We have investigated the control of halophilic histamine-producing bacteria, Photobacterium phosphoerum and Photobacterium damselae by using vapor of essential oils and other agents. Three of fourteen essential oils showed high antibacterial activity against histamine-producing bacteria. Among food additives and detergents, ten of twenty-one food additives and seven of nine detergents also showed antibacterial activity. Low concentrations of sodium chloride suppressed the growth of both species. We examined the resistance of these bacteria to dryness on food contact surfaces. After 0.5 hours, no viable cells were detected. So, the bacteria were sensitive to dry conditions. These results should contribute to development of the techniques to prevent histamine food poisoning.
2-Alkylcyclobutanones (ACBs) are specific radiolytic products in irradiated lipid-containing food and can be used to detect irradiation of foodstuffs. EN1785, a European Committee Standardization Method, can detect 2-dodecylcyclobutanone (DCB) and 2-tetradecylcyclobutanone (TCB), which are ACBs, using GC/MS, thereby allowing judgement as to whether foodstuffs have been irradiated. In this study, the performance of EN1785 as a qualitative test in a single laboratory was evaluated and its applicability to beef, pork, chicken and salmon was verified. In the performance evaluation test, lipids extracted from unirradiated food using the Soxhlet extraction method were used as negative samples. Further, negative samples, to which DCB and TCB were added at 0.05 μg/g lipid (equivalent to the amount generated in food when irradiated at 0.5 kGy or more), were used as positive samples. For each food type examined, 4 negative and 16 positive samples were analyzed by EN1785 to verify the method's ability to detect irradiation. All of the negative samples were judged negative and all of the positive samples were judged positive. Thus, the method should be able to detect irradiation in beef, pork chicken and salmon irradiated at 0.5 kGy or higher. Next, to confirm that this is the case, the same types of food examined above, both unirradiated and irradiated at doses of 0.5-4 kGy, were analyzed by the method. All of the unirradiated samples were judged negative and all of the irradiated samples were judged positive. In a laboratory different from the one where the aforementioned evaluation was conducted, a performance evaluation test was carried out. Blind coded samples, including unirradiated and irradiated samples, were then analyzed in the laboratory according to EN178S. Ten samples (2 unirradiated and 8 irradiated samples) were analyzed for each type of food and the verified method was found to be 100% accurate. Even after the irradiated foodstuffs had been frozen for 6-9 months, it was still possible to judge whether the foodstuffs had been irradiated or not using the EN1785 method.
We investigated the determination of spinosyn A and spinosyn D, the active ingredients of spinosad, in animal and fishery products by liquid chromatography with mass spectrometry (LC-MS). The sample was homogenized with 1 mol/L dipotassium hydrogenphosphate aqueous solution and extracted with acetone-n-hexane under mildly alkaline conditions. After n-hexane-acetonitrile partitioning using an EXtrelut® column, the extract was cleaned up on a tandem SAX/PSA mini-column, and examined by means of fragmenter-voltage-switching ESI-SIM mode LC-MS. Mean recoveries (n=5) of spinosyn A and spinosyn D from eleven kinds of fortified samples at the analyte concentration of 0.01 μg/g and 0.05 μg/g ranged from 76.1% to 93.8% (RSD≤8.7%) and from 75.1% to 104.1% (RSD≤8.6%), respectively.
A rapid and simultaneous method by using inductively coupled plasma mass spectrometry (ICP-MS) was developed for determination of 19 elements in infant formula. Fast and efficient sample digestion was achieved by a microwave-assisted nitric acid procedure. An acetic acid was added to both these treated solutions and standard solutions as a countermeasure for carbon charge transfer in As, Se elements. The observed calibration curves showed good linearity (r2>0.9993) and the quantification limit was low. The recoveries of elements were 95.0-108% and the relative standard deviations (RSD) of this method were 0.3-4.2%. The analyzed values were in good agreement with the certified values in a NIST standard reference material. This study showed that the ICP-MS method is useful for major to trace multi-elemental determination in infant formula.
