Aflatoxins in domestic and imported foods and feeds

Aflatoxins, metabolic products of the molds Aspergillus flavus and A. parasiticus, may occur in foods and feeds. These toxins cannot be entirely avoided or eliminated from foods or feeds by current agronomic and manufacturing processes and are considered unavoidable contaminants. To limit aflatoxin exposure, the U.S. Food and Drug Administration (FDA) has set action levels for these toxins in foods and feeds involved in interstate commerce. FDA continually monitors food and feed industries through compliance programs. This report summarizes data generated from compliance programs on aflatoxins for the fiscal year 1986. Commodities sampled included peanuts and peanut products, corn and corn products, tree nuts, cottonseed, milk, spices, manufactured products, and miscellaneous foods and feeds. Correlations were highest between aflatoxin contamination and geographical areas for corn/corn products and cottonseed/cottonseed meal. Higher incidences of aflatoxin contamination in corn and corn products designated for human consumption were observed in samples collected in the southeastern states (32 and 28%, respectively). A higher incidence of contamination was observed in corn designated for animal feed from Arkansas-Texas (74%) than from the southeastern states (47%). Only 3% of feed corn from corn belt states contained detectable aflatoxins. All aflatoxin-contaminated cottonseed was collected in the Arizona-California area; 80% of cottonseed meal analyzed from this area also contained detectable levels of aflatoxins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aflatoxin and fumonisin contamination of commercial corn (Zea mays) hybrids in Mississippi

Resistance to mycotoxin contamination was compared in field samples harvested from 45 commercial corn (maize) hybrids and 5 single-cross aflatoxin-resistant germplasm lines in years with high and moderate heat stress. In high heat stress, mycotoxin levels were (4.34 +/- 0.32) x 10(3) microg/kg [(0.95-10.5 x 10(3) microg/kg] aflatoxins and 11.2 +/- 1.2 mg/kg (0-35 mg/kg) fumonisins in commercial hybrids and 370 +/- 88 microg/kg (140-609 microg/kg) aflatoxins and 4.0 +/- 1.3 mg/kg (1.7-7.8 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. Deoxynivalenol was detected (one-fourth of the samples, 0-1.5 mg/kg), but not zearalenone. In moderate heat stress, mycotoxin levels were 6.2 +/- 1.6 microg/kg (0-30.4 microg/kg) aflatoxins and 2.5 +/- 0.2 mg/kg (0.5-4.8 mg/kg) fumonisins in commercial hybrids and 1.6 +/- 0.7 microg/kg (0-7 microg/kg) aflatoxins and 1.2 +/- 0.2 mg/kg (0.5-3.0 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. The results are consistent with heat stress playing an important role in the susceptibility of corn to both aflatoxin and fumonisin contamination, with significant reductions of both aflatoxins and fumonisins in aflatoxin-resistant germplasm lines.     

Mycoflora and fumonisin contamination in Brazilian corn from sowing to harvest

The present study aimed to analyze the mycoflora and potential mycotoxin contamination of soil and corn samples collected at different plant maturity stages in Cap?o Bonito and Ribeir?o Preto, two regions of the State of S?o Paulo, Brazil. In addition, the data obtained were correlated with the occurrence of wind-dispersed fungi and the predominant climatic conditions of the two regions studied. Corn mycoflora profiles showed that Fusarium verticillioides prevailed in 35% of the samples from Cap?o Bonito and in 49% of the samples from Ribeir?o Preto. Examination of wind-dispersed fungi also revealed a high incidence of F. verticillioides. Soil mycoflora analyses showed that Penicilliumwas the most prevalent genus, although F. verticillioides was present in 55.5% of Cap?o Bonito's samples and in 26.7% of Ribeir?o Preto's samples. With respect to water activity, the corn kernels most contaminated with F. verticillioides had water activity levels of 0.70-0.80. HPLC analysis of fumonisins revealed that 88.5% of Cap?o Bonito's kernels were contaminated with fumonisin B(1) (FB(1)) (0.09-10.87 microg/g) and 53.8% with fumonisin B(2) (FB(2)) (0.05-0.52 microg/g); Ribeir?o Preto's kernels presented contamination levels of 93.5% for FB(1) (0.11-17.69 microg/g) and 61.3% for FB(2) (0.05-5.24 microg/g). No aflatoxins were detected by thin-layer chromatography in corn grains of either region. The concomitant occurrence of F. verticillioides and fumonisins in most of the field corn assayed demonstrates the importance of an effective control of cultivation throughout the plant maturity stages.     

