The inhibitory effect of different food dyes, which are used for food additives at present, on pancreatic amylase was examined in vitro, following the establishment of assay method of the enzyme activity in the presence of the dyes.
The preincubation of enzyme and dye for a certain time was prerequisite for the appearance of inhibitory effect of the dye. Xanthene dyes except acid red showed the significant inhibition at the wide range of pH, which degree increased in order of eosine, erythrosine, phloxine and rose bengale. No other dyes tested except xanthenes inhibited the enzyme at neutral pH, whereas most of them showed the inhibition of 20 to 70% at pH 4.0.
The inhibitory effect of rose bengale was strongly enhanced by irradiation of the preincubation mixture under a fluorescent lamp, suggesting a photo-inactivation of the enzyme by this xanthene dye. The inhibition was also influenced by the co-existence of other substances; for example, sodium chloride stimulated the inhibition and sucrose and proteins repressed it. From the kinetie study, the type of inhibition of pancreatic amylase by rose bengale was non-competitive.

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In order to obtain a breaf information albout extent of Contamination of foodstuffs by fungi especially by Aspergillus flavus which is known to produce aflatoxin, fungal and bacterial examination of flours and cereals on sale, such as buckwheat flour, wheat flour, roasted soybean flour, soybean and peanut, were carried out. Isolated fungi were identlfied and aflatoxin productivity of A. flavus found among them was studied.
Test material was suspended and homogenized in phosphate buffer saline and mix-cultured in potato dextrose agar containing chloramphenicol. After 7 days incubation at 27°C, number of the colonies of fungi and yeasts developed were counted. Fungi and yeasts were found from 77% of the materials tested over all; and 100, 90, 45.5, 78.9 and 73.3% from buckwheat flour, wheat flour, roasted seybean flour, soybean and peanut, respectively. Number of fungi and yeasts in average in each foodstuffs tested were as follows: 23, 000/g in buckwheat flour, 240/g in wheat flour, 90/g in roasted soybean flour, 130/g in soybean and 280/g in raw non-shelled peanut.
Bacterial counts made on plain agar were as follows: 170, 000/g in buckwheat flour, 860/g in wheat flour, 130/g in roasted soylbean flour, 400/g in soybean and 540/g in raw nonshelled peanut. Degree of fungal contamination did not correlate with that of bacterial contamination. Moisture contents of the test materials also showed no correlation with degree of fungal or bacterial contamination.
The most prevaling genus among isolates of fungi was Penicillum (43.8%) and next one was Aspergillus (24.0%). In addition to them, Cladosporium (6.3%), Rhizopus (3.1%), Cephalosporium (2.1%), Scopulariopsis (2.1%), Epicoccum (2.1%), Paecilomyces (2.1%), Mortierella (1.0%), Gonatobotrys (1.0%), Botrytis (1.0%), Monilia (1.0%) and Mucor (1.0%) were also isolated.
Among 23 strains of the isolates of Aspergillus, 10 were identified as A. flavus, of which 7 were isolated from buckwheat flour and the others were from wheat flour. Five strains of them were proved to elaborate aflatoxin B₁ and/or B₂ in vitro. Most of them produced the toxin only in a small amount, but one strain which was isolated from wheat flour produced toxin B₁ in fairly large amount. It was estimated to be 23.2mg/kg of the mold rice medium by fluorodensitometric method. Toxicity of this toxin was tested by chicken embryo method. The value of LD₅₀ was 0.125μg/Egg.
Aflatoxin itself was not detected directly in the material from which A. flavus was isolated.

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It is well known that flea seed husk contains about 64% of non-digestible polysaccharide and also this husk has some laxative action. Then the nutritional studies of this husk were undertaken to confirm its suitability as dietetic food.
For the experiment, 60 male rats were divided into three groups, namely, control, 3 and 10% husk added diets groups, and animals were fed for 3 months with these diets and every day the body weight, and weights of feed intaken, of water drunken and also of feces excreted were measured.
The lower body weight gain was observed only with 10% husk added diet group, and 3% group showed almost the same growth as that of control group. By the administration of this husk, the amounts of feces excreted were increased, but there was no sign of diarrhea.
The weight of organ was measured about 10 organs, but there were no significant differences between these weights was of normal and those of 3% group, while these were significant between normal and 10% group.
The histological examination was also done with these organs of three groups, but the evident changes were not recognized.

