It was investigated that a simultaneous separation of 10 kinds of Synthetic Organic Food Colors permitted in Japan by application of high speed liquid chromatography. (Green#3 was excluded by reason which is not in general use.) Completely simultaneous separation became possible by using a gradient system with octadecylsilane column and ammonium carbonate solution-methanol as a mobile phase. Then we applied this method to goods on the market, which were mixed color preparations and chocolate, and obtained satisfactory results.
Investigation in relation to R plasmids was performed on 217 strains of drug resistant Escherichia coli isolated from 100 samples of ground pork in 1972 to 1974. Drugs tested were 7 kinds such as tetracycline (TC), chloramphenicol (CM), streptomycin (SM), sulfanilamide (SA), kanamycin (KM), ampicillin (APC) and nalidixic acid (NA). The results were summarized as follows; 1. Of 217 strains, about 95% were of multiple resistance, while the rest were of single resistance. 2. Among 217 strains, 104 (47.9%) strains were found to carry R plasmids. Especially, multiple resistant strains with APC resistance carried R plasmids at the frequency of about 86% to 100%. 3. The most frequent resistance pattern of R plasmids were multiple resistance. 4. Transmission frequency of R plasmids derived to E. coli K-12 ML1410 were about 10-4 to 10-6 per one donor. 5. Drug resistant E. coli strains carried two types of R plasmids i. e., fi- R (20%) and fi+ R plasmid (80%).
Polyphosphates show relatively strong antibacterial activity against some bacteria. The use of polyphosphates as food preservative have been studied. In this study sodium hexametaphosphate (HP) was mainly used as polyphosphate, Bacillus subtilis and Escherichia coli as tested bacteria. The action of HP on these bacteria was investigated and the following results were obtained. The prolongation of lag time was observed in the growth of B. subtilis pretreated with HP for 60 minutes at 30°C. It was found that both lysozyme and penicilline showed strong antibacterial activity against B. subtilis pretreated as above. Ribonucleic acid related substances of low molecular weight were released from the cells of B. subtilis by HP-treatment. On the other hand, HP showed little antibacterial activity against E. coli under the same experimental condition. From these results, it was deduced that the differences of the antibacterial activity of HP against B. subtilis and E. coli were based on the structural differences in cell envelope of them.
Though sodium hexametaphosphate (HP) had little antibacterial activity against Escherichia coli, HP showed the strong antibacterial action on E. coli in the presence of surface-active agents such as cholate (CA), dodecylbenzenesulfonate, sodium dodecylsulfate and monocaprin. HP masked with Ca2+ vanished the activity completely in spite of the presence of CA. HP scarcely exhibited the activity against E. coli pretreated with CA. That is, it appears that the combined use of CA and HP is necessary in order to enhance the antibacterial activity of HP against E. coli. The experiment of preservative effect by the combined use of HP and monocaprin was conducted with raw Japanese noodle. In this experiment it was confirmed that the combined use of them is more effective than the use of HP or monocaprin alone.
Yeast florae of twelve samples of commercially available cheese imported from Europe and North America were investigated. Five samples out of twelve were found to contain 106-108/g of yeasts. In three kinds of blue cheese, Superzola, Roquefort, and Valencay, Debaryomyces hansenii and its imperfect counterpart, Torulopsis candida, were the exclusive species of the florae. About 90% of yeast flora was occupied by D. hansenii-T. candida, and the remaining 10% by Candida zeylanoides in the case of Plumrose (blue cheese). Geror, a non-ripening cheese, contained 105-108/g of Candida lipolytica, and D. hansenii was the minor constituent of the yeast flora. Only a small number of yeasts were found in Baby Edam, Cheddar, Camembert, and Viola (cream) cheese, and no yeast was detected in Emmental cheese. In addition to the species mentioned above, Kluyueromyces lactis, Saccharomyces italicus, Sporobolomyces roseus, Candida intermedia, Candida kefyr, Cryptococcus albidus, Cryptococcus luteolus, Rhodotorula rubra, and Rhodotorula minuta were detected as minor members of microflora of eleven samples. The yeast florae of blue cheese found in the present investigation differed from those previously reported in cheese during the ripening. This suggests a possible change of yeast flora in blue cheese after ripening.
