The determination of residual vinylidene chloride monomer (VDCM) in polyvinylidene Chloride (PVDC) food packaging films was studied. PVDC packaging films were dissolved in 20ml of tetrahydrofuran (THF). VDCM and THF were vaporized by heating in a water bath at 80°C, and collected in a test tube of THF (2.5ml) cooled with ice under a nitrogen gas flow of 40-80ml/min until 10ml had been obtained. The concentration of VDCM in the cooled test tube was determined by mass fragmentography, using selected ion recording at m/e 61. The recovery of VDCM added to PVDC household wrap film was found to be 77.2-83.9% in the range of 1.0 to 10.0μg, and the coefficiant of variation was found to be 3.2%. No VDCM could be detected in commercial PVDC food packaging films such as household wrap, fish sausage wrapping and processed cheese wrapping.
The determination of residual acrylonitrile (AN) in acrylonitrile styrene copolymers (AS) and acrylonitrile butadiene styrene copolymers (ABS) was studied. AS and ABS were dissolved in 20ml of dimethylformamide (DMF). AN and DMF were vaporized by heating on a mantle heater so as to give a distillation rate of about 1.5ml/min. They were collected in a test tube of DMF (4ml) containing 100μg of benzene (internal standard) under a nitrogen gas flow of 60-80ml/min until 10ml had been obtained. The concentration of AN in the test tube was determined by mass fragmentography, using selected ion recording at m/e 52, together with the internal standard. The recoveries of AN from AS and ABS in the range of 10.0 to 20.0μg were 92-103% and 95-103%, respectively. The coefficient of variation did not exceed 2%. Commercial AS and ABS were analyzed and found to contain 4-110 ppm AN.
The toxic effect of 13 food dyes were studied in Artemia salina. It was found that xanthene dyes containing halogen atoms were more toxic than other types of food dyes. Phloxin and Rose Bengal (containing chlorine) were particularly toxic. The effect of food dyes on leucine aminopeptidase and lactate dehydrogenase activity in A. salina were studied. Leucine aminopeptidase activity was not greatly inhibited by these dyes. The inhibitory effects of food dyes on leucine aminopeptidase were not consistent with their toxic effects on A. salina. Leucine aminopeptidase activity in P. caudatum was inhibited by these dyes, as reported previously, and kinetic experiments suggested that the properties of leucine aminopeptidase from A. salina are different from those of the P. caudatum enzyme. On the other hand, the inhibitory effects of food dyes on lactate dehydrogenase in vitro were consistent with the toxic effects of the dyes on A. salina. The effects of food dyes on lactate dehydrogenase activity were also studied in vivo, and the mechanism of the toxicity is discussed in relation to the anaerobic metabolism in A. salina. The mortality rate of A. salina and the inhibitory effects on enzyme activity in crude extracts of A. salina may provide to be useful indices for determination of the toxic effects of such dyes.
The effects of various food extracts (from animal meat, fish meat, vegetables and seaweed) on spore germination of strains of heat-resistant and heat-sensitive Cl. perfringens type A were compared. The germination of spores was estimated by observing the decrease in absorbancy (O.D. at 580nm) of spore suspensions and confirmed by observation with a phase-contrast microscope. The following results were obtained. 1) Heat-shocked spores (80°C, 10min) of heat-resistans strains germinated rapidly and completely in all of the food extracts examined, while little germination occurred with the same spores without heating. 2) Both heated and unheated spores of heat-sensitive strains germinated well in food extracts, except in two kinds of vegetable extract, although the extent of germination was generally greater in the latter than in the former. 3) It appeared that the germination of spores of heat-resistant strains was caused by the presence of K+ in the extracts (so-called “ionic germination”), whereas the germination of spores of heat-sensitive strains was induced by a combination of inorganic ions and organic germinants (so-called “physiological germination”).
In order to identify the source of bacterial contamination in unpasteurized liquid whole egg products, the contents of intact eggs stored under various conditions were examined bacteriologically. Of 1120 egg samples chilled at 2-3°C for about 1.5 months, 61 (5.5%) showed bacterial contamination of more than 102 cells per gram. However, only 4 showed bacterial counts of more than 106 per gram, and these were mainly due to the presence of gram-negative bacteria. Washing of intact eggs before storage increased the frequency of bacterial contamination in the contents of the eggs. A liquid whole egg sample inoculated with bacterial flora present on the egg shell showed only a relatively small increase in the bacterial count within 1 hour at 19°C. Studies on liquid whole egg products obtained from two factories having different manufacturing capacities and quality control methods suggested that high quality products may be obtained by using fresh and flawless intact eggs, washing the eggs adequately before breaking, and maintaining strict standards of hygiene during the manufacturing process.
