PubMed · 11050989
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T B Whitaker. 2001. Sampling techniques.. https://doi.org/10.1385/1-59259-064-0%3A11
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Aflatoxin (AF) contamination poses a severe global threat to food and medicinal material safety, yet existing research focuses on terminal AF metabolites while neglecting residual biosynthetic precursors, leading to potential underestimation of contamination risks. In this study, a UPLC-MS/MS method was established for the simultaneous quantification of six AFs and their five precursors in lotus seeds, with optimization of mass spectrum parameters, chromatographic separation conditions, and sample pretreatment. Method validation confirmed linearity (R2 > 0.99), LODs (0.03-0.36 μg/kg), and recoveries (76.53%-120.0%, RSD < 15%). Analysis of 41 natural lotus seed samples revealed a 63.4% AF contamination rate, dominated by B-group AFs, while O-methylsterigmatocystin (OMST) and versicolorin hemiacetal (VOH) were identified as the primary co-residual precursors with co-occurrence rates ≥ 50%. Notably, AFM1 was predominantly detected in natural samples with AFB1 concentrations exceeding 100 μg/kg. Artificial inoculation experiments further demonstrated that sterilization and sealing conditions modulated AF biosynthesis in lotus seeds, with non-sterilized and non-sealed groups showing delayed fungal metabolism and lower toxin accumulation. A significant linear correlation was observed between AFM1 and AFB1 levels (r = 0.94) in infected samples, demonstrating their accumulation levels are coupled with fungal overall metabolic flux. Given the high co-occurrence rate of OMST/VOH with AFB1 in natural samples, their individual and combined toxicities require in-depth investigation. This work deciphers matrix-specific AF dynamics in lotus seeds, supporting regulatory standard refinement (e.g., precursor inclusion) and targeted control (e.g., time-sensitive drying after harvest). Further studies will focus on exploring the molecular mechanisms of substrate-dependent AF synthesis.
Processed (green) coffee beans from Coffea arabica in Brazil were assessed for the presence of Aspergillus and Penicillium species both before and after surface sterilisation, the aflatoxigenic and ochratoxigenic potential of the isolates and ochratoxin A levels. Contamination by Aspergillus and Penicillium species was found on 96% and 42%, respectively, of 45 samples from 11 localities. After disinfection with 1% sodium hypochlorite, the levels fell to 47% and 24%, respectively. One hundred and eighty isolates were identified to species level and comprised Aspergillus sections Circumdati (10 species), Flavi (3), Nigri (3), Versicolores (4), while two were teleomorphic species. Eight species of Penicillium were isolated. Within section Circumdati, 75% of the isolates produced ochratoxin A and all except Aspergillus elegans and Aspergillus insulicola have previously been reported to produce ochratoxin A. One-third of the 18 isolates of Aspergillus flavus produced aflatoxin B1 and B2. None of the isolates belonging to Aspergillus section Nigri or Penicillium produced ochratoxin A. Of the 40 bean samples analysed, 58% were infected with potentially ochratoxigenic fungi but only 22% of these were contaminated with ochratoxin A at levels that varied from 0.47 to 4.82 ng/g, with an average contamination level of 2.45 ng/g.
This report describes a simple, rapid and reliable method for screening the aflatoxin production by moulds of the Aspergillus flavus group. Strains were cultivated on yeast extract agar to which methylated beta-cyclodextrin derivative plus sodium desoxycholate was added. Production of aflatoxins was readily detectable by direct visualisation of a beige ring surrounding colonies after an incubation time of 3 days at 28 degrees C. When this ring was examined under UV light, it exhibited blue fluorescence. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by HPLC with fluorescence detection.