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Agar (pronounced , , "") or agar-agar (, , "") is a jelly-like substance, obtained from algae.〔ODE 2nd edition 2005〕 It was discovered in the late 1650s or early 1660s by Mino Tarōzaemon (美濃 太郎左衛門) 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 (agar-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〔Robert Koch (10 April 1882) ("Die Aetiologie der Tuberculose" ) (The etiology of tuberculosis), ''Berliner Klinische Wochenschrift'' (Berlin Clinical Weekly), 19 : 221-230. From page 225: ''"Die Tuberkelbacillen lassen sich auch noch auf anderen Nährsubstraten kultiviren, wenn letztere ähnliche Eigenschaften wie das erstarrte Blutserum besitzen. So wachsen sie beispielsweise auf einer mit Agar-Agar bereiteten, bei Blutwärme hart bleibenden Gallerte, welche einen Zusatz von Fleischinfus und Pepton erhalten hat."'' (The tubercule bacilli can also be cultivated on other media, if the latter have properties similar to those of congealed blood serum. Thus they grow, for example, on a gelatinous mass which was prepared with agar-agar, which remains solid at blood temperature, and which has received a supplement of meat broth and peptone.)〕 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.〔(【引用サイトリンク】title=Bacterial nutrition )〕 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''.〔Payen, Anselme (1859) ("Sur la gélose et le nids de salangane" ) (On agar and swiftlet nests), ''Comptes rendus'' …, 49 : 521-530, appended remarks 530-532.〕 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 ) at lsbu.ac.uk Water Structure and Science〕〔(【引用サイトリンク】title= Chapter 1 - Production, Properties and Uses of Agar )〕 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.〔(Agar-Agar ) at Agar-Agar.org〕 ''Gracilaria lichenoides'' is specifically referred to as agal-agal or Ceylon agar.〔(Agar-Agar ) at Botanical.com〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Agar」の詳細全文を読む スポンサード リンク
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