The 4-amino-3-hydrazino-5-mercapto-1, 2, 4-triazole (AHMT) method was superior to acetylacetone method and chromotropic acid method for the direct determination of formaldehyde in Lentinus edodes. By applying this method to raw and dried samples, it was found that the free formaldehyde content varied with both the strain and the fruiting season. The contents found were higher than those given in other reports and, in the autumnal strains, did not increase after drying. In addition, the formaldehyde formation by enzymatic and acid hydrolysis also depended on the strain and fruiting season. Further studies are required to identify the precursor of formaldehyde in Lentinus edodes.
It was found that three of fifty-one strains of A. ochraceus group fungi isolated from green coffee beans produced ochratoxin A (OCT-A). One of these three strains and another isolated from barley produced high levels of OCT-A. Several of the twenty-seven single-spore isolates derived from these two strains showed stable and high production of OCT-A. A 300ml Erlenmeyer flask with 30g of polished rice and 12ml of water was autoclaved, then inoculated with A. ochraceus and incubated for 2 weeks at 25°C. These conditions were optimum for toxin production. The methods for extraction, column chromatography, crystallization, etc. were examined, and suitable procedures to obtain pure ochratoxins from the moldy rice were established. Large amounts of crystalline OCT-A and B were easily obtained. Studies on the bioactivity of OCT-A are in progress.
The procedures (purification, developing solvent, medium) used in the original thinlayer bioautographic method of Donoho and Kline for the determination of monensin in chick tissues were modified to improve the recovery and sensitivity of the assay. Recoveries of monensin from fortified tissue samples were 92.9% from fat, 86.0% from liver and 104.4% from muscle. The assay sensitivity was improved to give a detection limit of 0.01ppm in fat and 0.0125ppm in other tissues. Feed containing monensin at 80, 100 or 120ppm was given to chicks for 9 weeks, and the residual levels of monensin in tissues were assayed. The residual levels of monensin at 0 hour after withdrawal were 0.057 to 0.110ppm in fat, none to 0.035ppm in muscle, none to 0.039ppm in liver and none to 0.014ppm in kidney. No detectable amount of monensin was found in fat at 48 hours or more after its withdrawal from the feed, or in liver, muscle and kidney at 24 hours or more after withdrawal. When monensin was given for seven days at significantly higher levels (300 and 600ppm) than recommended, the tissue levels did not increase proportionally with the levels in the feed. The half-life of monensin disappearance from fat was estimated to be 3.4 to 4.0 hours.
During the period from February through April, 1979, commercial beers of different types obtained from retailers in Tokyo were examined for the presence of volatile N-nitrosamine (NNA). Detection and determination of NNA were carried out by the use of a thermal energy analyzer coupled with gas chromatography. It was found that 25 (93%) of 27 samples contained dimethylnitrosamine (DMNA), with a mean level of 1.7ppb; no other NNA was detectable. The source of the DMNA was investigated, and it was found that relatively high levels of DMNA contamination of malt occurred when the green malt was dried and/or kilned with fuel gas, while lower levels were found in green malt treated with an electric desiccator.
Microbiological examination of chilled potato and macaroni salad (20 samples) and Chinese dumplings (“Gyoza”) (19 samples) was carried out to examine the microflora, especially the yeasts, of these market foods. The samples were corrected from retail markets by official food examiners and investigated by the official microbiological methods. Counts of bacteria, yeasts and fungi in the salad samples were found to range from 103 to 105, 101 to 105, and below 103 per gram, respectively. In general, the counts of the Gyoza samples were lower than those of the salad samples. In the samples of salad, yeasts were found to be the second largest microbial group, and the predominant species were Candida (C. intermedia, C. lipolytica, C. parapsilosis, C. sake, etc.), Rhodotorula (R. glutinis, R. minuta, R. rubra), Trichosporon (Tr. cutaneum, Tr. pullulans) and Cryptococcus (Cr. albidus, Cr. infirmo-miniatus, Cr. laurentii). Yeast flora in the samples of Gyoza included Candida, Rhodotorula, Debaryomyces, etc. In the two kinds of samples tested, the main bacterial genera were Pseudomonas, Klebsiella, Lactobacillus, Bacillus, Staphylococcus, etc., and representative fungal genera were Penicillium, Phoma, Cladosporium, etc. Psychrotrophic organisms grown within 2 weeks at 5°C accounted for 92.9% of the total yeast cultures and 47.1% of the total fungal cultures isolated from all the samples tested. The obligately psychrotrophic yeasts from the chilled salad were Cr. infirmo-miniatus and Trichosporon spp.
