CAS 9002-18-0: Agar

Agar-agar

Agar has a wide range of applications in life science related research.

Agar is the most suited solidifying agent for scientific applications that require incubation temperatures closer to human body temperature. Agar is used as a medium in bacteriology and plant biology, impression material in dentistry, biofertilizer in organic farming, and salt bridges in electrochemistry. It can be used to measure the motility and mobility of microorganism owing to the porous nature of the gel form of an agar or agarose medium. This Thermo Scientific Chemicals brand product was originally part of the Alfa Aesar product portfolio. Some documentation and label information may refer to the legacy brand. The original Alfa Aesar product / item code or SKU reference has not changed as a part of the brand transition to Thermo Scientific Chemicals.

Agar (micro agar)

Agar, plant cell culture tested

The major gel forming component in agar, agarose, consists of a linear chain of sequences of 1,3 linked β-D-galactopyranosyl units and 1,4 linkages to 3,6-anhydro-α-L-galactopyranosyl units. Gelation is done via the formation of double helices (Arnott, 1974). Agar's properties are similar to gelatin as it is primarily used as a plating gel for microbial cultures (Lahaye, 1991). However, agar is a good substitute for animal-based gelatin in vegetarian foods and is easy to use in food gels in a similar way to the carrageenans. Common food applications of agar include: puddings, custards, and soft candies. Agar improves the texture of processed cheese and frozen desserts, and is also added to baked goods to inhibit staling. A creative food application uses agar-based gel cubes that are infused with fruit extract or wine to make a vegetable-based aspic (Armisén, 2009). Agar contains two polysaccharides Agarobiose and Agaropectin. Both Gelidium latifolium and Gelidium amansii are sources of both Agar and Agarose. The images were kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’. Agaropectin Agaropectin is a sulphated non-gelling galactan comprising about 30% of Agar. Half ester sulphate is present in varying amounts plus D-glucuronic acid and small amounts of pyruvic acid. As with Agarose the main chain has alternating residues of D-galactose and L-galactose heavily modified with acidic side-groups which are usually sulfate, glucuronate, and pyruvate. Pyruvic acid is possibly attached in an acetal form to the D-galactose residues of the agarobiose skeleton. No formal structure of Agaropectin appears to have been published. Agarose Agarose is a linear gelling polysaccharide of (1-3) linked β-D-galactopyranose residues linked to 3,6-anhydro-α-L-galactopyranose via 1-4 bonds. Agar contains about 60% Agarose.

PTC Agar