Free amino acids, oligopeptides, organic acids and nucleotides of ISHIRU (fish sauce)

Two kinds of fish sauce ISHIRU made from squid liver and sardine are produced in Note peninsula of Ishikawa prefecture. This ISHIRU, as well as SHOTTURU in Akita and IKANAGO SYOYU in Kagawa, is very famous as one of three major fish sauces in Japan. In this study, free amino acids, oligopeptides, organic acids, nucleotides of ISHIRU were analyzed, and their characteristics related to the taste of ISHIRU were discussed. The results were as follows : (1) ISHIRU contained large amounts of total nitrogen and salt. (2) The major organic acids of ISHIRU were lactic acid, pyroglutamic acid, acetic acid, formic acid, succinic acid, melic acid and so on. (3) ISHIRU contained large amounts of free alanine,glutamic acid, glycine, lysine and valine. (4) The constituent amino acids of oligopeptides in ISHIRU were glutamic acid, glycine, aspartic acid and lysine. (5) Adenosine-5'-monophosphate (AMP), inosine-5'-monophosphate (IMP) and guanosine-5'-monophosphate (GMP) were not detected in ISHIRU. From these results, it is presumed that the characteristic taste of ISHIRU is extensively related to the contents and proportions of free amino acids, oligopeptides and organic acids, but nucleotides hardly contribute to its taste.