International Congress of Food Science and Technology , September , 1962 , London UTILIZATION OF CHLORELLA FOR FOOD

1962,London UTILIZATION OF CHLORELLA FOR FOOD Hisateru Mitsuda Laboratory of Nutritional Chemistry Faculty of Agriculture Kyoto University, Kyoto, Japan INTRODUCTION When we envisage the future of Japan with but a small land and limited natural resources on one hand and with a population about to reach one hundred million on the other, where to find protein resource poses one of the most serious problems to us. Our natural conditions are not favourable for stockraising, consequently its rapid development to meet the demand cannot be expected. We are not optimistic about the future of our fishing industry either in the face of deterioration of coastal fishing grounds and the ever increasing severity of international limitation on our deep-sea fishing. One may say that increased products of these animal proteins are important indeed, but utilization of vegetable proteins of high quality such as soy bean protein which is comparable with animal proteins, should be of equal importance. However, our supply of soybean is again heavily dependent on import. Pressed by these situations we have attempted to culture chlorella and torula yeast on a large scale, and accumulated basic data for rational utilizations of these resources for food. A part of these results is presented in the present paper. Studies on the utilization of chlorella for various purposes trace back to war time researches during both of the world wars in Germany and the United States. After the last war, the systematic research by Milner (1948) and Spoehr and Milner (1949) revealed the possibility of utilizing the algae for food if produced on a large scale, and stimulated studies on its mass culture in various countries. In Japan Tamiya’s group (Tamiya, Hase, Shibata, Mituya, Iwamure, Nihei and Sasa, 1953 and Tamiya, 1957) have succeeded in obtaining an yield of 15 to 19 grams of chlorella or scenedesmus per day per square meter in an open outdoor field with circulation. On the other hand studies on the nutritional aspect of chlorella, conducted in Japan by the Committee on The Essential Amino Acid Studies were rather disappointing since the dried algae was found to be hardly digestible and to cause diarrhea and other gastro-intestinal troubles due to its tough cell wall. Moreover, its dark greenish colour, due to an extremely high content of chlorophyll,and a strong unpleasant flavour seem to disqualify it as food. The results of experiments by Powell, Nevels and McDowell (1961) fully concur with the above findings. They have reported that chlorella, supplemented to any food gave a bitter, strong spinach-like flavour, and caused prominent gastro-intestinal symptoms. Methanol extraction, which has been employed to decolour the algae, has not been found effective in improving the digestibility either. Consequently for a satisfactory utilization of chlorella for food, the following must be achieved.. (1) Removal of the cell wall. (2) Removal of the strong colour and flavour to make it more palatable. (3) Thorough utilization of various components by separately extracting precious components such as folic acid, vitamin B12 chlorophyll, carotene etc. beside protein. DISRUPTION OF THE ALGAL WALL In these lines various treatments were tried to break the cell wall as indicated in Table 1 (Mitsuda,Kawai,Shikanai and Nakazawa, 1959 Table 1 The extractabilities of algal protein by various treatments