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Molds isolated from visibly molded cheeses in shops, households, and warehouses have been identified. Mold flora of cheeses in shops and households consisted mainly of Penicillium verrucosutn var. cyclopium. On cheeses ripening in warehouses, Penicillium verrucosum var. cyclopium, Aspergillus versicolor, Aspergillus repens, and Penicillium verrucosum var. verrucosum were the dominant mold species. Cheeses ripening in warehouses and molded with A. versicolor were examined for sterigmatocystin. Nine of 39 cheese samples contained sterigmatocystin in the surface layer in concentrations ranging from 5 to 600 µg/kg

The effect of water activity (aw) on growth and aflatoxin production by Aspergillus parasiticus NRRL 2999 was determined using submerged cultures in which the aw was adjusted by addition of glycerine, glucose, or a mixture of salts. At a sub-optimal aw aflatoxin production was low in the glycerol and glucose media while no strong inhibition of mycelial growth occurred. A similar effect was obtained in surface cultures on agar media in which the aw was adjusted by addition of glycerine or sucrose. The effect of a sub-optimal temperature was the reverse; compared to inhibition of mycelial growth in surface cultures, the effect on aflatoxin production was slight. No detectable quantities of aflatoxin B1 were formed at 0.83 aw and at 10 C nor at four combinations of higher aw and temperature. The aw was measured by a recently developed device using the dewpoint principle.

Moulds are able to produce extracellular polysaccharide antigens which are heat-stable and almost genus specific. Of 44 different strains of Penicillium 41 (93%) and all 12 strains of Aspergillus tested produced detectable quantities of an immunologically related antigen. Additionally 10 of these 56 strains produced an antigen immunologically related to the antigen produced by the genera Mucor and Fusarium. Immunologically different, but genus-specific antigens were produced by each of the species belonging to the genus Geotrichum, Fusarium, Cladosporium, Mucor and Rhizopus. The antigens produced by Mucor and Rhizopus, however, were immunologically related.

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The polymerase chain reaction (PCR) was used as a tool for the detection of enterotoxigenic Escherichia coli in minced meat. With two synthetic 29-mer oligonucleotides, a 195-bp fragment from the E. coli heat-labile enterotoxin (LT) gene could be amplified specifically. When 6 CFU was added to the reaction mixture as a template, the PCR yielded sufficient amplified product for visualization on an agarose gel. Prior to PCR amplification, the minced meat samples were subjected to enrichment culturing for E. coli. From these cultures, 10 ,ul was used in the PCR assay. All 20 25-g samples that were examined in this assay were negative for E. coli LT. However, when 3 CFU of E. coli LT was added to the 25-g samples of minced meat prior to enrichment culturing, the PCR assay yielded positive results.

In 1991 and 1993 cereals were sampled during harvest in The Netherlands. The samples were tested for the presence of molds and the samples of 1993 were additionally tested for the mycotoxins deoxynivalenol and zearalenone. The molds were identified to genus level and those belonging to the genus Fusarium to species level. The total fungal infection of cereals in 1991 did not differ from 1993, with a median value of 5.0 log CFU g−1 in both years. The incidences of the genera Aspergillus, Penicillium, the group of Mucor and Rhizopus, Cladosporium, and Fusarium differed considerably between the two years, possibly caused by the different weather conditions. The numbers of samples infected with Fusarium were much higher in 1993 (83%) than in 1991 (34%). In 1991, no Fusarium was detected in samples from the southern part of The Netherlands, as opposed to 1993, when Fusarium was found in all regions sampled. The most dominant Fusarium species in 1991 were Fusarium culmorum and Fusarium avenaceum. In 1993, Fusarium poae, Fusarium culmorum, and Fusarium crookwellense dominated. All these Fusarium species are known mycotoxin producers. Three percent of the cereal samples of 1993 contained deoxynivalenol and 1% contained zearalenone in levels of over 500 μg kg−1 and 200 μg kg−1, respectively. This study has shown that the incidences of various fungal genera and Fusarium species in cereals in The Netherlands can vary from year to year. Considerable numbers of toxigenic Fusarium molds can occur and Fusarium mycotoxins may be present.