The present examination was undertaken to research the distribution of enteropathogenic E. coli in marketing foods. The total 160 samples of commercial ground pork, chicken and oyster were examined from July 1969 to 1971. The results are summerized as follows; 1. The rate of positive samples of enteropathogenic E. coli observed were 5/66 (7.6%) of the pork, 3/34 (8.8%) of chicken, 19/60 (31.6%) of the oyster. Isolates were identified by biological and biochemical tests, as well as by serotyping as enteropathogenic E. coli. 2. Detection of enteropathogenic E. coli in ground pork had been proved to be higher frequency in summer than in winter. 3. Serotype of isolates and their distribution rates were E. coli O 55 (3.6%), O 86a (3.6%), O 86 (3.6%), O 112ac (3.6%), O 119 (10.7%), O 125 (7.2%), O 126 (42.8%) and O 128 (21.4%) respectively, and a large number of strains of O 126 and O 128 were isolated from oyster. 4. One oyster retained two types of enteropathogenic E. coli.
In recent years plastic films have become widely used for food packaging. Further, there are many cases where different types of plastic are laminated or plastic are coated or laminated on paper or metal foil. Among these, there are few cases that toxic additives may be present. Hence, there is a need to discriminate the types of packaging material in order to assure the safety of foods. However, with the existing transmission of IR, the absorption band might become complicated by the lamination or, in case of laminated paper or metallic foil, determination becomes impossible. Hence, a discrimination of packaging material by Attenuated Total Reflex (ATR) spectrum method was performed. By measuring the transmission and the outer and inner sides of IR it is possible to determine the types of plastic laminated. This method was especially effective in the identification of paper or metallic foil laminated with plastic. From the results of measurements made on about 100 packaging material of foods it was found that polyethylene was used most in contact with food, followed by polypropylene. There were no cases where polyester or polyamide was used in direct contact with foods.
There have been many reports on the presence of nitrosamines in foods, but the methods of extraction and identification have not always been adequate and some of the results have been conflicting. The authors tried to detect nitrosamines in 149 samples of Japanese commercial food, and dimethylnitrosamine (DMNA) and diethylnitrosamine (DENA) could be identified in 15 samples. Extraction was carried out by modified procedure of Howard method and identified by thin-layer chromatography. Recovery of extraction of DMNA from foods by the above modified method was 50-60% and the detection limit on TLC plate was 0.2μg of DMNA with ninhydrin. DMNA was detected in 6 among 20 samples of the pressed ham, which materials were pork, whale and (or) tuna meat, and also detected in 1 sample among 3 samples of hamburger consisted of pork and whale meat. Although DMNA and DENA were detected in 7 among 20 samples of salted salmon roe in which sodium nitrite was used as a color fixative, these contents were trace. The amounts of DMNA in the pressed ham could not be exactly determined by TLC method, but from the detection limit on the plate the contents were presumed to approximately as 15-25ppb. In salted cod roe purchased in markets, no nitrosamines were detected, but nitrite-treated cod roes which were processed in our laboratory showed over 1 ppm of DMNA and DENA contents. This fact indicates that the addition of nitrite to secondary amine-rich foods, such as fishes, fish roes or whale meat may be possible hazard to human health.
Gas chromatographic analysis of patulin was carried out using patulin and its derivatives, trimethylsilyl ether and acetate. The results showed that in highly contaminated samples, quantitative and qualitative measurements of patulin were possible without making the derivatives, while in lowly contaminated ones, the derivative formation was desirable. Silyl ether of patulin gave the best response in the examined derivatives. The acetate of patulin was sensitive and more than 90% of patulin was acetylated within 4 hours after the addition of reagent. As patulin was markedly colored by the addition of trifluoroacetic anhydride and pyridine, trifluoroacetylation rate could not be tested. Furthermore, several kinds of solvent systems for the extraction of patulin from rice and the clean up method of the extract for gas chromatography were examined. Good recovery was obtained by the extraction from rice with the mixture of ethyl acetate and water (71.8%), and then the loss of patulin in clean-up procedure by silica gel chromatography with n-hexane-methanol was negligible.
In the previous papers, the authors reported on gas chromatography of patulin and gas chromatographic analysis on its presence in rice. In this papers, gas chromatographic analysis of penicillic acid and its derivatives, trimethylsilyl ether, acetate and trifluoroacetate were examined. Trimethylsilyl ether of penicillic acid was most sensitive among these derivatives, and also the peak on the gas chromatogram was completely separated from that of patulin. Therefore, multidetection of both mycotoxins became possible. The acetate gave good response and about 50% of penicillic acid unreacted was present after 4 hours of acetylation; however, more than 90% of the acid was acetylated after 24 hours of the reaction. In comparison with trimethylsilyl ether, trifluoroacetate did not give a desirable response and always gave two peaks on gas chromatogram. Furthermore, analytical study of penicillic acid in rice was examined. Extraction of penicillic acid from the sample added penicillic acid with the mixture of ethyl acetate and water (7: 1) gave good results and its recovery was 97.1%.
