Mycological examination was carried out on a total of 105 samples of buckwheat and its products including 16 batches of grains, 57 of flours and 32 of dried noodles. All samples were collected from marketing channeles in Tokyo. Representative strains of the isolates from these samples were examined chemically for their producing ability of carcinogenic mycotoxins such as aflatoxins and sterigmatocystin. To isolate fungi was applied the modified Inagaki and Kurata's method, which used two kinds of Potato Dextrose Agar medium containing either 20% glucose or 100μg chloramphenicol per ml.
Filamentous fungal counts of the grains, flours and noodles were estimated as 3-88/50 grains (average 51), 100-46, 250/gram (average 6, 055) and 50-7, 025/gram (average 1, 178) respectively.
Predominant genera of fungi among the total fungal isolates (383, 708) from all the samples examined were the genera of
Aspergillus, Penicillium and
Cladosporium. Of the total isolates, 3, 389 isolates (0.9%) were found to be the
Aspergillus flavus group, and 48, 428 (12.6%) and 1, 357 (0.4%) isolates were identified as
Aspergillus versicolor and
Fusarium spp. respectively. Results of the bioproduction test with chloroform extracts of culture filtrates of the isolates indicated that one each strain of
A. flavus and
Rhizopus sp. from the grains samples were found to be producing aflatoxin B
1 and B
2 simultaneously. Of the aflatoxins-producing strains belonging to the
A. flavus, three strains from the flours showed to have the aflatoxin producing ability (aflatoxin B 15.2-29.2ppm) as high as that of
A. flavus NRRL 3000 used as the references strain. One strain of
A. versicolor from the flour was recognized as sterigmatocystin-producing strain.
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