Solid-phase microextraction (SPME) is a modern, solvent-free sample preparation technique, commonly used in trace analysis. This technique has been developed to combine sampling and sample preparation in one step. This paper reviews selected theoretical and practical aspects of the SPME method used for the isolation and preconcentration of impurities, food constituents, additives and flavour compounds in food samples. The main parameters affecting the extraction effectiveness are discussed and exemplified by selected chromatograms. The review is intended for readers who are either new to the field of SPME or its use in food analysis and many examples of its application for different food matrices are listed.
Based on the sequence of the ochratoxin A polyketide synthase gene (otapksPV), a polymerase chain reaction (PCR) system for the specific detection of Penicillium verrucosum in wheat has been developed. In a further approach, a real-time PCR system has been applied to determine the growth kinetics of P. verrucosum in wheat at cell numbers above 10(3) colony-forming units (cfu) ml(-1). The data obtained by real-time PCR correlated well with the data obtained by the plate count technique. For this purpose, the DNA was isolated directly from contaminated wheat without any further enrichment step. In a reverse transcriptase real-time PCR, the expression of the otapksPV gene in wheat was detected 22 days after inoculation and storage at ambient temperature. Reasonable amounts of ochratoxin A, however, could not be detected before day 30. This early activation of ochratoxin A related genes was confirmed by microarray analysis.
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