1957 Volume 10 Issue 3 Pages 87-93
Large scale studies made by the Taiyo Fishing Company in the last two years confirmed the economical value of fish preservation with chlortetracycline. In the main part of these studies the fish were preserved in the boat with crushed ice containing chlortetracycline at 5 mcg/g, and the amount of fish wasted was reduced to less than half of the control without chlortetracycline. Prior to the study presented in this paper, a method was required to determine the amount of chlortetracycline contained in fish meat preserved with chlortetracycline ice. The cylinder plate method or the turbidimetric method used for the determination of chlortetracycline in a drug gives the exact value, but it is limited to the determination of the material containing this antibiotic at not less than 5mcg/g. Ogata1) has devised a paper disk method which can measure chlortetracycline as low as 0.06–0.125mcg/g. The plate method with Bacillus cereus published by the Food and Drug Administration, U.S.A.2) is described as being able to measure an antibiotic as low as 0.005–0.01mcg/g. The authors traced these two methods, and, on the basis of the combination of the principles in these two methods, the plate method presented in this paper was established. In this method, 0.03 mcg/ml solution exhibits the inhibition diameter of 13.8 mm, and 0.06mcg/ml that of 17mm. This method, being combined with the extraction procedure with acid acetone, gave the relatively accurate value of chlortetracycline contained in the fish meat to which a known amount of chlortetracycline had been injected.
Since the method of determination of chlortetracycline at a low concentration was estabished, the authors examined the amount of the antibiotic in the fish preserved with the chlortetracycline ice. For this purpose, it was necessary to prepare ice in which an exact amount of the antibiotic was evenly distributed. During studies on the preparation of ice, the authors confirmed Tarr’s observation3) that something in water quickly inactivates chlortetracycline. The authors found that the most important point in the preparation of chlortetracycline ice is to eliminate the chlorine in the water. In the experiment preserving fish with distilled water ice containing chlortetracycline at 5mcg/g for 12 days, the authors determined the amount of chlortetracycline contained in the skin and the meat. The maximum amount in the skin was 0.005mcg/g, and that in the meat less than 0.005mcg/g. The authors measured the antibiotic in fish which had been preserved with chlortetracycline ice for from 8 to 17 days. This ice was prepared by dissolving chlortetracycline at 5mcg/ml in the city water, but the activity was reduced to 1.3mcg/g. The maximum amount of chlortetracycline in the skin was 0.05~0.14 mcg/g (0.01~0.03 mcg/cm2), and that in the meat was 0.06mcg/g. The number of bacteria and ammonium nitrogen in the fish meat which will be reported in another paper by Higashi and others indicated that the fish preserved with the chlortetracyclne ice were fresher than the control with the ordinary ice. It was suggested that a careful determination of chlortetracycline in the ice and the use of ice containing an exact amount of the active antibiotic would increase the effect of the antibiotic for fish preservation.