Effect of tortilla-preparation process on aflatoxins B1 and B2 in corn

Naturally contaminated corn containing 450 and 54 ppb aflatoxins Bi and B2, respectively was treated with Ca(OH)₂ for making tortillas. The cleaned corn and tortillas were analyzed for aflatoxins B1 and B2 by high performance liquid chromatography (HPLC) and confirmed by thin layer chromatography (TLC). The average concentrations of aflatoxins B1 and B2 in the final products (tortillas) were only 40% and 28% lower than that in starting materials (corn kernels), respectively. Aflatoxins G1 and G2 were not detected in either corn or tortilla samples.     

Determination of mycobiota and mycotoxins in pig feed in central Argentina

Aims: To evaluate the mycobiota and natural levels of aflatoxins, fumonisins and zearalenone present in compound feed and home‐corn grains intended for fattening pigs. Methods and Results: Total fungi, Fusarium and Aspergillus species occurrence were examined. Aflatoxins and zearalenone were detected by thin‐layer chromatography and fumonisins by high‐pressure liquid chromatography. Fungal counts were generally higher than 1 × 10⁵ colony forming units (CFU) ml^?1. Aspergillus flavus, Aspergillus parasiticus and Fusarium verticillioides were the most prevalent species. FB₁ and FB₂ were detected in all feed and corn samples. Aflatoxin B₁ was detected in 33·33% of initial and growing feed and in 44·44% of final feed samples. It was not detected in corn samples. All feed and corn samples were negative for AFB₂, AFG₁, AFG₂ and ZEA presence during all growing stages tested. Conclusions: Fungal counts at all growing periods exceeded the levels proposed as feed hygienic quality limits. Aflatoxin levels in all feeds and fumonisin levels in many samples were higher than the established regulations. Significance and Impact of the Study: The presence of mycotoxins indicates the existence of contamination. This fact requires periodic monitoring to prevent the occurrence of mycotoxicosis in animal production, to reduce the economic losses and to minimize hazards to human health.     

Incidence of aflatoxins and aflatoxin producing fungi in animal feedstuffs

Fifty four samples including 5 of broken rice, 8 of corn grains, 8 of corn gluten feed, 13 of cottonseed cake and 4 each of rice polish, corn gluten, sesame oil cake, guar meal and wheat bran were screened for the presence of aflatoxins. Among all the samples, 14 were damaged and 40 apparently undamaged. The incidende of aflatoxins was found to be 60, 25, 25, and 23 per cent in broken rice, corn grains, corn gluten feed and cottonseed cake. Aflatoxins were not detected from rice polish, corn gluten, sesame oil cake, guar meal and wheat bran. Damaged sample revealed a much higher incidence i.e. 50 per cent as compared to undamaged ones i.e. 7.5 per cent. Mean concentration of aflatoxin B and G was found to be 15.5 and 12.2 ppb respectively.Cultural examination of aflatoxin positive feedstuffs yielded 39 isolates of different fungi including 21 of Aspergillus, 7 of Mucor, 6 of Rhizopus, 4 of Fusarium and one of Penicillium. These strains when tested for aflatoxin producing ability, revealed this property in only one isolate, identified as Aspergillus parasiticus.     

A limited survey of aflatoxins and fumonisins in retail maizebased products in the UK using immunoassay detection

A total of 27 maize-based products destined for human consumption were collected from retail outlets within the city of Glasgow in the UK and were analysed for the presence of aflatoxins using immunoaftinity column chromatography with fluorescence detection and for fumonisins by competitive ELISA. Aflatoxins were detected at a trace level below 4 in eight (30%) of the 27 samples tested, no sample contained aflatoxins at a high level although one sample of sweetcorn did contain aflatoxins at a level of 5-10 Fumonisins were detected in eight (30%) of the samples at levels from 1 to 8mgkg^-1 and a further eight samples contained fumonisin at a level below 1 mgkg^-1 but above the detectable level. The highest concentration of fumonisins was found in a sample of fine corn meal at 8-12mgkg^-1.     