Effect of industrial processing on the distribution of aflatoxins and zearalenone in corn-milling fractions

The aim of this study was to investigate the distribution of aflatoxins and zearalenone levels in various corn-milling fractions. Corn kernels and six derived milling fractions (germ, bran, large and small grits, flour, and animal feed flour) were sampled in an industrial plant; both conventional and organic corns were sampled. To evaluate the effect of cooking, samples of polenta were prepared starting from naturally contaminated flour. Conventional and organic lots showed mycotoxin contamination. For both lots, germ, bran, and animal feed flour showed a marked concentration factor from 239 to 911% accounting for both the low yields of the derived products and the distribution of aflatoxins and zearalenone contamination in the outer parts of the kernels. Conversely, a reduction factor of at least four times from raw material to finished products was observed. Polenta samples were unaffected by the cooking process, with levels of contamination similar to those of starting flour.     

Liquid chromatographic method for determination of aflatoxins B1, B2, G1, and G2 in corn and peanut products: collaborative study

A collaborative study of a liquid chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, Canada, South Africa, and Switzerland. Twenty-one artificially contaminated raw peanuts, peanut butter, and corn samples containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The test portion was extracted with methanol-0.1N HCl (4 + 1), filtered, defatted with hexane, and then partitioned with methylene chloride. The concentrated extract was passed through a silica gel column. Aflatoxins B1 and G1 were derivatized with trifluoroacetic acid, and the individual aflatoxins were determined by reverse-phase liquid chromatography with fluorescence detection. Statistical analysis of the data was performed to determine or confirm outliers, and to compute repeatability and reproducibility of the method. For corn, relative standard deviations for repeatability (RSDr) for aflatoxin B1 ranged from 27.2 to 8.3% for contamination levels from 5 through 50 ng/g. For raw peanuts and peanut butter, RSDr values for aflatoxin B1 were 35.0 to 41.2% and 11.2 to 19.1%, respectively, for contamination levels from 5 through 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. Relative standard deviations for reproducibility (RSDr) for aflatoxin B1 ranged from 15.8 to 38.4%, 24.4 to 33.4%, and 43.9 to 54.0% for corn, peanut butter, and raw peanuts, respectively. The method has been adopted official first action for the determination of aflatoxins B1, B2, G1, and G2 in peanut butter and corn at concentrations greater than or equal to 13 ng total aflatoxins/g.     

Aflatoxins and fumonisins in corn from the high-incidence area for human hepatocellular carcinoma in Guangxi, China

A comparative study on the natural occurrence of aflatoxins and Fusarium toxins was conducted with corn samples from high- and low-incidence areas for human primary hepatocellular carcinoma (PHC) in Guangxi, China. In samples from the high-risk area, aflatoxin B(1) was the predominant toxin detected in terms of quantity and frequency, with its concentration ranging between 9 and 2496 microg/kg and an 85% incidence of contamination. Among the samples, 13 (76%) exceeded the Chinese regulation of 20 microg/kg for aflatoxin B(1) in corn and corn-based products intended for human consumption. Significant differences in aflatoxin B(1), B(2), and G(1) and total aflatoxin concentrations in corn between the areas were found (P < 0.05). The average daily intake of aflatoxin B(1) from corn in the high-risk area was 184.1 microg, and the probable daily intake is estimated to be 3.68 microg/kg of body weight/day, 3.20 times the TD(50) in rats. Corn samples from both areas were simultaneously contaminated with fumonisins B(1), B(2), and B(3). Aflatoxin B(1) may play an important role in the development of PHC in Guangxi.     

Mycoflora Distribution in Dry‐Milled Fractions of Corn in Argentina

Corn samples and different commercial dry‐milled fractions collected from an industrial mill in Argentina were surveyed for fungal contamination. The percentage of Fusarium isolates in whole corn kernels among all fungi recovered was 2.0–97.0%; in corn grits, it was 2.6–50.0%. Maximum levels in the other fractions were 5.2 × 10⁵ colony forming units per gram (CFU/g) in germ and bran, 5.0 × 10³ CFU/g in C flour, and 2.7 × 10³ CFU/g in corn meal. The high initial contamination from whole corn is reflected in germ and bran, which is destined for animal consumption, but not in corn meal. F. verticillioides and Aspergillus flavus were the most frequent species in the whole corn kernel, but F. verticillioides was prevalent in all the other industrial fractions. Other potentially toxigenic fungi that were isolated included Aspergillus parasiticus, Alternaria alternata, Penicillium citrinum, and P. funiculosum. In this first report about mold contamination in corn industrial dry‐milled fractions in Argentina, the high fungal contamination level observed in the stored corn could indicate the necessity to improve the hybrid quality and the storage conditions to diminish the risk of mycotoxin occurrence.     

