A simple and sensitive HPLC method is described for quantitative determination of some synthetic antibacterials in animal tissues. The compounds are divided into two groups, A and B. Tissue samples are extracted with acetonitrile and then group A is purified on a silicagel cartridge and group B by hexane partition; no other clean-up procedure is needed. Recoveries of the antibacterials spiked in animal tissue were 64-99%. The detection limits of quantitative determination by the proposed method were 0.01ppm for each antibacterial. The calibration curves for these compounds showed good linearity in the ranges of 0.5-50ng for carbadox, 1-100ng for thiamphenicol and furazolidone and 2-200ng for other drugs. Many chicken samples (total 121) which were purchased from a poultry processing plant in Tokyo were analyzed by the proposed method. Decoquinate was detected in two samples of chicken muscle at levels of 0.02 and 0.03ppm.

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As the treatment of soybean sprouts and cabbage leaves with sodium hypochlorite (NaClO) generated various amounts of chloroform (CHCl₃), we conducted experiments to investigate the substances in these vegetables which were involved in CHCl₃ formation.
When filtrates of soybean sprouts and cabbage leaves extracted with water and their residues were reacted with NaClO, a linear relation was observed between the UV absorbance (265nm) of the filtrates and the amount of CHCl₃ formation. The amount of CHCl₃ formation in the residues was relatively small, suggesting that the substances involved in CHCl₃ formation were mainly present in the vegetable filtrates. Filtrates of soybean sprouts and cabbage leaves were subjected to gel filtration, and four fractions were obtained in each case. Each fraction was reacted with NaClO to investigate the absorbance and level of total organic carbon (TOC). There was a correlation between the amount of CHCl₃ formation and the absorbance and TOC, and a particularly high rate of CHCl₃ formation was noted in the second fraction of soybean sprouts, indicating that the difference in CHCl₃ formation in the vegetable filtrates is due to the difference in the components of the vegetables fractionated by gel filtration.

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Allyl isothiocyanate, a main flavoring constituent of wasabi and mustard, is known to have strong antimicrobial activity. A study was made of the vapor pressure changes and the stability under various conditions of this substance as part of a research program aimed at producing a preparation which would allow exploitation of its antibacterial effect for industrial purposes.
It was found that the vapor pressures of allyl isothiocyanate at relative humidities of 0 and 80% were almost the same, and that vapor pressure could be controlled through dilution with non-volatile oils such as ODO (MCT: medium chain triglyceride).
The investigation of stability revealed that, after one year's storage at room temperature, the residual level of allyl isothiocyanate was more than 90%. Further improvement of its stability was observed when the head space gas was replaced with nitrogen. In the presence of ethanol, allyl isothiocyanate produced an additional compound, and for this reason it was considered that the development of a preparation based on a mixture of these two substances would be impractical. Heat treatment caused allyl isothiocyanate to decompose rapidly at temperatures between 170 and 180°C, indicating that processing at temperatures of this level and above might not be feasible.

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A procedure for determination of 20 organophosphorus, 19 carbamate and 5 pyrethroid pesticides in raw coffee beans by gas chromatography was developed. Extract of coffee beans was directly analyzed for organophosphorus and pyrethroid pesticides, and purified by silica gel column chromatography before GC analysis for carbamate pesticides. No residual pesticide was detected, but much bromine was detected in 11 samples imported from 10 countries. The detection limit was 0.001ppm for organophosphorus pesticides, 0.01ppm for carbamate and pyrethroid pesticides by the proposed method, and 0.05ppm for bromide.

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We evaluated an assay method of proteolytic activity applicable to both commercially available microbial protease and papain, which are used as enzyme preparations for food in Japan.
The optimal pH values for the reaction with casein as a substrate for 10 minutes were 3, 6, or 8 for fungal protease, 7, 8, or 10 for bacterial protease, and 7 or 8 for papain. Therefore, 0.6% casein solution at the optimal pH for each enzyme was used as the substrate. The appropriate reaction temperature was 37°C for each enzyme. As a diluent, 0.01M sodium chloride solution containing 0.002M calcium acetate and 0.002M calcium sulfate prevented decreases in enzyme activity. As a reagent for protein precipitation, 0.11M trichloroacetic acid containing 0.22M sodium acetate and 0.33M acetic acid was appropriate for all the enzyme sample preparations.
The enzyme activities of 35 microbial proteases from 13 companies measured by this method were in the range of 200-1, 132, 100U/g, and those of 3 papain preparations from 3 companies were in the range of 13, 500-167, 400U/g.

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A method for the quantitative determination of trace amounts of tetramethylsuccinonitrile (TMSN) released into foods from their plastic containers is described. TMSN is a decomposition product of 2, 2′-azobisisobutyronitrile used as a polymerization initiator for monomers in plastic production. TMSN in 50g (or ml) of food is steam-distilled. The distillate, to which nitrobenzene has been added as an internal standard, is shaken with 50, 30 and 30ml of methylene chloride for extraction of TMSN. The combined solvent layers are concentrated to 5-7ml by a rotary evaporator, and to 1ml with a nitrogen gas stream. The concentrate is washed 3 times with 1ml of 6N hydrochloric acid. The solvent layer is dried with 1g of anhydrous sodium sulfate. The final step consists of gas chromatography using a 180cm column of 5% Thermon 1000 and 0.5% phosphoric acid on Chromosorb W and a nitrogen-phosphorus detector. The limit of detection was 1μg/kg or μg/L. Recoveries of TMSN ranged from 94.0 to 104.2% at levels of 10-20μg/kg. The method was applied to 9 kinds of foods packed or bottled in containers made of plastics. No interfering substances were observed on the gas chromatograms.

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A method for simultaneous determination of 16 kinds of organochlorine and pyrethroid pesticides in agricultural products by capillary GC with ECD detection was studied, and satisfactory operating conditions were identified. We have improved the official method for sample preparation by connecting Sep-Pak Florisil with Sep-Pak Alumina A to remove interfering substances, allowing the analysis time to be reduced.
The recoveries of organochlorine and pyrethroid pesticides added to 8 kinds of agricultural products were in the range of 47.7-103%. In surveillance for residual pesticides in 13 kinds of imported agricultural products, none of them was detected.

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[in Japanese]

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