We investigated the antibacterial activity of food additives and detergents against histamine-producing bacteria on food contact material surfaces. Based on minimum inhibitory concentration (MIC) testing with Morganella morganii NBRC3848, Raoultella planticola NBRC3317 and Enterobacter aerogenes NCTC10006, we screened nine food additives and four detergents with relatively high inhibitory potency. We prepared food contact material surfaces contaminated with histamine-producing bacteria, and dipped them into fourteen agents (100 μg/mL). Sodium hypochlorite, benzalkonium chloride, benzethonium chloride, n-hexadecyltrimethylammonium chloride and 1-n-hexadecylpyridinium chloride showed antibacterial activity against histamine-producing bacteria. We prepared low concentrations of the five agents (10 and 50 μg/mL) and tested them in the same way. Sodium hypochlorite showed high antibacterial activity at 10 μg/mL, and the other four showed activity at 50 μg/mL. So, washing the material surface with these reagents might be effective to prevent histamine food poisoning owing to bacterial contamination of food contact surfaces.
A method for identification of fish species using three different mitochondrial DNA regions, 16S rRNA, cytochrome b and cytochrome c gene fragments, was investigated. The combined use of all three regions enabled reliable species identification in not only raw fish, but also dried, seasoned and boiled fish, products. Furthermore, the method was applicable even to vomitus from a patient involved in a puffer fish poisoning incident. However, further improvement is necessary to discriminate between closely related species such as Takifugu rubripes and T. chinensis, because they showed close similarity in the nucleotide sequences in the three gene fragments analyzed in this study.
Overseas and imported mineral waters were subjected to visual examination, tested for standard plate count and heterotrophic bacteria, and also analyzed to determine the concentrations of several anions and cations. Some products showed turbidity or color, and several had standard plate count and/or heterotrophic bacteria. One imported natural mineral water product had a high level of standard plate count, and the levels differed with the lot. Tests for total coliform bacteria, Escherichia coli, fecal streptococci, and Pseudomonas aeruginosa were negative on additional testing of samples having standard plate counts of more than 100. The fluoride concentration of one European region sample exceeded the production standard of the Food Sanitation Act in Japan (raw water: less than 2 mg/L) and most of the products lacked the warning labels which are mandatory for fluoride concentrations over 0.8 mg/L. These results indicate that none of the raw water for mineral waters was seriously polluted, but insufficient sterilization of the bottle or cap or contamination with air-borne microbes during the production process was probably responsible for the pollution. Attention needs to be paid to fair labeling, such as no sterilization/no sterile filtration and high fluoride concentration.
The determination of five drugs, fenfluramine (FEN), N-nitrosofenfluramine (NFE), sibutramine (SIB), mazindol (MAZ) and phenolphthalein (PHP), was studied in slimming health foods using GC-MS/MS. These drugs have been detected at high rates, especially in slimming health foods. Prolonged or excessive consumption of non-approved or unauthorized pharmaceuticals may cause serious adverse health consequences. In this study, samples were extracted with methanol and ultrasonication. Analyses were performed by GC-MS/MS, using established MS/MS parameters in the electron ionization (EI) mode and chemical ionization (CI) mode. In the EI mode, the recoveries of five drugs from several types of slimming health foods such as tablets, capsules and tea-bags spiked at 1 μg/mg (except PHP, spiked at 4 μg/mg) were in the range of 85.0-110.7% and 100 μg/mg (except PHP, spiked at 200 μg/mg) were 94.9-102.9%, respectively. In the CI mode, good recoveries of 80.3-102.2% (spiked at low concentration) and 92.8-103.2% (spiked at high concentration) were also obtained. We evaluated the present method using four slimming health foods, in which drugs had previously been detected. The results were similar to the previous results. These findings indicate that the present procedure for evaluating five drugs in slimming health foods by means of GC-MS/MS is useful.
The performance characteristics of an analytical method for cyanogenic compounds were evaluated. Specifically, we tested the trueness, repeatability and intermediate precision of the method using a spectrophotometric-based detection system for 4-pyridinecarboxylic acid and pyrazolone after steam distillation. The pH adjustment of the distillate was revealed to affect the trueness of the measurements. A pH of approximately 6 was found to be optimal. The targeted quantitation limit of the cyanide ion was set to 5 mg/kg. The performance of the method was evaluated using beans spiked with cyanide ion at one to two times the quantitation limit (5-10 mg/kg). The trueness of the method was between 78-90%, and the repeatability and intermediate precision were between RSD 1.2% to 6.0%. A surveillance of cyanogenic compounds in beans retailed in Japan was then carried out. All the results were below the quantitation limit of 5 mg/kg.