Incidence of Fusarium verticillioides and levels of fumonisins in corn from main production areas in Iran

A total of 52 corn samples collected in 2000 from four main corn production provinces of Iran (Fars, Kermanshah, Khuzestan, and Mazandaran) were analyzed for contamination with Fusarium verticillioides and fumonisins (FB(1), FB(2), FB(3), and 3-epi-FB(3)). The mean incidence of F. verticillioides (percent of kernels infected) for these four areas was 26.7, 21.4, 24.9, and 59.0%, respectively. The incidence in Mazandaran was significantly (p < 0.05) above that of the other areas. All samples from Mazandaran were contaminated with fumonisins with a mean level of total fumonisins of 10674 microg/kg. In contrast, the incidence of fumonisin contamination above 10 microg/kg was 53 (8/15), 42 (5/12), and 57% (8/14) in the samples from Fars, Kermanshah, and Khuzestan, respectively, and the corresponding mean total fumonisin levels were 215, 71, and 174 microg/kg, respectively. No statistical differences (p > 0.05) were observed in the fumonisin levels of the corn samples from these three provinces, which were significantly (p < 0.05) lower than the fumonisin contamination in samples from Mazandaran.     

An analytical survey of aflatoxins in tissues from swine grown in regions reporting 1988 aflatoxin-contaminated corn.

A joint project was undertaken by the Food Safety and Inspection Service (FSIS) and the Agriculture Research Service branches of the U.S. Department of Agriculture to determine the presence of aflatoxins in the U.S. meat supply during a drought year. In 1988, high incidences of aflatoxins occurred in corn grown in regions of the Midwest, Southeast, and South. Six states were identified as having serious aflatoxin contamination in their corn crop: Virginia, North and South Carolina, Texas, Iowa, and Illinois. Swine liver and pillars of diaphragm (muscle) tissues were sampled by federal FSIS Inspectors in plants located in these states. A worstcase sampling plan was conducted. Samples were taken in January 1989 from hogs fed corn soon after harvest and in April 1989 from hogs fed corn originally stored and then fed in the spring. A modification of the official AOAC method for the thin-layer chromatography (TLC) determination of aflatoxins in animal tissue was used to permit quantitation by LC with fluorescence detection. The official AOAC TLC confirmation of identity method was used to confirm all positive samples with B1 concentrations greater than 0.04 ppb and M1 concentrations greater than 0.1 ppb. Sixty samples in the January group and 100 samples in the April group were assayed. Concentrations of aflatoxins B1 and M1 in the first group of pig livers ranged from 0.04 to 0.06 ppb. The identity of aflatoxin B1 was confirmed in all positive samples. Aflatoxin M1 could not be confirmed in any of the positive liver samples because the method was insufficiently sensitive for this aflatoxin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survey of aflatoxins, ochratoxin A, zearalenone, and sterigmatocystin in some Brazilian foods by using multi-toxin thin-layer chromatographic method

A previously published method for ochratoxin A was evaluated and proved appropriate for simultaneous determination of aflatoxins, ochratoxin A, sterigmatocystin, and zearalenone, with considerable savings in time and reagent costs. The detection limits were 2, 5, 15, and 55 micrograms/kg, respectively. The recoveries and coefficients of variation obtained with artificially contaminated samples were 91-101% and 0-16% for aflatoxin B1, 98-117% and 0-17% for sterigmatocystin, and 96-107% and 0-17% for zearalenone, respectively. The coefficients of variation for naturally contaminated samples (aflatoxins in rice and ochratoxin A in beans) ranged from 0 to 8%. The method was used to survey 296 samples that included 10 cultivars of dried beans, 8 types of corn products, 3 types of cassava flour, and both polished and parboiled rice between May 1985 and June 1986 in Campinas, Brazil. Only aflatoxin B1 (9 samples, 20-52 micrograms/kg), aflatoxin G1 (4 samples, 18-31 micrograms/kg), and ochratoxin A (5 samples, 32-160 micrograms/kg) were found. The average contamination percentage was 4.7%; beans showed the highest (6.6%) and rice showed the lowest (3.3%) incidence rates. Zearalenone and sterigmatocystin were not detected. Positive samples were confirmed by chemical derivatization, corroborated by development in 3 solvent systems.     

