The contents of three sweeteners [acesulfame K (AK), saccharin (SA) and aspartame (APM)] in 203 samples of foods, either imported, purchased on a trip abroad, or made in Japan, were examined. In soft drinks, we detected both SA and APM in three samples manufactured in the U. S. A., AK and APM in three samples manufactured in the U. K. and only APM in three samples manufactured in Japan. In powdered soft drinks, we detected AK and APM, and SA and APM in British and Japanese products, respectively. In solid foods, we detected SA in three pickles and a confectionery (all Japanese-made). Confirmation of AK was carried out as follows: samples were dialyzed against 0.1N hydrochloric acid, and AK was extracted with ethyl acetate from the dialyzate. It was methylated with ethereal diazomethane, and analyzed by gas chromatography-mass spectrometry.
The effect of ratio of carbon dioxide and oxygen on the growth of 16 strains of food-borne pathogens and spoilage bacteria was investigated using the smear plate method. The results were as follows. 1) Growth of facultative anaerobic bacteria (A. hydrophila, B. cereus, E. coli, E. cloacae, L. monocytogenes, S. liquefaciens, S. typhimurium, S. aureus) was not completely inhibited by carbon dioxide, oxygen and their mixtures. However, the growth rate of those bacteria was reduced in proportion to the increase in the ratio of carbon dioxide in the gas mixtures. 2) Growth of microaerophilic bacteria (L. viridescens) was not affected by carbon dioxide, oxygen or their mixtures. 3) Growth of the five species (A. calcoaceticus, F. lutescens, P. aeruginosa, P. fluorescens, P. fragi) of aerobic bacteria was not recognized in the presence of 100% carbon dioxide, while M. luteus grew to some extent under the same conditions. Growth of P. fragi was inhibited in the presence of 30% or more carbon dioxide. The growth of F. lutescens was observed only in the case of 10% carbon dioxide and 90% oxygen. The susceptibility of aerobic bacteria to carbon dioxide was higher than that of facultative anaerobic bacteria and microaerophilic bacteria. 4) Growth of anaerobic bacteria (C. perfringens) was inhibited in the presence of oxygen regardless of its concentration. From these results, it is clear that carbon dioxide, oxygen and their gas mixtures can be used effectively to inhibit or delay bacterial growth.
A simple and rapid method was developed for the determination of enrofloxacin (ERFX), a new quinolone antibacterial agent, in fish and meat by high performance liquid chromatography (HPLC) with fluorescence and UV detection. The drug was extracted with 0.2% metaphosphoric acid-acetonitrile (7:3), followed by a Bond Elut C18 clean-up procedure. The HPLC separation was carried out on an L-column ODS using 0.05M sodium dihydrogenphosphate-acetonitrile (70:30) as the mobile phase at a flow rate of 0.5ml/min. The fluorescence detector was operated at the excitation wavelength of 285nm and the emission wavelength of 445nm, and the ultraviolet detector at 280nm. The calibration graph was rectilinear from 1 to 20ng. The recoveries at the level of 0.4μg/g were 80.2-85.4%, and the detection limit was 0.01μg/g. An excellent correlation was obtained between the results of the HPLC method and the bioassay method (r=0.99).