かつお節のシラタに関する研究-V

Abstract

Following the preceding work, the content of inosinic acid in katsuobushi was determined by ion exchange chromatography using Dowex 1-× 4 resin both on the shirata and on the normal portion of the katsuobushi. According to the result obtained, inosinic acid is always less in the shirata portion than in the normal portion (cf. No. 5, Table 1), and as has been reported by other authors2), 4), there is a wide variation in regard to inosinic acid content of individual katsuobushi (Table 1). Therefore it seems that the shirata has some relation to the destruction of inosinic acid. The phenomenon of shirata, however, occurs firstly in the hypodermic tissue of katsuobushi and then it gradually develops in the deeper layers. Furthermore, the data on the distribution of inosinic acid in normal katsuobushi, not affected by shirata, show that inosinic acid always exists in larger amounts in the portion near the backbone than in the portion near the skin (cf. No. 6, 7, Table 1). Therefore the difference in inosinic acid content between the shirata and the normal portion of the katsuobushi is not the result of the shirata but is the result of sampling. The problem of whether the stock made from shirata is inferior or not to that made from normal katsuobushi is rather complicated. When the tissue of katsuobushi disintegrates into shirata its amino acid content decreases. In this case, if the katsuobushi contains less inosinic acid, its stock may be inferior to that made from normal katsuobushi, but when the katsuobushi contains much inosinic acid, the diminution of the amino acid may have little influence upon the taste of stock.