64 MARINE PRODUCTS OF COMMERCE 



other red algae, is insoluble in cold water but soluble in hot water, a one per cent 

 solution of which forms a firm gel. 



Since gel strength is the most important property of agar, the definition may 

 be improved by designating a "firm gel" as one in which a freshly cut surface will 

 support at least 50 gm of weight when added at the rate of 0.5 gm per second 

 through a plunger having a circular area of one square centimeter. Gels from 



Fig. 5-9. Gelidium cartilagineum from which agar is made in 

 California and Mexico. 



Irish moss, Gigartina, Agardhiella, Gloiopeltis, Phyllophora, and some species of 

 Gelidium and Gracilaria, which do not meet this requirement, may be referred 

 to as agaroids. 



Originally, the Malayan term "agar-agar" was used to refer to the seaweed 

 Eucheiinia muricatum, especially in dried form. Eucheiima yields an agaroid. 

 Since Irish moss gel and other agaroids have also been called agar, it is advisable 

 to determine an author's meaning of the term. It is, however, becoming more 

 precise in its use, conforming to the above definition. 



The Japanese Agar Industry. Raw material for the agar industry in Japan is 

 obtained from the entire coastline of the main island of Honshu. Surga Bay, in 

 the center of the south coast, is the area of greatest yield. Of the thirty or more 

 species of seaweeds utilized, Gelidium amansii is by far the most important. 

 Other widely used species include Gelidium pacificum, Gelidium, japonicuvfi, 

 Acanthopeltis japonica, Ceramium hypnaeoides, Gracilaria confervoides, Gelidium. 



