AGAR AND RELATED PHYCOCOLLOIDS 75 



and heated to the boiling point for a brief period in order to remove salts and 

 pigments. The water is then discarded and the wet seaweed conveyed to a cooker 

 where new water is added in the proportion of about 20:1 of dry seaweed. It is 

 cooked for about an hour by perforated steam coils in a tank with an opening at 

 the top. The contents of the cooker are conducted to a shaker screen, the agar 

 solution to a heated storage tank, and the seaweed residue to another cooker. 

 Filter aid is added in the storage tank and the solution goes through a filter press 

 and into 300-pound ice cans. The cans are stood in cold water to cool and gel 

 the solution, then placed in brine and frozen. When the seaweed residue is 

 cooked a second time, the insoluble portion (mostly cellulose) is so finely divided 

 that the ultimate residue is retained by the filter press. 



Blocks of frozen agar gel are removed from the cans and slid down an incline 

 to a large wheel, equipped with angular blades. As the wheel rotates, the ice 

 is shaven. Ice flakes are conveyed to a tunnel drier where they are spread evenly 

 to a depth of about 2 inches on screen-bottom trays. The trays are conveyed by 

 small carts through the drying tunnel against a current of hot air. The ice melts 

 vdthin the first 30 feet; dry agar sheets come out of the tunnel in a grinding room. 

 The dry, brittle sheets are hammer-milled and ready for market. Some agar is 

 finely pulverized for special purposes. 



The Agar Industry in Other Countries. Russia. Production of agar from 

 Ahnfeltia plicata (Hudson) Fries, and of an agaroid from Phyllophora rubens (L.) 

 Greville, was undertaken in Russia about 1930. The Russians learned of agar 

 possibilities from the Japanese of Karafuto, the southern part of Sakhalin Island, 

 located north of Japan, where large quantities of Ahnfeltia are found. The Sea 

 of Japan near Vladivostok, as well as the Archangel vicinity of the White Sea, 

 furnishes AJinfeltia in quantity. Phyllophora agaroid, produced in greater quantity 

 than Ahnfeltia agar, is obtained from raw material collected in the Black Sea near 

 Odessa. 



The process used to produce agar from Ahnfeltia in Russia differs in some re- 

 spects from that in the United States and Japan. It would appear that the Ahn- 

 feltia extractive is very easily affected by the procedure used in its preparation. 

 Dry raw material is first soaked in lime water for 3 days. It is then cooked for 10 

 hours in the ratio of 1 part dry seaweed to each 15 parts, by weight, of a solu- 

 tion of 5 per cent calcium oxide. Extraction with the pH at neutrality results 

 in an agaroid (low gel strength agar), while the extractive will fail to gel entirely 

 if the pH is on the acid side. Since pressure cooking is also harmful to the gel 

 strength, open boiling is preferred. The presence of neutral salts tends to reduce 

 the quality of the agar by increasing the ash content, although they do not affect 

 the yield. Decolorization of the agar is eflFected by the addition of activated carbon 

 just before filtration. Slow freezing is best as the ice crystals formed tend to be 

 larger; melting is done at 35.6 to 41° F to keep reabsorption of the water to a 

 minimum. The wet agar flakes are further washed in large quantities of cold water. 

 According to Kizevetter (1941), Ahifeltia agar "equals the high grade agar made 

 abroad, and in some respects excels it." 



Russian scientists have published many reports (Dokan, Elin, Kizevetter, 

 Koryakin, Zhelezkov ) on the technology, manufacturing processes, chemical nature, 

 physical properties, and various uses of Russian agar and agaroid. 



