To identify the volatile compounds present in unusual-smelling raw beef, the headspace constituents of simmering beef were examined. The procedure was as follows. The sample was heated with distilled water, and all volatile compounds were removed by constantly flushing the surface of the slurry with nitrogen gas, then trapping the volatiles in a series of reagent traps. For carbonyl compounds, absorption traps containing 2, 4-dinitrophenylhydrazine solution were used. For sulfur compounds, lead acetate solutions were used. The volatiles were then bubbled through sodium hydroxide solution, and through a tube containing anhydrous calcium chloride in sequence. After passing through these traps, the nitrogen stream, together with the headspace vapors, was led into a trap cooled with acetone and solid carbon dioxide. The contents of the final trap were analyzed by gas-liquid chromatography and GC-mass spectrometry. One volatile compound which contributed to the unusual smell was identified as p-dichlorobenzene (p-DCB). 1, 3, 5-trichlorobenzene was used as an internal standard for gas-chromatographic determination. p-DCB was present in unusual-smelling beef in the range of 4.4-55.9ppm in the muscle, 165ppm in the perirenal fat, 11.3ppm in the pancreas, 1.9ppm in the lung, 3.4ppm in the liver and 2.8ppm in the spleen, while the amounts in normal beef were 0.1ppm in the perirenal fat and n. d. /trace in the muscle.
Nitrate in foods is important because of its role in the detinning of cans containing canned foods and in connection with the formation of nitrosoamines in processed foods. In this paper, convenient colorimetric and gas-chromatographic methods for the determination of nitrate in foods are presented. An aliquot of the test solution is mixed with sulfuric acid (3+1) and with an alcoholic solution of 2, 6-xylenol, and the mixture is left to stand for 25 minutes at 37°C. Nitration of 2, 6-xylenol occurs, and the nitroxylenol extract in chloroform can be used for colorimetry, after reextraction with M/5 borate buffer, or for FID-gas chromatography. It was found that 1) the absorption maximum of nitroxylenol in the buffer solution is 432nm, 2) the partition coefficent of nitroxylenol with borate buffer and chloroform depends on the pH of the buffer. Taking advantage of this, the pH of the extracting solution can be varied in accordance with the amount of nitrate in the test solution; pH 8.0 is suitable for less than 200μg per tube, pH 8.5 for less than 100μg and pH 9.0 for less than 30μg. It was shown that these methods are not interfered with by nitrite.
The chemical form of nickel in tea taken as a beverage was investigated in order to evaluate its toxicological and physiological effects. 1) About 89% of the nickel in tea leaves (Sencha) was extracted by boiling water. No nickel was detected in bound or complexed form in extracts from the tea with organic solvents such as n-hexane, benzene, chloroform and ethylacetate. 2) Sephadex G-25 gel filtration of the water-soluble nickel indicated that it forms complexes with ninhydrin- or phenol- sulfuric acid-reactive substances; however, nickel does not bind to proteins or pigments in tea, and is not present as unbound Ni. 3) Thin-layer chromatographic analyses demonstrated the presence of six distinct Ni complexes in the water-soluble nickel fraction obtained by gel filtration. A major constituent was positive to ninhydrin and to phenol-sulfuric acid staining.
Seven outbreaks of Bacillus cereus food poisoning occurred in Osaka prefecture during the period from June 1973 to October 1978. All the outbreaks involved cookedorice, from which large numbers of B. cereus were isolated. Six outbreaks were of “Vomiting type” with the characteristics symptoms of nausea and vomiting and an incubation period of between 0.5 and 4hr; the other one was of “Diarrheal type” with diarrhea and abdominal pain and an incubation period of 2 to 12hr. Eighty-two samples of uncooked rice, 142 samples of cooked rice and 41 samples of “Sushi” were purchased from retail shops and caterers and examined for B. cereus; 66% of the uncooked rice, 66% of the cooked rice and 42% of the “Sushi” were found to be contaminated with B. cereus. All 36 strains isolated from rice involved in the food poisoning failed to hydrolyze starch, whereas 38% of the strains isolated from cooked rice and 83% of those from uncooked rice did hydrolyze starch. All the strains isolated from the outbreaks survived heat treatment at 90°C for 60min, at 100°C for 10 and 30min or at 105°C for 5min. Of the strains isolated from cooked rice, 97%, 70%, 39%, and 33% survived heating for 60min at 90°C, for 10min at 100°C, for 30min at 100°C, and for 5min at 105°C, respectively; of those isolated from uncooked rice, 93%, 26%, 10% and 5% survived heating for 60min at 90°C, for 10min at 100°C, for 30min at 100°C, and for 5min at 105°C, respectively.