Natural occurrence of aflatoxins,deoxynivalenol, fumonisins and zearalenone in maize from Entre Ríos Province,Argentina

In Entre Ríos, Argentina, corn is one of the most important cereal grains produced, being an important income for the regional economy. The aim of this work was to assess aflatoxins, zearalenone, deoxynivalenol (DON) and fumonisins (FB) in corn harvest in 2003 and 2004 in the most contaminated departments found in previous studies in selected sampling places. At the harvest time, when the trucks arrived to store plants, samples of corn were taken from seven different positions of the trucks and from five in the trailer. Composite samples were randomised reduced to 10 kg. The samples were analysed by immunological tests, by thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and/or gas liquid chromatography-electron capture detector (GLC-ECD). In 2003 average contamination was 3.19 u.g/kg for aflatoxins, 118.5 μg/kg for deoxynivalenol, 230.8 μg/kg for zearalenone and 10200 μg/kg of total fumonisins (HPLC and ELISA quantification showed a linear correlation (r² =0.9618), but RIDASCREEN®FAST values were 1.7 higher than HPLC values); in 2004 deoxynivalenol and zearalenone were not detected and an average of 2.0 μg/kg for aflatoxins and 4700 μg/kg for total fumonisins was found.This province, with the earliest harvested corn in the country each summer, tends to display different contaminations from the rest of the provinces, probably due to climate characteristics, particularly hotter weather.     

Mycobiota and mycotoxins in fermented feed,wheat grains and corn grains in Southeastern Buenos Aires Province,Argentina

Wheat (as bran) and corn (as dry grain or fermented feed) are main ingredients of feedstuffs used in local cattle and pig farms in the South of the Buenos Aires Province (Argentina). Therefore, determining mycobiota and mycotoxins in wheat and corn is of prime importance for developing feed management techniques to optimise animal production and to minimize toxicity. Then, a mycological survey was carried out in the Southeastern part of the Buenos Aires Province, in order to identify the mycobiota and the main mycotoxins present in fermented feed, wheat grain and corn grain samples. Samples were cultured for fungal quantification, isolation and identification, and analysed for deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin and aflatoxins (AFLA). Penicillium (74%), Aspergillus (32%) and Scopulariopsis (21%) were the prevalent genera in fermented feed. Penicillium (70%), Fusarium (47%) and Aspergillus (34%) were the most frequent fungi isolated from corn. Penicillium (42%), Fusarium (27%) and Alternaria (25%) were the most frequently recovered genera from wheat. DON was detected in 59% of the corn samples, in 45% of the wheat samples and in 38% of the silage samples. ZEA was detected in 36% of the corn samples, in 49% of the wheat samples and in 16% of the silage samples. T-2 toxin and aflatoxin B1 were each detected in 4% of the corn samples. Eighteen percent of the fermented feed samples showed T-2 contamination. Fermented feed and wheat samples were negative for AFLA.     

Natural occurrence of aflatoxins and ochratoxin a in corn and barley from mazandaran and golestan in north provinces of I. R. Iran

Fourteen barley and nine corn samples, destined for animal feed, collected from Golestan and Mazandaran provinces in the north of Islamic Republic of Iran (I. R. Iran) were analysed for aflatoxins (AF) and ochratoxin A (OA) by high performance liquid chromatography. In corn samples, aflatoxin B₁ (AFB₁) and aflatoxin B₂ (AFB₂) were detected in 8 (88.8%) and 6 (66.6%) samples at a mean level of 15.83 and 2.99 ppb (median 1.72 and 1 ppb), respectively. None of the corn samples contained detectable amounts of aflatoxin G₁ (AFG₁) and aflatoxin G₂ (AFG₂). Only one of the AF-contaminated samples was co-contaminated with OA at a concentration of 0.35 ppb. This is the first report concerning natural occurrence of OA and co-occurrence with AF in corn samples of north of I. R. Iran.     

Ear-rot fungi and mycotoxins in South African corn of the 1989 crop exported to Taiwan

A shipment of South African corn (1989) exported to Taiwan, was analyzed for various ear-rot fungi andFusarium mycotoxins. Two sets of samples, one from the points of origin in South Africa prior to shipment, and the other from the end-point distributors in Taiwan, were studied. Surface-sterilized kernels were plated onto two different agar media and the fungal colonies identified. High Performance Liquid Chromatography was used to analyze mycotoxin levels. The predominant ear-rot fungi, in decreasing order of isolation frequency, wereFusarium subglutinans, F. moniliforme, Diplodia maydis andF. graminearum. Aspergillus flavus andA. parasiticus were not isolated from samples prior to export, but a small number ofA. flavus isolates were found after shipment. The predominant mycotoxins were fumonisins B₁ (0–865 ng/g) and B₂ (0–250 ng/g). Low levels of moniliformin (390 ng/g) were detected in some samples before shipment. Zearalenone (25 ng/g), and nivalenol (120 ng/g) were detected in two out of 32 samples taken in Taiwan. The samples contained no detectable levels of either aflatoxins (>0.5 ng/g) or deoxynivalenol (>100 ng/g) before or after shipment.Abbreviations RSA South Africa(n) - FB₁ fumonisin B₁ - FB₂ fumonisin B₂ - ETVL eastern Transvaal - WTVL western Transvaal     