Microbiological examination of chilled roe of sea urchin (Namauni; Heriocidaris spp., etc., 20 samples), sliced raw tuna (Maguro sashimi; Thunnus spp., etc., 20 samples) and the foot of the hen clam (Bakagai sashimi; Mactra spp., 17 samples) was carried out to examine the microflora, especially the yeasts. The samples were collected from retail markets by official food examiners and investigated by the official microbiological methods. Counts of bacteria, yeasts and fungi in the samples of roe of sea urchin ranged from 103 to 107, 102 to 107 and below 104 per gram, respectively. Counts of bacteria, yeasts and fungi in the samples of sliced raw tuna and the foot of the hen clam were found to range from 103 to 106, 101 to 104 and 104 per gram, respectively. In the three kinds of seafood samples, yeasts were found to be the second largest microbial group and the predominant species were asporogenous yeasts such as Rhodotorula (R. glutinis, R. rubra, R. pallida), Candida (C. guilliermondii, C. humicola, C. lipolytica, C. parapsilosis, C. zeylanoides), Trichosporon (Tr. cutaneum, Tr. pullulans, Tr. variabile) and Cryptococcus (Cr. albidus, Cr. infirmo-miniatus, Cr. laurentii, Cr. macerans). Trichosporon cutaneum, a species of opportunistic pathogen, was isolated from 45% of the samples of sliced raw tuna. In all the samples tested, the main bacterial genera were Pseudomonas, Corynebacterium, Micrococcus, Staphylococcus, etc., and representative fungal genera were Penicillium, Phoma, Fusarium, Mucor, etc. Psychrotrophic organisms grown within 2 weeks at 5°C accounted for 94.6% of the total yeast cultures and 55.0% of the total fungal cultures isolated from the seafood samples.
A method is described for the rapid detection of 11 water-soluble natural dyes in foods. A sample solution, prepared by aqueous extraction of foods, was shaken with ether to separate oil-soluble material. The solution was adjusted to pH 4-5. Polyamide powder (0.5g) was added to the solution, and the mixture was stirred for 15min. After filtration and washing with water, the dyes were eluted with 0.05% HCl in methanol. The dyes were identified by thin-layer chromatography and visible spectrophotometry. Since riboflavin was not adsorbed on polyamide, kaolin was used in this case. In the presence of organic acids, the extents of adsorption of safflower yellow, betanin, monascus pigments and riboflavin were reduced. In addition, sugar interfered with the adsorption of crocin blue, betanin and riboflavin. This method was applied for the detection of water-soluble natural dyes in candies, soft drinks and other foods.
An analytical procedure was developed for the qualitative and quantitative determination of total bromide residues in agricultural products, using a detector tube. A 20g sample was added to 25ml of alkaline monoethanolamine solution and ashed. The ashed residue was dissolved in 0.1N NaOH and filtered into a flask. Next, 0.5g potassium permanganate and 5ml of phosphoric acid were added, and the analysis apparatus (Fig. 1), including a detector tube, was assembled. After bubbling air (flow rate, 80ml/min) through the sample solution for at least 3 hours, the detector tube was removed from the apparatus and the length of the color change in the tube was measured. (The bromine reacted nearly quantitatively with fluorescein to produce tetrabromofluorescein, and the color changed from yellow to reddish-pink.) The recoveries of bromide added to rice, wheat, chestnut and cherry were more than 97%, and the detection limit was 1ppm. The present method was found to be satisfactory for the qualitative and quantitative determination of total bromide in agricultural products.
The effects of potassium metabisulfite on some dehydrogenases in isolated viable rat hepatocytes were compared with those on the enzymes in broken cells and on the purified enzymes. The activities of purified lactate and malate dehydrogenase were strongly inhibited by 10-3M metabisulfite, but no inhibition was observed with glucose-6-phosphate dehydrogenase or isocitrate dehydrogenase. However, metabisulfite did not inhibit the lactate dehydrogenase in viable hepatocytes when the cells were preincubated with 10-3M metabisulfite for 5, 10 or 20min, and in fact was found to be stimulatory. On the other hand, the stimulation of the enzyme was not observed in broken cells; some inhibition was seen under these conditions. There was no significant difference between viable and broken cells in terms of the remaining activity of sulfite oxidase on incubation with metabisulfite.