Agar, more correctly known as agar-agar, has been used in the East for several hundred years and certainly since the seventeenth century. Agar is traditionally claimed to have been discovered by Tarazaemon Minoya in 1658 in Japan.
Agar is typically a strong gelling polysaccharide derived from red seaweeds and is characterised by its chemical repeat units of 3-6,anhydro L-Galactose. Agars also contain sulphate esters in low levels and some methoxy groups.
Agar is eaten extensively in Asia has a flavoured jelly where the brittle texture is appreciated. However for western tases, brought up on gelatin, this is less acceptable. Agar is useful in the food industry as a gelling and thickening agent with particularly good properties in acidic dairy products where it is used as a stabiliser. Another key property of agar is the large hystersis between the melting and setting temperatures which is unusual for a polysaccharide. One of the single biggest users of agar in the west is in the baking industry where the very high melting points of the agar gels make them particularly suitable to the baking process. Agar has good compatibility with sugar and can be used in very high sugar environments that would precipitate most other gums. Agar is often used to provide structure to high sugar systems such as doughnut icing.
This Introduction to Agar article has further information on agar structure, production and properties which can be accessed using the forward arrows in the Further Reading box below.