Nutritive Value or Toxicity of Oils of Salted and Dried Fishes

Sardine, mackerel, saury and similar kinds of fish are processed into salted and dried forms, a favorite item of Japanese diet. However, little attention has been paid to the nutritive value of protein or lipids which are contained in these products. While the nutritive value of proteins of the dried meat is not supposed to decrease in the result of processing or storage, the oils of dried fishes are rapidly autoxidized by the atmospheric oxygen. Therefore, an attempt has been made to examine the nutritive value of oil of salted-dried fishes by animal feeding, from which the following has been found. (1) As shown in Fig. 2, the oil extracted from salted-dried saury (Peroxide Value 65) indicated the toxic effects upon the growth of rats. However, the oil extracted from saury treated with butylated hydroxyanisol (B. H. A.) brought no retarding action to the rats. (2) The oil of salted-dried herring (Peroxide Value 14) had the good effects on the animal regardless whether or not it was treated with B. H. A. (Table 4). (3) The nutritive value of oil of dried mackerel (Peroxide Value 24) was slightly lower than that of B. H. A. treated oil (Table 5). With these findings in mind, it has been concluded that the nutritive value of oils of salted-dried fishes is influenced by degree of autoxidation, and if the original oil shows a high iodine number, the nutritive value becomes lower. However, when the antioxidant is applied to the material fish, the nutritive value remains as good as that of the original oil.