Introduction to Agar

Gelidium seaweed – a source of agar

Agar, also known as agar-agar, is a cell wall polysaccharide that is extracted from certain red seaweeds and used as a gelling agent. The gelling fraction is essentially a sulphated galactan consisting of alternating units of ⍺-(1-4)-L-galactose and β-(1-3)-D-galactopyranose. Agar has been widely used in the East for several hundred years, certainly since the seventeenth century when it is claimed to have been discovered in Japan by Tarazaemon Minoya (1658).

The industry as we know it today was founded on extraction from Gelidium seaweeds that were essentially wild harvested but with demand far out stripping natural supply, it now relies heavily on cultivated seaweeds, primarily species of Gracilaria. Other species used for the extraction of agar include Gelidiella, Pterocladia & Ahnfeltia. These different species yield agars with different properties.

Agar is eaten extensively in Asia as a flavoured jelly where the brittle texture is appreciated. However, for western consumers brought up on the jelly texture of gelatin, this is less acceptable. Agar is useful in the food industry as a gelling and thickening agent with particularly good functionality in acidic dairy products where it is used as a stabiliser. Another key property of agar is the large hysteresis 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. Click here to read and download the full article.

Read More

Read more on Agar