AGAR AND RELATED PHYCOCOLLOIDS 63 



emulsions and tablets), oil emulsions, insect sprays, and water-base inks, sizing 

 cloth and paper, and creaming rubber latex. 



In addition to the prepared extractives the seaweed itself is still offered in 

 pulverized form for use as a clarifying agent in breweries. Carrageenin has the 

 property of reacting with proteins in a manner that hastens coagulation and causes 

 precipitation. This settling gelatinous mass also carries with it other particulate 

 matter. It is added to hot beer wort (5 to 7 pounds per 500-barrel kettle) and a 

 general precipitation soon follows. A second protein coagulation and precipita- 

 tion occurs when the liquid has cooled to about 60° F (15.6° C), which brewers 

 call the "cold break." Removal of proteins previous to fermentation produces a 

 beer of superior flavor. 



In applying an Irish moss extractive it should be remembered that, for many 

 purposes, it is important to use a product which is easily soluble in water, has 

 proper relative acidity (pH), and contains the proper amount and kind of in- 

 organic salts to make it suitable for the purpose intended. 



New uses for Irish moss and other phycocoUoids are constantly being developed. 

 Research is now directed to developing a superior dental impression compound 

 using as the base carrageenin of carefully controlled properties. Agar and certain 

 forms of alginate serve this function. The market for carrageenin is stimulated by 

 the endeavor of manufacturers to develop a suitable form of extractive for specific 

 uses for which no currently produced type is satisfactory. 



Agar 



Agar, in the form of a sweetened and flavored gel, has been an important part 

 of the diet of oriental peoples for several hundred years. The accidental discovery 

 that agar can be piirified and dehydrated in one treatment occurred about 300 

 years ago when a Japanese innkeeper noticed that some agar gel he had discarded 

 during cold weather had frozen, and, upon thawing, lost most of its water 

 so that it dried readily in the sun to a fluffy white mass (Tseng, 1946), He found 

 that a gel could be made from it as easily as from the original seaweed. His dis- 

 covery led to the establishment (about 1769) and rapid growth of the agar in- 

 dustry in Japan. Dehydrated agar was easily and profitably exported. As early as 

 1903 there were 500 small agar factories in Japan with an average capacity of 

 about 4000 pounds per year each (Smith, 1905). Prior to World War II the 

 Japanese held virtually a world monopoly on the product. 



Definitions. The term, agar, is most frequently applied to gel-forming extractives 

 of red algae that are similar in properties, especially in gel strength, to the 

 Japanese product made principally from Gelidium amansii Lamour,** or to Cali- 

 fornia agar made from Gelidium cartilaginewn (L.) Gaill. It will always be 

 generic in common usage, and efforts to limit it to the extractives of two prin- 

 cipal Gelidium species are not likely to succeed. The following definition of agar, 

 the fundamentals of which were proposed by Tseng (1944), seems to be gen- 

 erally acceptable: Agar, the gel-forming extractive of Gelidium, Gracilaria, and 



" Gelidium corneum appeared early in the literature on agar as a principal source. 

 The name has been copied by successive authors and appears in government publications 

 and the U. S. Pharmacopoeia. However, agar has never been made from G. corneum and 

 it is safe to say that it never will be on a commercial scale. The species is so small and 

 the plants so scattered that it is inconceivable that sufficient quantities could be gathered. 