“Fugu” imported from Formosa into Fukuoka Airport in 1977 were divided to species, and the flesh was examined for toxicity by mouse bioassay. The results are summarized below. 1) Out of 6 specimens of Lagocephalus lunaris lunaris caught in the South China Sea, 5 were found to be toxic. The values of toxicity of the specimens ranged up to 171.2MU/g, and were estimated to be 39.3MU/g on average. 2) One specimen each of Lagocephalus laevigatus inermis and Lagocephalus lunaris spadiceus caught in the South China Sea were both toxic, giving values as high as 21.5 and 11.8MU/g, respectively. However, all 11 specimens of Lagocephalus lunaris spadiceus caught in the East China Sea and to the north of this area were non-toxic. 3) Both Lagocephalus lunaris lunaris and Lagocephalus lunaris spadiceus showed osteophyma-like swelling of the caudal vertebrae and postclaviculla. Thus, they could not be distinguished in terms of the swelling. 4) The specimens of Lagocephalus lunaris spadiceus were divided into two broad classes based on the color of the backs; one was grayish olive, and the other was dark blue or dark green. The colors may be related to the geographical source of the fish.
Unpasteurized liquid whole eggs were stored at 10°C and 5°C to investigate their preservability from bacteriological and chemical viewpoints. After 4-5 days at 10°C or 8 days at 5°C, little deterioration of quality was observed. However after 6 days at 10°C or 10 days at 5°C, we observed the formation of off-odor (fishy or fruity), an increase in bacterial counts, a decrease in pH, a decrease in glucose content, an increase in volatile basic nitrogen (VB-N), formation of trimethylamine nitrogen (TMA-N), and an increase in the acidity of the ether extract. In these storage tests, it was found that psychrotrophic bacteria such as Aeromonas, Pseudomonas, Flavobacterium, and Micrococcus became predominant and that coliform bacteria and enterococci grew only slowly. On the other hand, on storage at 25°C, Enterobacteriaceae, Micrococcus, and Streptococcus dominated, and fairly rapid growth of coliform bacteria and enterococci was observed. The strong putrid odor formed after 2 days at 25°C was different from the fishy or fruity odor that developed at 5°C or 10°C. In liquid whole eggs stored at 5°C or 10°C, most of the isolates forming red colonies on desoxycholate agar were not coliform.
Dithiocarbamate fungicide residues in agricultural products were determined by measuring the decomposition products. Dithiocarbamate fungicides were divided into two groups, ziram type (dimethyldithiocarbamate) and zineb type (ethylene-bis-dithiocarbamate). The ziram type was extracted with chloroform and measured as dimethylamine after acid hydrolysis. The dimethylamine was quantitated by gas chromatography of its benzenesulfonyl derivative using a flame photometric detecting system (FPD). The zineb type was measured as ethylenediamine after hydrolysis with acidic stannous chloride. The ethylenediamine was quantitated by FPD gas chromatography of its methanesulfonyl derivative. The recovery of ziram added to crops was in the range of 64 to 93%. That of zineb added to crops was in the range of 67 to 91%. Three samples were found to contain 1.8-4.8ppm of ethylene-bis-dithiocarbamate.
The remaining flavor in chewing gum cud was measured by gas chromatography. The chewing gum cud was dissolved in tetrahydrofuran with diphenyl as an internal standard, and the amounts of d-carvone (for the spearmint flavor) or l-menthol (for the peppermint flavor) were determined. The release of flavors in all tested samples after chewing for 10 minutes was less than 30% of the initial amount. The rate of release of flavor from each stick of gum (3g) was in the range of 0.52-0.87mg/min during 0-5min, and 0.08-0.17mg/min during 30-60min. The release rate of spearmint flavor was rather faster than that of peppermint flavor.
The Vital Red (VR) method (column chromatography) for the analysis of polyvinylpyrrolidone (PVP) in beer was improved by the use of a new separable mini-column and a modified packing method. A simplified method also as developed by which PVP in the range of 1-10ppm was semi-determinable visually with the naked eye. Congo Red, which is readily available in Japan, was tested to determine whether or not it could be used in the new method. It gave the same sensitivity as the VR method, but the recovery of PVP from beer was a little over 100%. Using these methods, no PVP was detected in 4 kinds of Japanese beer and 8 kinds of imported beer. GPC high performance liquid chromatography was also studied for PVP determination, but without success.
A method was developed for determination of ethylenethiourea in agricultural products by gas liquid chromatography using a flame photometric detector. The analytical method consists of five procedures: extraction with methanol, conversion to the S-benzyl derivative, clean-up by washing with chloroform, N-methanesulfonylation under basic conditions, and measurement by GLC. The resulting derivative (2-benzylthio-1-methanesulfonyl-2-imidazoline) was stable for five weeks at room temperature and was detectable at a level of 0.01ppm in agricultural products without interfering GLC peaks. The recoveries of ethylenethiourea from fourteen agricultural products fortified at a level 0.1ppm averaged 81%.