Agar

Agar (pronounced /ˈeɪɡɑːr/, sometimes /ˈɑːɡər/) or agar-agar is a jelly-like substance, obtained from red algae. Agar (pronounced /ˈeɪɡɑːr/, sometimes /ˈɑːɡər/) or agar-agar is a jelly-like substance, obtained from red algae. Agar is a mixture of two components: the linear polysaccharide agarose, and a heterogeneous mixture of smaller molecules called agaropectin. It forms the supporting structure in the cell walls of certain species of algae, and is released on boiling. These algae are known as agarophytes, and belong to the Rhodophyta (red algae) phylum. Agar has been 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 tengusa (Gelidiaceae) and ogonori (Gracilaria). For commercial purposes, it is derived primarily from ogonori. In chemical terms, agar is a polymer made up of subunits of the sugar galactose. Agar may have been discovered in Japan in 1658 by Mino Tarōzaemon (美濃 太郎左衛門), an innkeeper in current Fushimi-ku, Kyoto who, according to legend, was said to have discarded surplus seaweed soup and noticed that it gelled later after a winter night's freezing. Over the following centuries, agar became a common gelling agent in several Southeast Asian cuisines. 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. Beginning in the late 19th century, agar began to be used heavily as a solid medium for growing various microbes. Agar was first described for use in microbiology in 1882 by the German microbiologist Walther Hesse, an assistant working in Robert Koch's laboratory, on the suggestion of his wife Fannie Hesse. Agar quickly supplanted gelatin as the base of microbiological media, due to its higher melting temperature, allowing microbes to be grown at higher temperatures without the media liquefying. With its newfound use in microbiology, agar production quickly increased. This production centered on Japan, which produced most of the world's agar until World War II. However, with the outbreak of World War II, many nations were forced to establish domestic agar industries in order to continue microbiological research. Around the time of World War II, approximately 2,500 tons of agar were produced annually. By the mid-1970s, production worldwide had increased dramatically to approximately 10,000 tons each year. Since then, production of agar has fluctuated due to unstable and sometimes over-utilized seaweed populations. The word 'agar' comes from agar-agar, the Malay name for red algae (Gigartina, Gracilaria) from which the jelly is produced. It is also known as Kanten (Japanese: 寒天) (from the phrase kan-zarashi tokoroten (寒晒心太) or “cold-exposed agar”), Japanese isinglass, Ceylon moss or Jaffna moss. Gracilaria lichenoides is specifically referred to as agal-agal or Ceylon agar.