Abstract
The present study was carried out in order to obtain data which will be able to prove the safety of chlortetracycline as a food additive when employed in keeping quality of sockeye salmon.
The sample fish were caught on May 24, 1958, by the gill net in the Behring Sea area and immediately after receiving aboard a factory ship they were dipped for 30 minutes in chlor-tetracycline (10ppm)-sea water. The fish were frozen and kept thereafter at about -20°C. The sample fish were landed at Tokyo port two weeks later and carried over to our laboratory by air. Various tissues were assayed for CTC by TOMIYAMA et al's cylinder plate method7).
It was observed that not only the skin but also the operculum, the fin and the gills con-tained a large amount of CTC whereas the flesh only less than 0.13 ppm and the gut less than 0.01 ppm. The assay for CTC in several thin layers of flesh under the skin revealed that no penetration of CTC occurred in flesh deeper than 3 to 4mm from the skin under the present experimental condition. The canning of the treated fish inactivated the penetrated CTC com-pletely. Such cooking procedures as boiling, broiling and frying also destroyed the CTC resi-dues on fillets cut from the treated fish. It was clearly shown that the rate of inactivation of CTC at 95-99°C. conformed with the first order reaction.
Based on the present data as well as recent literatures on the toxicity of CTC and iso-CTC, emergence of CTC-resistant strain and anaphylactic reaction due to long-term ingestion of low-level of CTC, the present discussions have disclosed the safety of CTC when employed for keeping freshness of sockeye salmon.