Influence of Kernel Damage on Corn Nutrient Composition,Dry Matter Losses,and Processability During Alkaline Cooking

The nutrient losses of corn containing 0–30% damaged kernels that occurred during alkaline cooking into tortillas were examined. Samples from different stages during processing were tested for chemical composition and protein fractionation. The most prevalent type of kernel damage was mechanical, followed in decreasing order by molds, insects, heat, and rodent damage. Corn with higher content of damaged kernels was susceptible to overcooking, resulting in cracked or fully open nixtamal kernels and sticky masa that were difficult to handle during processing. Nutrient losses increased with increasing levels of kernel damage. Most nutrient losses from sound corn kernels occurred during washing as the pericarp and attached solids were removed. During simmering, damaged corn kernels were fully cooked into physically opened kernels with more nutrients being extracted into the water. About 15% of total solids and 50% of both crude fiber and fat were lost during cooking of corn with 30% kernel damage. The greatest losses were consistently observed for albumins and globulins from both sound and damaged kernels at all stages of cooking. Appropriate control of kernel damage level is required to improve yield of product with consistent quality. The susceptibility to overcooking of excessively damaged corn increases the complexity to consistently meet product quality specifications. Excess dry matter losses in the cooking liquor can significantly increase the risk of environmental contamination and cost of sewage water treatment.     

Dynamics of mycotoxin and Aspergillus flavus levels in aging Bt and non-Bt corn residues under Mississippi no-till conditions

Mycotoxin and Aspergillus flavus levels in soil-surface corn debris left by no-till agriculture methods (stover, cobs, and cobs with grain) were determined during the December-March fallow period for near-isogenic Bt and non-Bt hybrid corn. By December, average mycotoxin levels in non-Bt corn were many times higher in cobs with grain than in grain harvested in September (total aflatoxins, 774 vs 211 ng/g; total fumonisins, 216 vs 3.5 microg/g; cyclopiazonic acid, 4102 vs 72.2 microg/g; zearalenone, 0.2 vs < 0.1 microg/g). No trichothecenes were detected. Levels of mycotoxins and A. flavus propagules were approximately 10- to 50-fold lower in cobs without grain and stover, respectively, for all mycotoxins except zearalenone. Mycotoxin levels in corn debris fractions decreased during winter but began to rise in March. Levels of all mycotoxins and A. flavus propagules were lower in harvested grain and debris from Bt than non-Bt corn, but differences were significant (p < 0.05) only for aflatoxins.     

Reduction of Aflatoxin and Fumonisin Contamination in Yellow Corn by High‐Speed Dual‐Wavelength Sorting

A high‐speed dual‐wavelength sorter was tested for removing corn contaminated in the field with aflatoxin and fumonisin. To achieve accurate sorting, single kernel reflectance spectra (500–1,700 nm) were analyzed to select the optimal pair of optical filters to detect mycotoxin‐contaminated corn during high‐speed sorting. A routine, based on discriminant analysis, was developed to select the two absorbance bands in the spectra that would give the greatest classification accuracy. In a laboratory setting, and with the kernels stationary, absorbances at 750 and 1,200 nm could correctly identify >99% of the kernels as aflatoxin‐contaminated (>100 ppb) or uncontaminated. A high‐speed sorter was tested using the selected filter pair for corn samples inoculated with Aspergillus flavus; naturally infested corn grown in central Illinois; and naturally infested, commercially grown and harvested corn from eastern Kansas (2002 harvest). For the Kansas corn, the sorter was able to reduce aflatoxin levels by 81% from an initial average of 53 ppb, while fumonisin levels in the same grain samples were reduced an average of 85% from an initial level of 17 ppm. Similar reductions in mycotoxin levels were observed after high‐speed sorting of A. flavus inoculated and naturally mold‐infested corn grown in Illinois.     

