68 MARINE PRODUCTS OF COMMERCE 



agar from the raw material; the yield obtained ordinarily represents an optimum 

 with respect to the cost of production. The optimum is established by the efiB- 

 ciency of the production process. 



Although all seaweeds probably vary with the season in phycocolloid content, 

 little experimental data are available on the subject. Aoki (1940) found that in 

 Japan Gelidium amansii has the highest agar content in the spring and the lowest 

 in summer when most of the harvesting is done. Apparently the phycocolloid con- 

 tent is greatest during or immediately after the season of most rapid growth. This 

 varies among species and with locality as well. 



Grading of Finished Product. Management of agar production is vested in the 

 Japan Agar Control Company, a government agency founded in 1938 (Adams, 

 1947) . This organization grades all agar produced in Japan on the basis of moisture 

 content, color, gel strength, insoluble matter, protein content, solubility, and other 

 characteristics. 



Gel strength is determined by placing a 1.5 per cent solution of agar in a 

 small cup and allowing it to stand overnight at room temperature. A 100-gm 

 weight that has a cylindrical, flat tip 1 square centimeter in area is placed upon 

 the surface of the agar. If the tip does not rupture the gel surface, the agar is 

 graded as No. 3, or better. Similarly, grade 2 must support a 200-gm weight and 

 grade 1 a 300-gm weight. Agar that does not meet grade 3 requirements, or better, 

 is not exported. Table 5 shows the standards that the three grades of Japanese 

 agar must meet. 



Table 14. Characteristics of the Three Grades of Agar Exported by Japan.* 



( Gel strength here is the number of grams supported by 1 sq cm of gel surface when 

 the weight indicated is added all at once.) 



The wide range of variation of all the characteristics in Japanese agar is due 

 primarily to the mixing of different species of seaweeds in different proportions 

 (Table 13) and secondarily to the great number of agar factories, each with its 

 own modification of the production process. A slight variation in pH during cook- 

 ing has considerable effect upon gel strength. If the pH is relatively more acid, 

 gel strength will be low, but extraction will be rapid and more thorough. Some 

 species of seaweeds are more affected by a low pH than others. 



Production and Export Data. Production of agar in Japan has risen steadily 

 since its origin, especially from 1926 until 1940. During the war years there was 

 a sharp decline. From 1926 until about 1933 over 75 per cent of Japan's agar 

 production was exported. After 1932 home consumption increased at a much 

 greater rate than exports, which actually declined from 1936 through 1945. In 

 1946 exports rose again along with production and were expected to reach normal 

 by 1950. Production figures for 1926 through 1945 are given in Table 15. 



* Adams, 1947. 



