No abstract

No abstract

A technique referred to as 'linked-column immunoassay clean-up', was developed for the simultaneous determination of aflatoxins and ochratoxin A in a range of dry cereal-based pet foods and wild bird food. In addition a method also based on clean-up using immunoaffinity columns was used for the determination of fumonisin mycotoxins in samples known or suspected to contain maize. One hundred samples of pet foods consisting of 35 samples of domestic bird seeds and 15 samples of wild bird food were examined for aflatoxins B1, B2, G1 and G2 and ochratoxin A. Twenty samples of these samples were also examined for fumonisins B1 and B2. Limits of detection were about 0.5 micrograms/kg for each aflatoxin and ochratoxin A and 3 and 8 micrograms/kg for fumonisins B1 and B2 respectively. Eighty-four percent of the samples contained no measurable concentrations of mycotoxins. A low level of aflatoxin B1 was found in a sample of cat food and a concentration of 370 micrograms/kg aflatoxin B1 in one sample of peanuts marketed for wild birds. Ochratoxin A was detected in 10% of samples but in low concentrations, the highest of 7 micrograms/kg occurring in a sample of bird food. Fumonisins were found in 30% of the 20 samples tested with a maximum of 750 micrograms/kg total fumonisins being found in a sample of cat food. Five samples each of dog and cat foods were examined for mould count and fungal species as received and after storage under controlled simulated damp conditions. Mould counts in all 10 samples examined were very low when received. The samples in which moisture content had been increased contained visible mould after storage. Penicillium, Eurotium and Aspergillus were the predominant species. However, no ochratoxin A or aflatoxins were detected in these spoiled samples.

A multi-toxin method was developed for the detection of some of the known Alternaria mycotoxins, altenuene, iso-altenuene, alternariol, alternariol monomethyl ether, tenuazonic acid and altertoxin I in oilseed rape meal and sunflower seed meal. The method involves extraction of the toxins with an acidified mixture of acetonitrile: aqueous potassium chloride solution, followed by liquid-liquid extraction and further purification using gel permeation chromatography. The final extract is then examined on a reverse phase high performance liquid chromatographic gradient system with both fluorescence and UV detection. The average recoveries found were 94, 84, 109, 85, 66 and 93% for spiked oilseed rape meal samples and 91, 89, 96, 75, 61 and 102% for spiked sunflower meal samples with limits of determination of about 40, 50, 50, 40, 350 and 200 micrograms/kg for the above toxins, respectively. Detection limits were about 30% of these values. Thirty samples of oilseed rape meal and 22 samples of sunflower meal were examined using the methods developed. Twenty of the oilseed rape products which had been grown in the UK were free from contamination while 10 contained one or more of tenuazonic acid, alternariol and alternariol monomethyl ether. In contrast, all of the sunflower meal samples, of Argentinean, Indian or EC origin, were contaminated with one or more of alternariol, alternariol monomethyl ether and tenuazonic acid. Average levels of alternariol, alternariol monomethyl ether and tenuazonic acid were 68, 55 and 730 micrograms/kg, respectively for the contaminated samples of oilseed rape meal and 180, 100 and 1900 micrograms/kg, respectively for the contaminated samples of sunflower seed meal.

Methods used previously for the determination of aflatoxins B1, B2, G1 and G2, ochratoxins A and B, cyclopiazonic acid, zearalenone, sterigmatocystin, and moniliformin in maize were applied successfully to rice bran. However, recovery of deoxynivalenol and other trichothecene mycotoxins spiked into samples was lower than expected and no citrinin could be recovered. Forty samples of rice bran used in the animal feed industry were examined for the presence of 20 mycotoxins. The level of contamination of rice bran by mycotoxins was low. Aflatoxin B1 was present in 29 (72.5%) samples, usually together with related aflatoxins, up to a total of 28 micrograms/kg after allowing for recovery losses. Ochratoxin A at a level of 12 and 3 micrograms/kg was confirmed in two samples, while most samples also appeared to contain small concentrations of ochratoxin A. A chromatographic peak corresponding to cyclopiazonic acid occurred in several samples and one sample appeared to contain a low level of moniliformin. Positive confirmation of these last two mycotoxins was difficult and these findings must be regarded with caution. No other toxins were detected.

A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2, AFG1 and AFG2 in palm kernel samples has been developed by optimizing the sample preparation, solvent extraction, sample clean-up and quantification procedures. The aflatoxins are extracted from a slurried palm kernel sample with an acetone-water (80 + 20, v/v) mixture and the crude extract is cleaned up by solid-phase extraction using a phenyl bonded phase cartridge. The extract is passed through the cartridge with a water-methanol (93 + 7) mixture. Subsequent elution of the aflatoxins retained on the cartridge is achieved with a 3 ml aliquot of chloroform. The aflatoxin content of the eluate is quantified using a bi-directional high-performance thin-layer chromatography procedure. A critical evaluation of the proposed method was carried out by statistical comparison with the British Standard Method. The proposed procedure was shown to be more efficient and precise. Consistent recoveries of over 90% were achieved from spiked palm kernel extracts and detection limits were found to be 3.7, 2.5, 3.0 and 1.3 micrograms kg-1 for AFB1, AFB2, AFG1 and AFG2 aflatoxins, respectively.

No abstract

No abstract