Evaluation of enzyme-linked immunosorbent assay of cleanup for thin-layer chromatography of aflatoxin B1 in corn, peanuts, and peanut butter

A simple, rapid enzyme-linked immunoassay (ELISA) was used to evaluate the performance of each step (extraction, filtration, solvent partition, and silica gel column chromatography) of a solvent-efficient thin-layer chromatographic (TLC) method which is undergoing interlaboratory collaborative study for the determination of aflatoxin B1 in corn, raw peanuts, and peanut butter. The apparent average recoveries using the ELISA method were about 30 to 50% higher than those using the TLC method if only the amount of B1 added to the samples was used in the calculations. After the cross-reaction of the antibody with other aflatoxins added to the samples was considered, the amounts recovered approached the levels of aflatoxins added in all 3 commodities tested. With no cleanup treatment, ELISA recoveries at aflatoxin B1 levels above 7.5 ng/g were 84, 79, and 103% for corn, raw peanuts, and peanut butter, respectively. The coefficients of variation were between 5.2 and 25.2%. With each cleanup step in the TLC method, ELISA detected a progressive decrease in recovery from 150.5 to 105.3% (before correction for the presence of other aflatoxins) or from 93.5 to 65.4% (after correction for other aflatoxins) of B1 added to the samples. The ELISA data support the conclusion obtained from previous studies that cleanup treatments were not necessary in the ELISA. When large amounts of other aflatoxins are present, an understanding of the cross-reactivity of antibody with other aflatoxins in the ELISA is essential for final interpretation of the data.     

Enzyme-linked immunosorbent assay for screening aflatoxin B1 in cottonseed products and mixed feed: collaborative study

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, South Africa, Switzerland, The Netherlands, Tunisia, and the United States. Twenty-eight samples of raw and roasted peanuts, corn, whole cottonseed, cottonseed meal, ammoniated cottonseed meal, and poultry feed containing various quantities of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on conjugation of pure aflatoxin B1 to an enzyme and the competition between this conjugate and (free) aflatoxins in the product for aflatoxin-specific antibodies coated onto microtiter well walls. After a wash step to remove all unbound aflatoxins, a substrate, added to each well, is catalyzed from a colorless to a green solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the product increases. Overall correlation was good between ELISA and thin-layer chromatographic (TLC) results for cottonseed products and mixed feed. Variable results were reported for corn and peanut product samples. Although some positive samples (greater than 15 ng/g) of cottonseed products and mixed feed were reported to contain less than 15 ng/g by visual determination, a review of data for absorbance measurements showed that the contamination level was close to the greater than or equal to 15 ng/g standard and would not have been reported as negative under routine screening.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Aflatoxin B1 on Dry‐Grind Ethanol Process

Aflatoxins, like all mycotoxins, are toxic fungal metabolites that can have adverse health effects on animals and human beings. Aflatoxins are a major concern for the dry‐grind corn processing industry as it is believed that aflatoxins affect yeast and reduce its efficacy in producing ethanol. In the present study, aflatoxin B1 (100, 200, 350, or 775 ppb) was added to mycotoxin‐free corn and laboratory‐scale fermentations were conducted. No effect of aflatoxin B1 was observed on the fermentation rates or final ethanol concentrations. Mean ethanol concentration in the fermenter was 14.01–14.51% (v/v) at 60 hr for all the treatments. In the dry‐grind ethanol process, 55% of aflatoxin B1 was detected in wet grains and 45% in thin stillage.     

Liquid chromatographic determination and stability of the Fusarium mycotoxin moniliformin in cereal grains

Moniliformin is a mycotoxin produced by Fusarium subglutinans and other Fusarium species. A rapid, liquid chromatographic method for its determination in corn and wheat is described. Samples are extracted in acetonitrile-water (95 + 5); following defatting with n-hexane, an aliquot of the extract is evaporated and cleaned up on small C18 and neutral alumina columns successively. Reverse-phase liquid chromatography (LC) is conducted on a C18 column with 10 or 15% methanol or acetonitrile in aqueous ion-pair reagent as mobile phase, with detection by ultraviolet absorption at 229 and 254 nm. Average recoveries of moniliformin (potassium salt) added to ground corn and wheat at levels of 0.05-1.0 micrograms/g were 80% (n = 20) and 85% (n = 12), respectively, and the limit of detection was ca 0.01-0.18 micrograms/g, depending on LC conditions. Analysis of 24 samples of wheat, 4 samples of rye, and 12 samples of corn showed moniliformin in only 2 corn samples (0.06 and 0.2 micrograms/g). Moniliformin was also detected in a sample of artificially damaged (slashed) corn (0.2 micrograms/g) and selected kernels of corn that were field-inoculated with F. subglutinans and F. moniliforme (50 micrograms/g and 0.5 micrograms/g, respectively). In stability studies, moniliformin (potassium salt, 1 microgram/g) in ground corn and ground wheat heated at 50, 100, and 150 degrees C for 0.5-2 h decomposed moderately, e.g., 55% remained in corn after 0.5 h at 100 degrees C.     

