種々のクロルテトラサイクリン(CTC)処理方法による底引漁獲物の鮮度保持効果および各処理魚体内の CTC 分布

Immediately after being caught butter fish and lizard fish were subjected to various CTC-treatments aboard a bull trawler, “Akashimaru No. 96”, and stored in plain or CTC ice in a fish hold of the boat for 16 to 19 days. The CTC treatments employed were (1) CTC-icing (4.5ppm CTC), (2) two-minute dip in sea water solution of CTC and (3) showering a 25-kg lot of fish with a one liter aliquot of the solution. The volatile bases nitrogen (VBN) and CTC residue were determined after landing by the microdiffusion method5) and the cylinder plate assay method4), respectively. The butter fish stored in plain ice without prior CTC treatment showed incipient spoilage, whereas those held in CTC-ice were judged to keep a passable quality. The quality of the fish stored in CTC-ice was better than that of spray-treated fish and comparable with that of dip-treated in a 10 ppm CTC solution. In dip-treated group, the fish quality was fairly improved with the increase in the CTC concentration. The CTC residue was found about 0.1 ppm in the flesh of butter fish when sprayed with a 80 ppm CTC solution, dipped in a 40 ppm CTC solution and/or CTC-iced. The CTC residue was highest right under the skin, decreased sharply with the depth of flesh, and not existed in deeper part than a 5-mm distance from the skin. In case of lizard fish, the effectiveness of the CTC treatment was not so marked. The CTC residue in this fish was far smaller than that in butter fish though the vertical distribution pattern of CTC in the flesh was similar each other. Under the present experimental condition, the CTC residue varied linearly with the CTC concentration of the solution for the dip or spray treatment, and logarithm of the residue in the flesh showed a linear relationship with logarithm of VBN of the flesh. These relationships suggest that passable quality (VBN, 25mg%) of any fish comparable to butter fish in size and shape will be resulted from keeping CTC residue at a 0.1 ppm level which can be achieved by such treatment aboard the boat as a dip in 20 to 40 ppm CTC solution or a spray with solution of CTC concentration higher than 80 ppm.