The ability of Listeria monocytogenes to survive or grow during Camembert cheese manufacturing, ripening and storage was examined. Two experimental methods were applied for manufacturing Camembert cheese: using Listeria-contaminated milk (1.6×104cells/ml), and using Listeria-contaminated brine (1.5×106cells/ml). Listeria counts decreased in both cases during the beginning of the ripening process; in the later stage an increase of the count occurred. The count of this organism after ripening was about the same as in the initial stage. After that the number increased gradually, and Listeria counts of 1.7×105cells/g and 1.5×108cells/g were attained after 50 days, respectively. Listeria monocytogenes survived in 18% brine at 12°C for more than 21 days.
The factors affecting formation of hydrogen peroxide (H2O2) in coffee have been studied. H2O2 in coffee was identified by TLC and determined by using an oxygen electrode method and modified 4-aminoantipyrine colorimetry. H2O2 was not detected in green coffee beans, but was detected in coffee infusion. Coffee infusion or coffee solution prepared using a coffee maker contained less H2O2 than those prepared using a filfer or a beaker. The greater the degree of roasting, the greater was the formation of H2O2 in coffee beans. The formation of H2O2 was also influenced by temperature and light. Some components of coffee beans, saccharose, chlorogenic acid, glycine, caffeine, caffeic acid and quinic acid, did not contain H2O2, but when these components were roasted in the same manner as coffee beans and an infusion was prepared, H2O2 was formed. Formation of H2O2 from roasted caffeic acid was particularly marked.
In order to differentiate between Lagocephalus wheeleri, L. gloveri and L. lunaris, their skin extracts were separated by HPLC/on an Inertsil 5 ODS column (4.6mm i. d.×50cm) using a mobile phase of MeOH-acetonitrile-tetrahydrofuran-H2O (50:35:5:10) at a flow rate of 1.8ml/min, with detection at 445nm. Pigments in skin were extracted with MeOH-CH3COOH (50:1) at 70-80°, and the extract was concentrated, saponified with KOH in EtOH and further extracted with diethyl ether. This extract was washed with distilled water and concentrated. The concentrate was dissolved in the mobile phase. Four main peaks were chosen from among the separated peaks. The three species of pufferfish could be distinguished by the ratio of these peaks. Identification by the present method was possible on boiled skin as well as fresh skin of the three species of pufferfish.
Thirty-one specimens of “hoshifugu” pufferfish, Arothron firmamentum, consisting of 16 males and 15 females were obtained from the coastal seas off Oita and Yamaguchi in the fall of 1990. Muscle, skin, liver, gonad and digestive tract were examined for toxicity by means of the mouse assay method. The toxicity of the skin was at rather weak level and was higher in females than males: the frequency (%) of toxic specimens was 12.5% in males and 33.3% in females, and the maximum lethal potency was 30.6MU/g in males and 43.6MU/g in females. The ovary was more toxic: the frequency (%) of toxic specimens was 80.0% and the maximum lethal potency was 888MU/g. The toxicity of the digestive tract was at weak level, while that of the muscle, liver, and testis was lower than 10MU/g. The “hoshifugu” pufferfish has been characterized as having equivocal toxicity, but the above results indicate that this species should be re-classified as toxic.
On the basis of the total diet-market basket method, about one hundred kinds of food were respectively purchased in 1977, 1985 and 1990 in Osaka, Japan, and they were cooked, divided into 13 groups and frozen at -40°C. Dietary intakes of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinaed dibenzofurans (PCDFs) and coplanar PCBs (Co-PCBs) through food in Japan were studied by using these 39 samples. The total dietary intake of PCDDs and PCDFs was 175pg TEQ (2, 3, 7, 8-Tetrachlorinated dibenzo-p-dioxin Toxic Equivalent), i. e., 40pg TEQ/day of PCDDs and 135pg TEQ/day of PCDFs. Co-PCBs, having the same toxic effect as PCDDs and PCDFs, gave an estimated intake of 660pg TEQ/day, which was calculated by using the 2, 3, 7, 8-T4CDD toxicity equivalency factors reported by Hanberg et al. In addition, it was found that Japanese took about 60% of the TEQ of the three chemicals in food through fish & shellifish, daily intakes of which are larger in Japan than in Europe or the USA. It is noteworthy that the dietary intake of Co-PCBs as TEQ was much greater than that of PCDDs or PCDFs.
