AGAR AND RELATED PIIYCOCOLLOIDS 71 



Carolina waters. In 1949 the factory had a capacity of 1 ton of dry seaweed per 

 day (350 to 400 pounds of agar). 



Seaweeds Utilized. In Cahfornia the principal agar-producing seaweed is 

 Gelidium cartilagineum (Fig. 5-9.) Two other species, G. nudijrons Gardner and 

 G. arborescens Gardner, are used to a limited extent; but, since they grow in 

 deeper water and produce a slightly inferior agar (with reference to gel strength), 

 they are unimportant. Material collected from these species is mixed indiscrimi- 

 nately with G. cartilagineum. Gracilaria confervoides was once used in California; 

 however, it has not been collected in recent years due to the relatively low gel 

 strength of its agar. The same species on the Atlantic Coast (as presently defined) 

 produces an agar of higher gel strength. 



Yield. California manufacturers ordinarily obtain a yield of 15 to 20 per cent 

 from the Gelidium cartilagineum of Pacific Coast waters. On the Atlantic Coast the 

 yield of all species so far utilized, Gracilaria confervoides, G. foliifera, and 

 Hypnea musciformis, has also ranged between 15 and 20 per cent on a commercial 

 scale. Yields above 20 per cent are rare. Laboratory yields of carefully prepared 

 raw material of these species range from 40 to 45 per cent or more. With 

 Gelidium only about 3 pounds of fresh material are required to make 1 pound of 

 dry material whereas with Gracilaria and Hypnea about 10 to 15 pounds are re- 

 quired. Thus the agar yield of Gelidium on a fresh basis is about 6 per cent while 

 the yield of fresh Gracilaria or Hypnea is only about 2 per cent. Gelidium cartila- 

 gineum grows firmly attached to rocks in turbulent water and is consequently dif- 

 ficult and costly to collect in quantity. Fresh Gelidium is worth about $80 per ton, 

 dry Gelidium about $350 per ton (Tseng, 1947). 



In North Carolina and Florida Gracilaria confervoides and G. foliifera ( G. multi- 

 partita J. Agardh; G. lacinulata [Vahl] Howe) constitute the principal raw mate- 

 rial. At first G. confervoides was the only plant in North Carolina of which use was 

 made, but in recent years G. foliifera has become of increasing importance. 

 Although G. confervoides occurs in Florida, G. foliifera, collected from the Indian 

 River, is more abundant. Agar from these two species is similar, but not identical. 

 In general G. confervoides agar is of slightly greater gel strength and exhibits a 

 lower viscosity as a melted solution. The gel strength of agar from G. foliifera from 

 North Carolina is slightly greater than that of agar from the same species from 

 Florida. Comparisons of G. foliifera agar from Florida, North Carolina, and New 

 Jersey indicate that the gel strength is inversely proportional to the water tempera- 

 ture. The correlation is supported by observations of gel strength of G. foliifera agar 

 from seaweed collected at different times of the year. 



The quantity of seaweed collected during the first 4 years of the agar industry 

 in North Carolina is given in Table 17. The figures are not indicative of quantities 

 available during 1943 and 1944 as intensive collecting was not undertaken until 



Table 17. Approximate Total Dry Weight in Pounds of Each Species of 



Seaweed Collected in North Carolina, 1943-1946. The Price was 



10 Cents Per Pound. 



