Chemical analysis of tetrodotoxins in foods made using pufferfish ovaries pickled in salt and rice-bran

Food made by pickling pufferfish ovaries in salt and rice-bran is a tradition in Ishikawa Prefecture in Japan. The food is manufactured in two stages: curing in salt for a year and pickling in rice-bran for one or two years. Since pufferfish ovaries contain the potent neurotoxin tetrodotoxin (TTX), a toxicity test is imple-mented by mouse bioassay and only food that contains less than the quarantine limit (10 MU/g) are market-ed. However, testing by instrument analysis is internationally accepted for inspections for marine biotoxins including TTX. In the study, we developed a pretreatment method for TTX suitable for instrument analysis in food containing a large amount of salt, and then used the method to assess the level of TTX in food. Our experiments revealed that an activated charcoal cartridge is useful as the pretreatment method for TTXs in pufferfish ovaries: the recovery test of TTX using the food was 90%. We used the developed method to assess the level of TTX in commercially available foods made using pufferfish ovaries.