STUDIES ON AGAR-AGAR liN JAPAN * 

 By T. Yanagawa ^ and K. Tanii ~ 



Introduction 



Agar-agar, a kind of carbohydrate contained in red algae belonging 

 to Gelidium species, is one of the celebrated local products of Japan, 

 manufactured by a special process which was developed in this country 

 nearly 300 years ago. Numerous investigations have been made from 

 the point of view of both applied and pure science. 



We believe it advisable to commence with a brief description of 

 the customary method of manufacturing agar-agar in Japan (1). The 

 cleaned algae is first extracted with boiling water faintly acidified with 

 sulphuric acid, and by natural cooling of the extracted filtrate, agar- 

 agar hydrosol can be coagulated as a gel (1-2%). After it is cut pro- 

 perly it is placed outdoors in winter, so that the night cold freezes it, 

 while during the day the warmth gradually thaws the frozen ice into 

 water, which flows away. The last step is to dry it in the open air until 

 the product is obtained in a final dry form. Chemical changes in the 

 course of preparation have been investigated by Araki (2). 



The above-mentioned process takes more than half a month and 

 since it depends to a great extent on natural weather conditions, it 

 must be considered unsatisfactory. In order to remove this drawback, 

 several new methods have recently been devised, such as mechanical 

 freezing or the application of heat from hot springs. The main problems 

 to be solved are how to produce economically and efficiently a good 

 quality product by mechanical means and how to produce agar-agar 

 from Gracilaria confervoides by chemical treatment. 



I. Propagation of Seaweeds Used for Agar-agar 



Efforts have been made to promote the propagation of the seaweeds 

 which are used as the raw material of agar-agar. For instance, the reefs 

 were cleaned with simple implements so as to improve the production 

 capacity of the growing areas and the growing areas were extended by 

 submerging rocks and stones on the sea-bottom. Except in a few cases, 



• By courtesy of the Japanese Government, a Member Government of IPFC. 



' Doshisha University, Kyoto, Japan. 



' Northeast Sea Regional Fisheries Research Institute, Shiogama City, Japan. 



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