The antioxidative effect of ascorbyl stearate (AS) and its synergistic effect with α-tocopherol (α-Toc) in the case of air oxidation of purified trilinolein (TL) and triolein (TO) were examined, and free ascorbic acid (AA) was used for comparison. Samples were oxidized by introducing oxygen at 75°C into a dark glass tube, then oxidized samples were taken at various times and their peroxide values (POV) were measured. The time required for POV to reach 500 (meq/kg) was regarded as the induction period. The following results were obtained. (1) When 0.01-2.0mM/kg of AS was added to TL or TO, and the oxidation test was carried out, no antioxidative effect was observed. (2) TL containing 1.0mM/kg of α-Toc was supplemented with 0.01-2.0mM/kg of AS and subjected to the oxidation test. A synergistic effect of AS was clearly observed; the induction period was prolonged 2.5-3 times compared with α-Toc alone. A similar effect was observed with TO containing 0.1mM/kg of α-Toc, when 0.01-0.3mM/kg of AS was added. (3) An optimum concentration of AS was observed as a synergist with α-Toc; higher levels of As did not increase the effect any further. The effect of AS resembled that of AA.
The comparative uptakes of metals by cultured roots and the roots of the corresponding mother plant were studied to estimate the transference of metals to food additives produced by means of tissue-culture techniques. The normal cultured roots of Rubia tinctorum and Glycyrrhiza glabra were induced in Murashige and Skoog (MS) medium containing phytohormones (indole-3-acetic acid and kinetin). The concentrations of various metals (Ca, Mg, Fe, Mn, Zn, Mo, Cu) in the normal cultured roots of R. tinctorum and G. glabra, the hairy roots of R. tinctorum and the roots of both mother plants were determined by ICP-AES. The concentrations of Mn, Zn, Mo in the cultured roots were one order of magnitude higher than those in the roots of the mother plants. The uptake ratio of Cu from the medium was the highest and those of Zn and Mo were also high among the metals in MS medium. On the other hand, the mother plants exhibited the greatest uptake of Ca from the soil, while the uptake of Fe was significantly low.
The mutagenicity of the ether extract from sun-dried and broiled saurel (Trachurus japonicus) was examined in S. typhimurium TA 100. The level of lipid peroxidation of the fish was also assayed. Sun-drying and broiling promoted lipid peroxidation and increased the mutagenic activity. Although the mutagenic activity (without S9) was not seen in the ether extract from raw fish, it was produced and increased during the processes of sun-drying and broiling. The ether extract from sun-dried (12hr) and broiled saurel induced 409 revertants/20mg. After fractionation through a Sep-Pak silica cartridge, the ethylacetate (AcOEt) fraction showed the highest mutagenic activity. The activity was decreased by the addition of sodium sulfite in a dose-dependent manner, and the presence of carbonyl compounds including methylglyoxal (MG) was demonstrated. The MG content found by HPLC was 6.16μg in the AcOEt fraction from 20mg of ether extract. MG appears to be formed through the process of peroxidation of fish lipid during sun-drying and broiling.