An analytical procedure was developed for the quantitative determination of residues of the fumigant methyl bromide in agricultural products by means of gas chromatography. Methyl bromide was extracted with ethanol and transferred into a flask. It could be collected in ethanol in an absorption tube kept at -70° with acetone-dry ice by bubbling air (flow rate, 80ml/min; bubbling time, 120min) through the sample solution. Methyl bromide was then determined by gas chromatography using a hydrogen flame ionization detector. The recoveries of methyl bromide added to wheat, unpolished rice, chestnut, cherry and plum were more than 89%, and the detection limit was 0.05ppm. No methyl bromide was detected in a survey of commercial agricultural products by this procedure. The present method was found to be satisfactory for the quantitative determination of methyl bromide in agricultural products.
Four hundred and twenty-three strains of motile enterococci and 210 strains of nonmotile ones were collected from stream waters and butterflies in mountain areas, from pollutted waters in urban areas, and from human and swine feces. These strains were identified as Streptococcus faecalis, S. faecalis subsp. liquefaciens and S. faecium. The organisms identified as S. faecium formed a fairly heterogenous group, while S. faecalis and S. faecalis subsp. liquefaciens organisms were remarkably homogenous as regards their physiological properties. It is proposed that the S. faecium organisms should be divided into 5 biotypes: the typical S. faecium organisms were classified as Biotype 1; S. durans as Biotype 2; yellow pigmented non-motile enterococci as Biotype 3; non-pigmented motile enterococci as Biotype 4; yellow pigmented motile enterococci as Biotype 5. Biotype 2 differed from Biotype 1 in its inability to ferment mannitol and arabinose, and in having no requirement for riboflavin; Biotype 3 differed in having yellow pigmentation, in the failure of most strains to grow at 47°C and in the ability to ferment xylose; Biotype 4 differed in motility, tetrazolium-reducing ability, the ability to ferment xylose and α-methyl-D-glucoside, failure to grow at pH 4.65 and to decarboxylate tyrosine, and in having no requirement for isoleucine, threonine, glycine or riboflavin; Biotype 5 differed in motility, yellow pigmentation, failure to grow at 47°C or at pH 5.0, final pH higher than 4.1, tetrazolium-reducing ability, the ability to ferment xylose, α-methyl-D-glucoside and inulin, inability to decarboxylate tyrosine, and in having no requirement for isoleucine, threonine, tryptophan, glycine or riboflavin. The yellow pigmented motile enterococci, Biotype 5, were isolated from 21 of 103 samples of human feces, 8 of 10 samples of polluted waters, 21 of 30 samples of the mountain stream waters and 7 of 38 butterfly samples. Although non-pigmented motile enterococci, Biotype 4, were recovered from 15 of 103 samples of human feces, 3 of 16 samples of swine feces, and 1 of 10 samples of polluted waters, none was found in the mountain stream or butterfiy samples. Biotype 5 and S. faecalis subsp. liquefaciens organisms apear to be the most common enterococus flora in the environment.
The aldehydes formed by reaction between amino acids and hydrogen peroxide were investigated. 2, 4-Dinitrophenylhydrazones of the reaction products of glycine, alanine, valine, leucine, isoleucine, and phenylalanine with hydrogen peroxide all gave single spots on thin layer chromatograms. Comparison of the Rf values, UV absorption maxima, melting points and colors of the 2, 4-dinitrophenylhydrazones with those of standard carbonyl compouds showed that formaldehyde, acetaldehyde, isobutyraldehyde, isovaleraldehyde, 2-methylbutyraldehyde and phenylacetaldehyde, respectively, were produced from the above amino acids. It was considered that each of the amino acids was deaminated and decarboxylated by hydrogen peroxide. Acetaldehyde was also formed from sodium glutamate, aspartic acid and threonine. In the case of serine, formaldehyde was detected as a main reaction product. The amount of formaldehyde formed from serine was larger than that from glycine. “Kamaboko”, “Hanpen”, herring roe and noodles which had been pretreated with hydrogen peroxide were found to have two to eight carbonyl components by thin layer chromatography. Acetaldehyde may be produced through the action of hydrogen peroxide on sodium glutamate, which is usually added to “Kamaboko” and “Hanpen” in large amounts.