and the mixture is kept cool at about 4 C. The gel strength is quantified using the Bloom test.

Production

The worldwide production amount of gelatin is about .  On a commercial scale, gelatin is made from by-products of the meat and leather industries. Recently, fish by-products have also been considered because they eliminate some of the religious obstacles surrounding gelatin consumption.
Gelatin is derived from pork skins, pork and cattle bones, or split cattle hides. The raw materials are prepared by different curing, acid, and alkali processes which are employed to extract the dried collagen hydrolysate. These processes may take several weeks, and differences in such processes have great effects on the properties of the final gelatin products.

Gelatin can also be prepared in the home. Boiling certain cartilaginous cuts of meat or bones results in gelatin being dissolved into the water. Depending on the concentration, the resulting stock (when cooled) will naturally form a jelly or gel. This process is used for aspic.

While many processes exist whereby collagen can be converted to gelatin, they all have several factors in common. The intermolecular and intramolecular bonds which stabilize insoluble collagen must be broken, and the hydrogen bonds which stabilize the collagen helix must also be broken. The manufacturing processes of gelatin consists of three main stages:

#Pretreatments to make the raw materials ready for the main extraction step and to remove impurities which may have negative effects on physio chemical properties of the final gelatin product
#The main extraction step, which is usually done with hot water or dilute acid solutions as a multistage extraction to hydrolyze collagen into gelatin
#The refining and recovering treatments including filtration, clarification, evaporation, sterilization, drying, rutting, grinding, and sifting to remove the water from the gelatin solution, to blend the gelatin extracted, and to obtain dried, blended and ground final product

Pretreatments

If the raw material used in the production of the gelatin is derived from bones, dilute acid solutions are used to remove calcium and other salts. Hot water or several solvents may be used to reduce the fat content, which should not exceed 1% before the main extraction step. If the raw material consists of hides and skin; size reduction, washing, removal of hair from hides, and degreasing are necessary to prepare the hides and skins for the main extraction step.

Collagen hydrolysis is performed by one of three different methods: acid-, alkali-, and enzymatic hydrolysis. Acid treatment is especially suitable for less fully crosslinked materials such as pig skin collagen and normally requires 10 to 48 hours. Alkali treatment is suitable for more complex collagen such as that found in bovine hides and requires more time, normally several weeks. The purpose of the alkali treatment is to destroy certain chemical crosslinks still present in collagen. Within the gelatin industry, the gelatin obtained from acid-treated raw material has been called type-A gelatin and the gelatin obtained from alkali-treated raw material is referred to as type-B gelatin. 

Enzymatic hydrolysis of collagen for gelatin extraction is relatively new. However, the treatment time is shorter than that required for alkali treatment, and results in almost complete conversion to the pure product. The physical properties of the final gelatin product are better.

Extraction

After preparation of the raw material, i.e., reducing cross-links between collagen components and removing some of the impurities such as fat and salts, partially purified collagen is converted into gelatin by extraction with either water or acid solutions at appropriate temperatures. All industrial processes are based on neutral or acid pH values because though alkali treatments speed up conversion, they also promote degradation processes. Acidic extraction conditions are extensively used in the industry, but the degree of acid varies with different processes. This extraction step is a multistage process, and the extraction temperature is usually increased in later extraction steps, which ensures  minimum thermal degradation of the extracted gelatin.

Recovery

This process includes several steps such as filtration, evaporation, drying, grinding, and sifting. These operations are concentration-dependent and also dependent on the particular gelatin used. Gelatin degradation should be avoided and minimized, so the lowest temperature possible is used for the recovery process. Most recoveries are rapid, with all of the processes being done in several stages to avoid extensive deterioration of the peptide structure. A deteriorated peptide structure would result in a low gel strength, which is not generally desired.

Uses

Culinary uses

Probably best known as a gelling agent in cooking, different types and grades of gelatin are used in a wide range of food and nonfood products:
Common examples of foods that contain gelatin are gelatin desserts, trifles, aspic, marshmallows, candy corn, and confections such as Peeps, gummy bears, fruit snacks, and jelly babies. Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as yogurt, cream cheese, and margarine; it is used, as well, in fat-reduced foods to simulate the mouthfeel of fat and to create volume. It is also used in the production of several types of Chinese soup dumplings, specifically Shanghainese soup dumplings, or xiaolongbao, as well as Shengjian mantou, a type of fried and steamed dumpling. The fillings of both are made by combining ground pork with gelatin cubes, and in the process of cooking, the gelatin melts, creating a soupy interior with a characteristic gelatinous stickiness.

Gelatin is used for the clarification of juices, such as apple juice, and of vinegar. Isinglass, from the swim bladders of fish, is still used as a fining agent for wine and beer.  Beside hartshorn jelly, from deer antlers (hence the name "hartshorn"), isinglass was one of the oldest sources of gelatin.

Technical uses

* Certain professional and theatrical lighting equipment use color gels to change the beam color. These were historically made with gelatin, hence the term color gel.
* Gelatin typically constitutes the shells of pharmaceutical capsules to make them easier to swallow. Hypromellose is a vegetarian-acceptable alternative to gelatin, but is more expensive to produce.
* Some animal glues such as hide glue are essentially unrefined gelatin.
* It is used to hold silver halide crystals in an emulsion in virtually all photographic films and photographic papers. Despite some efforts, no suitable substitutes with the stability and low cost of gelatin have been found.
* Used as a carrier, coating, or separating agent for other substances, for example, it makes β-carotene water-soluble, thus imparting a yellow color to any soft drinks containing beta-carotene.
* Gelatin is closely related to bone glue and is used as a binder in match heads and sandpaper.
* Cosmetics may contain a nongelling variant of gelatin under the name hydrolyzed collagen.
* Gelatin was first used as an external surface sizing for paper in 1337 and continued as a dominant sizing agent of all European papers through the mid-19th century.  In modern times, it is mostly found in watercolor paper, and occasionally in glossy printing papers, artistic papers, and playing cards, and it maintains the wrinkles in crêpe paper.

