Source & Processing
Agar or Agar-Agar is a dried hydrophilic, colloidal polygalactoside extracted from Gelidium Cartilagineum, Gracilaria Confervoides and related red algae. These seaweeds grow in the ocean on the rocks from tide line out to depths of 120 feet in many parts of the world. The weeds are harvested by waders along the shore at low tide, raked by fisherman from small boats, and picked by skin divers or divers in suits.
This old “natural method” of extracting the Agar from the seaweed has been replaced by commercial methods, which are still based on the fundamental principles of hot water extractions, cooling to form a gel, freezing, thawing, and drying. The latest mechanical, scientific processing utilizes chemical treatment of the weed, pressure extraction, artificial freezing and drying, chemical bleaching and many more advanced methods.
Agar is used primarily for its gelling properties, the wide difference between gelation temperature and gel-melting temperature, and the heat resistance of its gels. It is also used for its emulsifying and stabilizing properties. It is practically indigestible.
Agar is used as a stabilizer in cookies, cream shells, piping gels, pie fillings, shiffon pies, icings, and meringues as an anti-tackiness ingredient. Agar, at a sue level of 0.2–0.5% in icings prevents the sugar from adhering to the wrapper. The drying time of the icing can be regulated by varying the amount of agar used. The use of 0.5-1.0% Agar, based on sugar, increases the viscosity of doughnut glaze stabilizers, increases its adherence to the doughnut, and provides quicker setting and flexibility with reduced chipping and and cracking. Agar has been used with success as an anti-staling agent in breads and cakes. Agar is useful in low-calorie, non-starch breads, biscuits, and desserts as a non-nutritive bulking agent.
Agar is used at 0.5–2.0% of the broth weight as a thickening and gelling agent by poultry, fish, and meat canners to eliminate transit damage to fragile tissues. Agar, added to Guar Gum, gives better stabilization of water and fat in pet foods as well as meat pies. Canned baby foods, jams and marmalades also use Agar.
Agar has been used as a laxative since it forms a smooth, nonirritating bulk. In addition, it is not habit forming. It is also used as a suspending agent for barium sulfate in radiology, in slow release capsules, suppositories, surgical lubricants, emulsions, as a carrier of topical medicaments. In prosthetic dentistry, Agar is used to make accurate negative casts of teeth, sockets, and entire edentulous gums in order to form accurate artifacts.
Agar, low in metabolizable or inhibitory substances, debris and thermoduric spores, with a gelation temperature of 35–40° Celsius, which is readily soluble and has good gel firmness, clarity, and solubility is ideal for the propagation and pure culture study of yeast, molds and bacteria. No completely satisfactory substitutes are known, and Agar is commonly used at 1–2% for this purpose. At 0.007–0.08%, Agar prevents the entry of oxygen into liquid media, making cultivation of anaerobes feasible in air-exposed broths.