Collaborative study of a screening method for the detection of aflatoxins in mixed feeds, other agricultural products, and foods.

A screening method for aflatoxins was collaboratively tested on 11 different agricultural and food products: white and yellow corn, peanuts, peanut butter, pistachio nuts, peanut meal, cottonseed meal, chicken, pig, and turkey starter rations, and dairy cattle feed. The method involves a rapid extraction and cleanup procedure followed by the detection of total aflatoxins (B1 + B2 + G1 + G2) as a fluorescent band on the Florisil layer of a Velasco-type minicolumn. The results of 32 collaborators from 10 different countries are presented. Samples containing 0, 5, 10, 15, 20, and 25 mug aflatoxins/kg were analyzed. Eighty-four per cent of the negative samples and 89% of the samples containing 10-25 mug total aflatoxins/kg were correctly identified. This method has been adopted as official first action for the detection of aflatoxins in corn, peanuts, peanut butter, peanut meal, cottonseed meal, mixed feeds, and pistachio nuts.     

Enzyme-linked immunosorbent assay of aflatoxins B1, B2, and G1 in corn, cottonseed, peanuts, peanut butter, and poultry feed: collaborative study

A direct competitive enzyme-linked immunosorbent assay (ELISA) screening method for aflatoxins at 20 ng/g was studied by 12 collaborators. Test samples of peanut butter were extracted by blending with methanol-water-hexane (55 + 45 + 100) and heating the test extracts on a steam bath; test samples of the other commodities were extracted by blending with methanol-water (80 + 20). All test extracts were filtered and the filtrates were diluted with buffer to a final methanol concentration of less than 30%. Each diluted filtrate was applied to a cup containing a filter with immobilized polyclonal antibodies specific to aflatoxins B1, B2, and G1. Aflatoxin B1-peroxidase conjugate was added, the cup was washed with water, and a mixture of hydrogen peroxide and tetramethylbenzidine was added. The test sample was judged to contain greater than or equal to 20 ng aflatoxins/g when, after exactly 1 min, no color was observed on the filter; when a blue or gray color developed, the test sample was judged to contain less than 20 ng aflatoxins/g. All collaborators correctly identified naturally contaminated corn and raw peanut positive test samples. No false positives were found for controls containing less than 2 ng aflatoxins/g. The correct responses for positive test samples spiked at levels of 10, 20, and greater than or equal to 30 ng aflatoxins/g (the ratio of B1:B2:G1 was 10:1:3) were 52, 86, and 96%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of two immunochemical methods with thin-layer chromatographic methods for determination of aflatoxins

Three different methods were compared for the determination of total flatoxins in corn and peanuts naturally contaminated with aflatoxins and in corn, peanuts, cottonseed, peanut butter, and poultry feed spiked with aflatoxins B1, B2, and G1. The 3 methods were an enzyme-linked immunosorbent assay (ELISA) screening test; a monoclonal antibody-affinity column-solid-phase separation method; and the AOAC official thin-layer chromatography (TLC) methods for all except poultry feed, for which Shannon's TLC method for mixed feed was used. The ELISA test is designed to provide only positive results for total aflatoxins at greater than or equal to 20 ng/g or negative results at less than 20 ng/g. The affinity column separation is coupled with either bromination solution fluorometry to estimate total aflatoxins or liquid chromatography (LC) to quantitate individual aflatoxins. Fluorodensitometry was used to determine aflatoxins in commodities analyzed by the TLC methods. The LC and TLC results were in good agreement for all the analyses. The results for the affinity column using bromination solution fluorometry were similar except those for cottonseed, which were about 60% higher. The ELISA screening method correctly identified naturally contaminated corn and peanut positive samples. No false positives were found for controls. The correct response for spiked corn, raw peanuts, peanut butter, and cottonseed at greater than or equal to 20 ng aflatoxins/g was about 90%. The correct response for spiked poultry feed at greater than or equal to 20 ng aflatoxins/g was about 50%.