Other uses

* Blocks of ballistic gelatin simulate muscle tissue as a standardized medium for testing  ammunition.
* Gelatin is used by synchronized swimmers to hold their hair in place during their routines, as it will not dissolve in the cold water of the pool. It is frequently referred to as "knoxing", a reference to Knox brand gelatin. 
* When added to boiling water and cooled, unflavored gelatin can make a home-made hair styling gel that is cheaper than many commercial hair styling products, but by comparison has a shorter shelf life (about a week) when stored in this form (usually in a refrigerator). After being applied to scalp hair, it can be removed with rinsing and some shampoo.
* It is commonly used as a biological substrate to culture adherent cells.
* It may be used by those who are sensitive to tannins (which can irritate the stomach) in teas, soups or brews.
* It may be used as a medium with which to consume LSD. LSD in gelatin form is known as "windowpane" or "geltabs".
* Gelatin is used to make the shells of paintballs, similar to the way pharmaceutical capsules are produced.
* It is used as an ingredient in implantable medical devices, such as in some bone void fillers. 
* It is used in nail polish remover and makeup applications. The gelatin is often tinted in different colors to match a model's natural skin tone.
* Leaf or sheet gelatin is used directly in food-based model-making, for example to make translucent, edible, diamond-paned windows in gingerbread houses.
* Gelatin can be used as a binding agent in India ink.
* It may be used as a technique within the process of fine-art printmaking. The prints are made  by creating a block of gelatin and applying printing inks.  The gelatin is made using twice the normal amount of gelatin granules to the usual amount of water.  Once set – printmaking ink (usually water-based) is applied to its surface.  Other water-based media may also be applied.   Items such as dried grass,  leaves, and paper stencils are placed onto the inked surface.  Gelatin monotype is best done with the use of medium to lightweight paper.  This is  gently pressed onto the inked plate once the 'design' has been composed.

Dietary restrictions and gelatin substitutes

The consumption of gelatin from particular animals may be forbidden by religious or cultural rules. For example, Jewish kosher and Islamic halal customs require gelatin from sources other than pigs, such as cattle or fish and from animals slaughtered ritually.  Roma people are cautious of gelatin products that may have been made from horses, as their culture forbids the consumption of horses. Some companies specify the source of the gelatin used. Vegans and many vegetarians choose not to eat foods containing gelatin made from animals. Likewise, Hindu and Jain customs may require gelatin alternatives from sources other than animals, as many Hindus are vegetarian. Hindus who are not vegetarians often consume gelatin from all sources except cattle, which are considered sacred. However, since many people are not aware about gelatin's sources, they unknowingly consume it. Other people simply consider gelatin unpalatable due to the ingredients used in its production.

Partial, nonanimal alternatives to gelatin include the seaweed extracts agar and carrageenan, as well as pectin and konjac. Research into synthetic collagen is ongoing; as of 2011, partial success has been achieved in replicating collagen's structure using self-assembling peptides. 

Protein content

Although gelatin is 98–99% protein by dry weight, it has little other nutritional value varying  on the source of the raw material and processing technique.

Safety concerns

The U.S. Food and Drug Administration (FDA), with support from the TSE (transmissible spongiform encephalopathy) Advisory Committee, has since 1997 been monitoring the potential risk of transmitting animal diseases, especially bovine spongiform encephalopathy (BSE), commonly known as mad cow disease. The FDA study concluded:  "...steps such as heat, alkaline treatment, and filtration could be effective in reducing the level of contaminating TSE agents; however, scientific evidence is insufficient at this time to demonstrate that these treatments would effectively remove the BSE infectious agent if present in the source material." 

The Scientific Steering Committee (SSC) of the European Union in 2003 stated that the risk associated with bovine bone gelatin is very low or zero.  
In 2006, the European Food Safety Authority (EFSA) stated that the SSC opinion was confirmed, that the BSE risk of bone-derived gelatin was very small, and removed support for the 2003 request of excluding the skull and vertebrae of bovine origin older than 12 months from the material used in gelatin manufacturing. 

All reputable gelatin manufacturers today follow the Quality Management System according to ISO 9001. In this way, all process steps are documented. For pharmaceutical-grade gelatins, strict regulations from the FDA, the European CPMP's regulation and European Pharmacopoeia must be met. A detailed overview of the regulatory requirements for gelatin production can be found in the Gelatine Handbook, pp. 99–101. 

Health effects

In 2011, reviewing the clinical data that had been published to date, the European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies concluded that "a cause and effect relationship has not been established between the consumption of collagen hydrolysate and maintenance of joints". 

A 2012 review also found insufficient evidence to support its use for osteoarthritis.  However, in 2013, Health Canada approved a label for "hydrolyzed collagen" specifying that the label can say that it is useful to supplement dietary amino acid intake, and that it "helps to reduce joint pain associated with osteoarthritis."
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