Formation of methylguanidine, a mother substance of N-nitrosomethylcyanamide and N-nitrosomethylurea, in smoked-dried skipjack sticks, "Katsuo-bushi".

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  • かつお節におけるメチルグアニジンの生成について
  • かつお節におけるメチルグアニジンの生成について〔英文〕
  • カツオブシ ニ オケル メチルグアニジン ノ セイセイ ニ ツイテ エイブン

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Abstract

It has been reported that smoked-dried fish sticks such as “katsuo-bushi” and “kezuri-bushi” contain comparatively large quantities of methylguanidine (MG; 18-178mg/kg). The present study was to elucidate the mechanism for MG formation in “katsuo-bushi” and its related products. MG and its precursors, creatine (CRE) and creatinine (CRN) were analyzed in the “katsuo-bushi” samples obtained at different preparation steps. Small amounts of MG (1.3-2.9mg/kg) were detected in boiled and semi-dried fish fillets called “namari-bushi”, although no appreciable amount of MG could be detected in raw skipjack muscles. The moisture content of the fish sticks gradually decreased as the manufacturing steps advanced, while in contrast, the MG content of the products increased. The degree of catalysis on the oxidation of CRE and CRN to give MG that could be observed in the presence of metal pieces such as copper and iron, was almost negligible, but the presence of certain metallic ions such as Cu+, Cu++ and Fe+++ apparently enhanced MG formation. This catalytic effect was conspicuous under acidic conditions. MG formation occurring in the boiling process of fish fillets in an iron kettle or tank seemed to be due to the catalytic action of Fe+++ derived from iron-rust.

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