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Azide esculin agar plate method (AE agar, 1% polypeptone, 0.5% yeast extract, 0.5% NaCl, 0.4% K₂HPO₄, 0.15% KH₂PO₄, 0.05% NaN₃, 0.1% esculin, 0.05% ferric ammonium citrate, 1.5% agar, pH 8.0) for enterococcus test of frozen foods was developed in this work.
Among 221 enterococcus strains including 179 strains freshly isolated from feces, polluted water and frozen foods, and 42 stock strains 217 (98.2%) strains formed typical colonies surrounded by black halos on AE agar plates after 24hr incubation at 45°C. On the other hand, 234 (96.3%) of 243 typical colonies produced in AE agar test of 26 frozen food samples were identified with enterococci by completed test. Using AE agar plate method and Most Probable Number (MPN) method of AC-AC (Azide Citrate) broth procedure, enterococcus counts of 50 frozen food samples were determined. It was shown that although enterococcus counts obtained by both methods were comparable, AE agar plate method was preferable to the MPN method because of the simplicity and rapidity of the test procedures.
AE agar plate test followed by AC broth confirmation test may successfully be used for a rapid determination of enterococci in frozen foods.

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Fifty samples of commercial frozen raw and prepared seafood products were tested for total bacterial counts, coliforms, enterococci and Escherichia coli. For the determination of coliforms desoxycholate agar plate method and lactose broth-BGLB Most Probable Number (MPN) method were used, while Azide Esculin (AE) agar plate method and ACAC MPN method according to Horie, et al. were used for enterococcus counts.
The values obtained with the plate method and the MPN method were fairly related both in the coliform and the enterococcus test. Relationships between total bacterial counts, coliform counts obtained by desoxycholate agar and enterococcus counts by AE agar were investigated. Enterococcus counts were more closely related to total counts than to coliform counts, while coliform counts were not so related to both the other two counts. On the other hand, E. coli was not detected except in only 3 samples.
Bacterial suspensions of coliforms and enterococci in 10% skim milk were frozen and storaged at -21°C for long period. Viable cell counts of coliforms decreased significantly during freezing and freezing strorage, furthermore, majorities of the survived population had lost the ability of colony-formation in desoxycholate agar. Conversely, enterococcus counts determined by AE agar remained relatively constant during the same storage period. In general, lower values of coliform counts of frozen food samples, as compared with enterococcus counts, may be considered to be caused by not only rapid death but also loss of the growth ability of coliform organisms in desoxycholate agar during freezing storage.
The result suggests that entrococci can be used advantageously in preferrence to coliforms as indicator of bacterial contamination before freezing of frozen seafood products.

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Peracetic acid acted on purine and pyrimidine bases, and these nucleosides. This action was markedly affected by pH in reaction media. Peracetic acid also acted on deoxyribonucleic acid (DNA). It has been revealed through the base analysis of DNA that one of the actions of peracetic acid on DNA is the action on the base constituents. Their decomposition by peracetic acid was stronger under acidic condition than under neutral or alkaline condition. In addition, the decrease of the viscosity of DNA solution was observed. It was suggested that the decrease may be due to degradation of DNA molecule such as the hydrolysis of internucleotidic linkages, etc.

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In Department of Toxicology, National Institute of Hygienic Sciences, chronic toxicity tests using γ-irradiated wiener sausage are carrying out. The authors studied on the fat oxidation in irradiated and non-irradiated wiener sausages mixed in rat feed respectively, and acid value, peroxide value and carbonyl value of crude fat were measured.
Remarkable differences between irradiated and non-irradiated samples were not observed. Peroxide value and carbonyl value of both feed samples changed little up to 4 weeks, but after that they increased rapidly. According to these results, it is concluded that these feed should be prepared every 4 weeks.

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