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- Schnürer, Johan, 1957-, et al.
(författare)
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Ergosterol Levels and Mould Colony Forming Units in Swedish Grains of Food and Feed Grade
- 1992
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Ingår i: Acta Agriculturae Scandinavica - Section B. - Oslo, Norway : Scandinavian University Press. - 0906-4710 .- 1651-1913. ; 42:4, s. 240-245
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Tidskriftsartikel (refereegranskat)abstract
- Although ergosterol is considered to be a suitable indicator of mould growth in cereal grains, there are few reference values available for Scandinavian conditions. We have determined the ergosterol levels in Swedish grain of different origins: cleaned food-grade wheat from a commercial mill, feed-grade cereals (oats and barley) with different odours and cereals (winter wheat, ''American wheat'', triticale and rye) from various field trials conducted in south-central Sweden in 1990. Specific objectives were to elucidate the relationships between ergosterol levels and numbers of mould colony forming units (CFU) and between ergosterol and grain odour.Ergosterol levels in the food-grade wheat ranged between 2.4 and 2.8 mug/g DW, and between 3.0 and 5.6 mug/g DW in the field trial cereals, while values in most of the feed grain samples ranged from 8-15 mug/g DW The levels agree with other published data for European grains.A positive correlation was found between numbers of colony-forming units and ergosterol concentration. The degree of correlation was higher when numbers of CFU were determined on dichloran-glycerol 18% agar with a low water activity (aw = 0.95) than on malt extract agar (aw = 0.99). There was no agreement between ergosterol levels and grain odour, since even samples described as having a fresh smell had high ergosterol levels. However, the highest level (33 mug/g DW) was found in a sample with a pronounced musty odour, and the lowest (1.1 gg/g DW) in a sample that smelled as if it had been heat damaged.
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2. |
- Borjesson, T., et al.
(författare)
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Volatile metabolites produced by six fungal species compared with other indicators of fungal growth on cereal grains
- 1992
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Ingår i: Applied and Environmental Microbiology. - Washington : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 58:8, s. 2599-2605
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Tidskriftsartikel (refereegranskat)abstract
- Six fungal species, Penicillium brevicompactum, P. glabrum, P. roqueforti, Aspergillus flavus, A. versicolor, and A. candidus, were inoculated on moistened and autoclaved wheat and oat grains. They were cultivated in glass vessels provided with an inlet and outlet for air. Air was passed through the vessels to collect volatile fungal metabolites on porous polymer adsorbents attached to the outlet. Samples were collected at two fungal growth stages. Adsorbed compounds were thermally desorbed, separated by gas chromatography, and identified by mass spectrometry. Differences in the production of volatile metabolites depended more on the fungal species than on the grain type. The fungal growth stage was not an important factor determining the composition of volatiles produced. 3-Methylfuran was produced in similar amounts regardless of the fungal species and substrate (oat versus wheat). The production of volatile metabolites was compared with the production of ergosterol and CO2 and the number of CFU. The production of volatile metabolites was more strongly correlated with accumulated CO2 production than with actual CO2 production and more strongly correlated with ergosterol contents of the grain than with numbers of CFU.
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