Various Red Algae Kosher Agar Agar is derived from two species of red algae in the Rhydophyceae family, Gelidium and Gracilaria. The powdered form is an excellent gelling agent and thickener in a variety of foods including jams, jellies, pudding, icings, soups and even ice-cream. Agar is an excellent vegetarian alternative to gelatin. Used in microbiology as a growing media for yeast, mold and bacteria. Used to make casts in prosthetic dentistry. Agar is processed by hot-water extractions from the cleaned and bleached seaweed, followed by freezing to allow for the removal of soluble salts and finally, filtration. The resulting extract is then dried and milled to the desired particle size.