Agar-agar is a non-nitrogenous carbohydrate consisting of two polysaccharides namely agarose and agropectin. It is obtained from several red algae eg, Grecilaria, Gelidium, Geigartina etc. The alga Laminaria called kombu in Japan is rich in carbohydrate and iodine. Sargassum is used as food due to high nutritive value.