It was already clarified that the isolates of Staphylococcus aureus, which had been implicated in food poisoning outbreaks, were strictly restricted to the organisms belonged to the coagulase types II, III, VI or VII. In this investigation, a total of 3, 590 specimens consisted of 720 foods, swabs of 280 chopping boards, swabs of 280 table wares, swabs of fingers of 470 food handlers, and 50 nasal swabs and 1, 790 feces obtained from healthy human was examined for the presence of S. aureus. Serological classification of the isolates was also made by means of the coagulase typing procedure. Results obtained are summarized as follows: 1) A total of 471 strains of S. aureus was isolated from the above mentioned specimens throughout the investigation. 2) Detection rates of the organism were varied according to the specimens, i. e., 15% from foods, 9.3% from swabs of chopping boards, 5.4% from swabs of table wares, 26.0% from swabs of food handlers' fingers, 13.2% from nasal swabs and 10.8% from healthy humans feces, respectively. 3) All the isolates were typed into 7 coagulase types, viz., 17 isolates as type I, 54 as type II, 82 as type III, 101 as type IV, 54 as type V, 52 as type VI and 111 as type VII, respectively. 4) From the viewpoint of food poisoning prevention, it was noteworthy that 75 out of 108 (69.4%) isolates from food, 22 out of 26 (84.6%) from chopping board, 82 out of 122 (67.2%) from food handlers' finger and 20 out of 29 (68.9%) from feces of healthy humans were the organisms belonged to the coagulase types II, III, VI or VII, since these are regarded as a causal agent of staphylococcal food poisoning.
The determination method of nitrate nitrogen in foods provided in the A.O.A.C. is based on either the colorimetric method by m-xylenol, or the reduction method by cadmium. However, there are some problems in the reproducibility and simplicity of these methods. The sodium salicylate method was studied and it was found that this method was more excellent than the other methods. The procedure of this method is as follows. Extract nitrate nitrogen in foods with distilled water at room temperature, the added 1ml of 20% phosphotungstic acid solution if the sample has more protein. Take an aliquot of the extracts containing 5-20μg of nitrate nitrogen and add 1ml of 1% sodium salicylate-sodium hydroxide solution, 1ml of 0.1% ammonium sulfamate and 1ml of 0.2% sodium chloride, then heat the mixture to driness on a water bath. Add 2ml of concentrated sulfuric acid and 20ml of distilled water to the residue, extract with 20ml of methyl isobutyl ketone. To the organic solvent layer add 10ml of 1% sodium hydroxide solution and transfer sodium hydroxide layer to a 50ml Nessler tube, then dilute to 30ml with distilled water. Measure the absorbance at the wavelength of 415mμ. The recovery ratio was about 90% in the addition experiment to vegetables and meat products.
Hydrogen peroxide is used in Japan as bleaching or sterilizing reagent to fish-paste products and boiled noodle. On the other hand, hydrogen peroxide is also used as oxidizing reagent in the field of organic chemistry. These are suggesting that oxidation or decomposition of the food components and production of abnormal substances in food may be given by treating with hydrogen peroxide. Accordingly, the study was carried out on the inhibition effects of Escherichia coli K-12 (E. coli) with oxidation products of 12 kinds amino acids which were produced by treatment with hydrogen peroxide. Namely, 2g of each amino acid was oxidized with 40ml of 5% hydrogen peroxide at 37°C for a week and then filled up to 200ml with water after the hydrogen peroxide was decomposed with manganase dioxide. The growth of E. coli was inhibited by the presence of the oxidation products of glycine, L-histidine, L-leucine and L-tryptophan, respectivly. The effects of the other eight kinds of amino acids were also examined, however, these oxidation products affected little on the growth of E. coli.
Fungal content of 24 samples of various types of spices of which a half was domestic and the others were collected from the markets in U.S.A., was surveyed from the hygienic point of view on foodstuffs. From 15 mold-positive samples, 12 were estimated under heavy contamination. Twenty eight fungi were isolated from these spices and were identified. Except a few Fungi Imperfecti and Mucorales, the majority of the species was found to be belonging to the genera Aspergillus and Penicillium. In the genus Aspergillus, the members of A. glaucus, A. flavus, A. niger, A. terreus and A. versicolor groups were the predominant species on the Japanese samples. In Penicillium, the series commonly found was P. chrysogenum only appearing in paprika of Japanese sample. The important contaminants in U.S.A. samples were identified as representatives of the A. glaucus group. No aflatoxins were detected in CHCl3 extracts of the rice culture of A. flavus which were found in Japanese sage and pepper. Since some spices such as garlic powder are known to have a bacteriostatic or bacteriocidal property, it may be suggested from the result obtained that some spices are not subject to spoilage.
Acute toxicity and moldstatic activity for Asp. niger of transformation products of dehydroacetic acid were investigated. And the results obtained were as follows: 1) The moldstatic activity of each compounds compared with dehydroacetic acid were found to be 1/15 of dehydroacetic acid in strength for diacetylacetone, 1/30 for 2, 6-dimethyl-4-pyrone-3-carboxylic acid, and 1/180 for 2, 6-dimethyl-4-pyrone. 2) On acute toxicity, the oral LD50 (and 95% confidence limits) in mice were found to be 1.33g/kg (1.23-1.44g/kg) for dehydroacetic acid, 2.33g/kg (2.04-2.65g/kg) for 2, 6-dimethyl-4-pyrone-3-carboxylic acid, 1.67g/kg (1.49-1.88g/kg) for 2, 6-dimethyl-4-pyrone, and 0.65g/kg (0.59-0.72g/kg) for diacetylacetone.