Agar

Agar

IUPAC Name:	{{{IUPACName}}}
Other Names:	Agar-agar
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Properties
Chemical formula	CHNO
Appearance	White to pale yellow powder
Density	1.0 g/cm3
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Solubility	Insoluble in cold water, soluble in boiling water
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Agar agar

Agar is a substance extracted from the cell walls of red algae. It is commonly used as a thickener, stabilizer, and gelling agent in a variety of food and industrial applications. Agar is also used in microbiology as a culture medium for growing bacteria and other microorganisms.

History

Agar was discovered in the mid-17th century by Japanese scientist Mino Tarōzaemon, who noticed that it was being used to thicken soups in Japan. He later extracted it from the cell walls of a red seaweed and identified it as a polysaccharide. Agar quickly became popular in Japan as a culinary ingredient, and was introduced to Europe in the 1850s.

Production

Agar is extracted from several species of red algae, including Gelidium, Gracilaria, and Pterocladia. The seaweed is washed and dried, and then boiled in water to release the agar. The agar is then filtered, purified, and dried into a powder or flakes.

Uses

Food

Agar is commonly used as a gelling agent in a variety of foods, including desserts, jellies, and confectionery. It can also be used as a thickener in soups, sauces, and gravies. Agar has several advantages over other gelling agents, including its ability to form a stable gel at a wide range of temperatures, and its lack of flavor, color, and odor.

Microbiology

Agar is also commonly used in microbiology as a culture medium for growing bacteria and other microorganisms. It provides a solid surface for the microorganisms to grow on, and can also be used to select for specific types of bacteria or to test the effectiveness of antimicrobial agents.

Industrial

Agar is also used in a variety of industrial applications, including textile printing, paper manufacturing, and as a thickener and stabilizer in pharmaceuticals and cosmetics.

Types

There are several different types of agar, each with its own unique properties and applications. Some of the most common types include:

Nutrient agar: Used for general bacterial culture. Blood agar: Used for culturing bacteria that require blood to grow. Chocolate agar: Used for culturing fastidious bacteria that require extra nutrients. MacConkey agar: Used for differentiating between lactose-fermenting and non-fermenting bacteria.

Safety

Agar is generally considered safe for human consumption, and is classified as a food additive by regulatory agencies around the world. However, some individuals may be allergic to agar, and excessive consumption can cause digestive issues.

In popular culture

Agar has appeared in various popular culture references. For instance, in the anime and manga series "Cells at Work!", agar is frequently used as a medium for growing cells and bacteria. In the science fiction film "The Andromeda Strain," agar is used as a culture medium to study an extraterrestrial microbe. Agar has also been featured in several cooking and baking shows, where it is used to make various desserts and confections.

See also

Gelidium Gracilaria Pterocladia

External links

Agar in Microbiology FDA information on agar as a food additive

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