Two hundred and fifteen isolates of yeasts obtained from 21 samples of cheese imported from Europe and North America were studied taxonomically and were identified with 15 species belonging to 9 different genera. More than a half of the isolates (134) were Debaryomyces hansenii, and followed by Candida lipolytica (27), Candida zeylanoides (14), Torulopsis candida (13), Cryptococcus albidus (11), Kluyveromyces lactis (3), Torulopsis sphaerica (3), Cryptococcus luteolus (2), Rhodotorula rubra (2), Saccharomyces italicus (1), Sporobolomyces roseus (1), Candida intermedia (1), Candida kefyr (1), Rhodotorula minuta (1), and Trichosporon cutaneum (1). One hundred and thirty-four isolates of D. hansenii were divided into 4 subgroups by assimilation of lactose, formation of a pellicle, and colonial characteristics. More than a half of the isolates (61%) belonged to D. hansenii-type (assimilates lactose, and forms a pellicle and rough colony), and followed by D. subglobosus-type (34%, assimilates lactose, and not forms a pellicle, and smooth colony), D. nicotianae-type (3%, not assimilates lactose, and forms a pellicle, and smooth colony), and D. kloeckeri-type (2%, not assimilates lactose, and not forms a pellicle, and rough colony). The subgrouping has little taxonomic value since several isolates showed intermediate characteristics but has a value from an ecological point of view. Isolates belonging to Cr. albidus showed characteristics resembled those of Cr. albidus var, albidus and Cr. albidus var. diffluens but could not be clearly separated into these two varieties because some isolates showed intermediate properties between the varieties. These two varieties should be combined.
A method for quantitative determination of nano gram level of benzo[a]pyrene (BP) in foodstuffs using tritiated BP (3H-BP) was described. Extracts from foodstuffs, having been added a certain amount of 3H-BP, were fractionated by column chromatography on Florisil, and thinlayer chromatography on acetylated cellulose. Concentration and radio activity of BP in the final fraction were determined by fluorescence spectrometry and liquid scintillation. Recovery ratio of each experiment was obtained by comparing the radio activities of added 3H-BP and separated BP. Concentration of BP in the sample analyzed was calculated from the amount of isolated BP and the recovery ratio in each experiment. A quantitative limit of BP by this method was 0.2 ppb when 50 g of sample was used. By this method, contents of BP in each sample of Tenpura oil, salad oil, flour, and polished rice were determined as 0.6, 0.2, 0.1, and <0.1 ppb on average, respectively.
The contents of 3, 4-benzopyrene, 1, 2-benzanthracene, 1, 2, 5, 6-dibenzanthracene and chrysene in raw and broiled fishes were determined. (1) Raw fishes; These polycyclic aromatic hydrocarbons were not detected. (2) Gas broiled fishes; 3, 4-benzopyrene, 1, 2-benzanthracene and chrysene were detected at maximum 0.75μg, 0.39μg and 0.98μg/100g respectively. In particular, 3, 4-benzopyrene was detected over all gas broiled fishes. But 1, 2, 5, 6-dibenzanthracene was not detected. (3) Gas broiled fishes wrapped in aluminium-foil; These polycyclic aromatic hydrocarbons were not detected except chrysene. It was also found that polycyclic aromatic hydrocarbons' formation correlated with lipid contents in fishes. The lipid fraction of fish was found to be main source of polycyclic aromatic hydrocarbons when the fish was broiled.
After establishing the screening method for detecting Cl. perfringens enterotoxin, its production by these organisms of various origins was examined, and the characterization of enterotoxin-producing strains was attempted. 1. The micro-cell-culture technique, using the serial dilutions of 45hr culture supernatant of G. K medium inoculated with heat-treated thioglycollate culture and VERO cell suspensions, was the combenient system for the screening test. 2. The enterotoxin-producing strains were detected from all of 9 different food poisoning cases (27 out of 33 strains of food poisoning origin), while none of 54 strains isolated from human feces or various soil samples produced this toxin. This implies that the close relationship exists between Cl. perfringens food poisoning and the enterotoxin. 3. Heat resistant and enterotoxin-producing strains of food poisoning origin could not be distinguished from other strains isolated from healthy human feces in relation to the Hobb's serological type, toxin production, sporulation and other biochemical characters. 4. The sporulation ratio was found to be decreased in case enterotoxin positive strains became negative during storage, although the frequency of this change was not very high.
By use of AE (Azide Esculin) agar plate method enterococci were obtained from 37 of 89 insect samples collected from Tokyo and neighbouring areas during July to December 1974, in numbers from 103 to 108/g of insect. Seventy nine strains of enterococci isolated from 37 insects were studied by means of the biochemical tests: fermentation of mannitol, sorbitol, arabinose, glycerol, melezitose and melibiose, liquefaction of gelatine, nutritional requirement of folic acid, reduction of triphenyltetrazolium chloride, and growth in 0.04% pottassium tellurite. Fifty one strains from 30 insects were identified as Streptococcus faecalis subsp. liquefaciens, 15 from 10 insects as S. faecalis, and 13 from 8 insects as S. faecium. The majority of S. faecalis subsp. liquefaciens and S. faecalis isolates conformed exactly in their biochemical test pattern to the typical organisms of human origin. On the other hand all the S. faecium isolates deviated in one or more biochemical properties from typical S. faecium.