Soluble chlorides, sulfates, bromides and iodides in food coal-tar dyes can be determined by suppressed ion chromatography with a conductivity monitor. Each food coal-tar dye was dissolved in water and ion-chromatographed directly with eluent containing 20% acetonitrile, 2mM TBAOH (tetrabutylammonium hydroxide) and 0.8mM sodium carbonate. IonPac NG1 was used as the guard column, and IonPac NS1 as the separating column. These columns are made from neutral polystyrene resin. The dyes are adsorbed on the guard column in the eluent containing the ion-pair reagent TBAOH, but four anions are separated by the separating column. After separation of the four anions, the columns were switched and the dyes were eluted from the guard column with 50% acetonitrile. The recoveries of sodium chloride, sodium sulfate, sodium bromide and sodium iodide (each 10μg/ml) added to 1000μg/ml dye solution were in the range of 89.6-106.9%. The determination limits were 0.1μg/ml (NaCl), 0.2μg/ml (Na2SO4), 0.2μg/ml (NaBr) and 0.5μg/ml (NaI). Thirty-one commercial samples were analyzed. Chlorides (as sodium chloride) and sulfates (as sodium sulfate) of all samples were within the limits of specifications. The commercial Food Red No. 104 contained 0.86-1.16% bromides as sodium bromide. The commercial Food Red No. 3 and the commercial Food Red No. 105 contained 0.07-0.22% iodides as sodium iodide.
The alkaline unwinding method to measure DNA damage was reported by Morris and Sherzer (Environ. Mutagen., 7, 871, 1985). In this study, the various assay conditions of the method were examined to improve the detection sensitivity. The detection sensitivity to hepatic DNA damage induced by N-nitrosodimethylamine (NDMA) increased 2-fold when the assay temperature was increased from 4°C to 10°C or 20°C. Changes of liver homogenate concentration (6-10%) markedly influenced the detection sensitivity when the assay was conducted at 4°C, but not at 10°C or 20°C. In liver from mice administered trichloroethylene, no significant DNA damage was detected by the orignal method. In contrast, significant DNA damage was detected when the unwinding assay was conducted using a 6% liver homogenate at 20°C. The modified condition seems to be suitable for detecting stimulants which induce weak DNA damage.
An ion chromatographic method was developed for the determination of ferrocyanide in wine. Hydrogen cyanide, which was produced from ferrocyanide by heating and addition of 10% sulfuric acid (3ml) to wine (30ml), was entrained by nitogen gas into a trapping solution containing 0.1N sodium hydroxide. A modified Rankine apparatus was used. Then the trapped solution was directly subjected to ion chromatography with electrochemical detection. The cyanide ion derived from ferrocyanide was separated under basic solvent conditions (4mM ethylenediamine, 20mM sodium bicarbonate and 100mM sodium hydroxide) on a column of Tosoh DEAE-5PW Glass at a flow rate of 1.2ml/min at 40°C. It was detected by a Tosoh EC-8000 detector with a silver working electrode at 0mV (determination limit: 0.5ppb as cyanide anion). The recoveries of various amounts of ferrocyanide (50-1, 000ng/ml calculated as Na4Fe(CN)6 in wine) added to white and red wine were 88-130%. The presence of additional Na2SO3 (688μg/ml wine) did not interfere with the measurement of the recoveries. The described method is very sensitive (determination limit: 1ng/ml calculated as Na4Fe(CN)6 in wine), so that the background level of cyanide (less than 5ppb as cyanide anion in the trapped solution) could be observed in various kinds of wine bottled in Japan. Since a trace of cyanide was also detected in musts for wines, it is likely that the cyanide in wine is naturally occurring.
Soy-milk was prepared from 100g of soybeans by boiling, filtration and further heating, after the beans had been soaked overnight in 900ml of distilled water containing 2.03g of cadmium chloride. The supernatant was separated from the lipid layer and residues by ultracentrifugation. Most of the cadmium added was found in the okara fraction (residues from the filtration step), and several percent of the added cadmium bound to some components in the soy-milk. Separation of the supernatant by gel filtration on Sephadex G-50 revealed that ligand-binding cadmium was localized in two molecular weight fractions (about 10, 000 and about 1, 000). Approximately 80% of the ligand-binding cadmium in the supernatant was found in the low-molecular-weight fraction. After in vitro peptic/pancreatic digestion, a decrease in the amount of the high-molecular-weight ligand-binding cadmium was observed, with an increase in the amount of the low-molecular-weight ligand-binding cadmium.