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Modern methods in cereal grain mycology

Olsson, Johan (2000). Modern methods in cereal grain mycology. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae. Agraria, 1401-6249 ; 241
ISBN 91-576-5792-0
[Doctoral thesis]

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Abstract

A simple rapid DNA extraction method, equally suitable for spores and mycelia is proposed. Heating samples in NaOH and SDS provides DNA of high purity, suitable for Polymerase Chain Reaction (PCR) analysis. For Penicillium roqueforti the detection limit was 6 x lo3 conidia and 1 mg (fresh weight) mycelium in the extraction liquid. The method proved efficient with Aspergillus jlavus, Fusarium graminearum, Rhizopus stolonifer, Eurotium herbariorum, and Cladosporium herbarum, as well. An optimised competitive PCR (cPCR) method for quantifying fungal growth in cereal grain was developed using experimental design. DNA extraction efficiency was quantified by cPCR using primers specific for the internal transcribed spacers (ITS) of the ribosomal DNA of P. roqueforti. The proposed method can detect P. roqueforti at levels as low as 10' CFU/g grain and at levels higher than lo2 CFU/g grain. Quantification is consistent (CV < 8%) and highly correlated with results from traditional dilution plating. The possibilities of using an electronic nose or gas chromatography combined with mass spectrometry (GC-MS) to quantify ergosterol, colony forming units (CFU), ochratoxin A, and deoxynivalenol (DON) in naturally contaminated barley samples was investigated. The main volatile compounds of grain with normal odour were 2-hexenal, benzaldehyde and nonanal, while 3-octanone, methylheptanone and trimethylbenzene were the main volatile compounds of grain with off-odours. Both CFU and ergosterol levels could be predicted from data from either GC-MS or electronic nose measurement. It was also possible to classify the ochratoxin A level as either <5 or >5 pgkg cereal grain, and estimate the DON level. Samples with ochratoxin A levels below 5 pgkg had higher concentration of aldehydes (nonanal, 2-hexenal) and alcohols (I-penten-3-01, 1 octanol). Samples with ochratoxin A levels above 5 pgkg had higher concentration of ketones (2-hexanone, 3-octanone). Pentane, methylpyrazine, 3-pentanone, 3-octene-2-01 and isooctylacetate were positively correlated with DON, while ethylhexanol, pentadecane, toluene, I-octanol, I-nonanol, and 1-heptanol were negatively correlated with D

Authors/Creators:Olsson, Johan
Title:Modern methods in cereal grain mycology
Year of publishing :January 2000
Volume:241
Number of Pages:37
Papers/manuscripts:
NumberReferences
ALLI. Olsson, J., Schnürer J., Pedersen, L.H. and Rossen, L. (1999). A rapid and efficient method for DNA extraction from fungal spores and mycelium for PCR-based detection. Journal of Food Mycology. 2: 25 1- 260. II. Boysen, M.E., Pedersen, L.H., Olsson, J. and Schnürer J. Quantification of Penicillium roqueforti in cereal grain with competitive PCR. (Submitted) III. Olsson, J., Börjesson, T., Lundstedt, T. and Schnürer J. (2000). Volatiles for mycological quality grading of barley grains - determinations using gas chromatography-mass spectrometry and electronic nose. International Journal of Food Microbiology. 59: 167-178. IV. Olsson, J., Börjesson, T., Lundstedt, T. and Schnürer J. Detection and quantification of ochratoxin A and deoxynivalenol in barley grains by GC-MS and electronic nose. (Submitted) Papers I and III are printed with permission of the respective publishers
Place of Publication:Uppsala
ISBN for printed version:91-576-5792-0
ISSN:1401-6249
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:Q Food science > Q03 Food contamination and toxicology
H Protection of plants and stored products > H01 Protection of plants - General aspects
J Handling, transport, storage and protection of agricultural products > J11 Handling, transport, storage and protection of plant products
Subjects:Not in use, please see Agris categories
Agrovoc terms:grain, cereals, mycology, penicillium roquefortii, aspergillus flavus, gibberella zeae, rhizopus stolonifer, eurotium, cladosporium herbarum, pcr, gas chromatography, ergosterol, ochratoxins, vomitoxin
Keywords:electronic nose, GC-MS, quantification, mould, fungi, grain-kernels, polymerase chain reaction, competitive PCR, DON, ochratoxin A, CFU, ergosterol, fungal volatile metabolites
ID Code:9
Department:(NL, NJ) > Dept. of Microbiology (until 161231)
Deposited By: Staff Epsilon
Deposited On:23 Apr 2002 00:00
Metadata Last Modified:02 Dec 2014 10:01

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