Blood plasma samples collected from 144 healthy volunteers in 16 locations across Canada in 1994 were analysed for ochratoxin A (OTA). The method of analysis included cleanup by C18 solid phase extraction and immunoaffinity columns followed by liquid chromatography (LC) with fluorescence detection, which gave 86.5% (s.d. = 9.7) recovery (n = 31) of OTA (added at 2 ng/ml) with a detection limit of 0.15 ng/ml. The arithmetic mean concentration found in the plasma samples, corrected for volume of anticoagulant added, was 0.88 ng/ml with a standard deviation of 0.35 ng/ml and a range of 0.29-2.37 ng/ml. Confirmation of identity of OTA was by methyl ester formation for 65 samples and by LC-tandem mass spectrometry for 17 samples (some of which were included in pooled samples). Statistical analysis, by ANOVA of the log OTA plasma concentrations, showed a highly significant effect due to location in Canada (p = < 0.0001) but no effect due to age, sex or blood group of donors. The highest mean concentration was found in Winnipeg, significantly different (p = 0.05) by the Student-Newman-Keuls multiple range test from the lowest levels found in Toronto, Vancouver and Saint John.
Because of concern about possible transmission of ochratoxin A (OA) from contaminated grain adjuncts, development of a sensitive method for its determination in beer was investigated. Solid phase extraction (SPE) on C-18 and silica gel columns in series and on an immunoaffinity column (OchraTest) were used to obtain extracts for quantitation by reverse phase liquid chromatography with fluorescence detection. The standard curve was linear in the range 2.5-50 pg OA injected and detection limits for both methods were of the order 0.05-0.1 ng/ml beer (signal to noise 3:1). Per cent recovery of OA from various beer samples spiked at a level of 1 ng/ml averaged 82-100% for three modifications of the SPE method and 97% for the immunoaffinity column method. Forty-one samples of Canadian and imported beers were analysed. Trace levels of OA (< or = 0.2 ng/ml) were detected in 26 samples by SPE and/or immunoaffinity column methods; there was generally good agreement between the methods. Identity of OA was confirmed by methyl ester formation in five samples cleaned up by the immunoaffinity column procedure.
Ochratoxin A (OA), fumonisin B1 (FB1) and fumonisin B2 (FB2) were added to wort at levels of 0.19, 0.95 and 0.95 micrograms/ml, respectively, and fermented for up to 8 days by three strains of Saccharomyces cerevisiae. Decreases of OA in the beer over this period were estimated from straight line slopes to be 2-13%. Losses of FB1 and FB2 were estimated to be 3-28% and 9-17% respectively. Some OA was taken up by the yeast, up to 21% in a detailed study with one strain. In contrast, uptake of fumonisins by yeast was negligible (< 1% FB1 and < 2% FB2). In control experiments, OA, FB1 and FB2 were found to be stable when added to yeast-free wort and kept for up to 8 days at 25 degrees C. In addition, spiking experiments with blank day 0-8 fermenting wort samples showed method recoveries averaging 87-91%. None of the mycotoxins was detected in control fermentations where they were not added to the wort.
A sensitive method was developed for the determination of deoxynivalenol (DON), nivalenol (NIV), alpha-zearalenol (alpha-ZEL), beta-zearalenol (beta-ZEL) and zearalenone (ZEN) in beer by capillary gas chromatography-mass spectrometry (GC-MS) of their heptafluorobutyrate (HFB) derivatives. Recoveries averaging 90-103% were obtained from beers spiked with each mycotoxin in the 5-20 ng/ml concentration range. Limits of detection were 0.1-1.5 ng DON/ml, 0.01-0.3 ng NIV/ml, 2.5-3 ng alpha- and beta-ZEL/ml, and 1.5-2 ng ZEN/ml. Twenty-nine of 50 samples of Canadian and imported beer surveyed were found to contain DON; of these nine contained greater than 5 ng/ml (up to 50 ng/ml). The identity of DON was confirmed by response ratios at m/z 670 and m/z 884 for the HFB derivative and m/z 497 and m/z 512 for the trimethylsilyl (TMS) derivative. NIV was also detected in three beer samples (0.1-0.84 ng/ml) but no alpha-ZEL, beta-ZEL or ZEN was found.
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