Production of fumonisin B1 and B2 byFusarium moniliforme isolated from Korean corn kerneis for feed

The natural occurrence of fumonisin B₁ (FB₁) and B₂ (FB₂), a promoter for hepatocarcinogenesis, was investigated in Korean corn kernels for feed by HPLC with fluorescence detection. From the 12 corn kernel samples, FB₁ was detected in 5 samples at levels ranging from 53 to 1327ng/g, while FB₂ was found in 4 samples from 69 to 680ng/g. In the positive samples, the average concentrations of FB₁ and FB₂ were 506 and 288ng/g, respectively. One sample (No. K3) showed the highest FB₁ and FB₂ contents as 1327 and 680ng/g, respectively. In the micrological survey on 5 positive samples for FB₁ and FB₂, 6 strains ofFusarium monlliforme were isolated, and all these isolates had a producibility of FB₁ and FB₁, with maximum levels of 80.7 to 180.9 g/g.Thisis the first report on the natural co-contamination of FB₁ and FB₂ in Korean corn kernels for feed, and on the ability ofF. moniliforme isolated from corn kernels for feed in Korea to produce FB₁ and FB₂.     

Mycoflora,and mycotoxins production in Nigerian corn and corn-based snacks

Thirty-one fungal species, mostly toxigenic and belonging to 11 genera were isolated from corn, corn cake and corn roll snack samples.Aspergillus, Penicillum andFusarium accounted for 10, 6 and 3 of the species and altogether, they constituted 90, 94 and 88 percent of the total fungi in corn, corn cake and corn roll snack respectively. Mycotoxins (aflatoxins and ochratoxin A) were detected in 45, 80 and 12 percent while the means and ranges of the total aflatoxins recorded were: 200(25–770 ppb); 233(15–1070 ppb) and 55(10–160 ppb) for corn, corn cake and corn roll snack samples respectively. Ochratoxin A was detected at toxicologically significant levels in only 15 percent of the corn cake samples analyzed. All the strains ofAspergillus flavus andA. ochraceus tested produced aflatoxin B and ochratoxin A, respectively, when they were cultured on each of the three substrates. In each case, substantial quantities of the toxins were produced from 25 to 35°C with the peak level recorded at 30°C. Toxin production was detected only in substrates with 15 percent moisture content and above; reaching the maximum at 25 or 30 percent moisture level. No substantial differences in the amount of toxins were elaborated with further increase in substrates' moisture content. Of the three substrates, corn cake was the most suitable for aflatoxin B production while they were all equally suitable for the elaboration of ochratoxin A.     

A note on the screening of dried shrimps, shrimp paste and raw groundnut kernels for aflatoxin-producing Aspergillus flavus

S im , T.S., T eo , T heresa & S im , T.F. 1985. A note on the screening of dried shrimps, shrimp paste and raw groundnut kernels for aflatoxin-producing Aspergillus flavus. Journal of Applied Bacteriology 59 , 29–34.
All of 33 samples of dried shrimps, shrimp paste, peanut butter and raw groundnut kernels were contaminated with fungi. Aspergillus and Penicillium spp. were the predominant types in dried shrimps and raw groundnut kernels but no Aspergillus spp. were present in peanut butter or shrimp paste samples. Among 81 Aspergillus isolates obtained from dried shrimps and raw groundnut kernels, 10 were A. flavus/ A. parasiticus , of which five were potential aflatoxin-producing A. flavus strains. No aflatoxins were detected in the food samples although some were visibly mouldy and some had high mould counts. The occurrence of aflatoxin-producing strains of A. flavus in dried shrimps and raw groundnut kernels warrants further investigation of these foods and their products as potentially significant sources of aflatoxins.     

Imaging and automated detection of Sitophilus oryzae (Coleoptera: Curculionidae) pupae in hard red winter wheat

Computed tomography, an imaging technique commonly used for diagnosing internal human health ailments, uses multiple x-rays and sophisticated software to recreate a cross-sectional representation of a subject. The use of this technique to image hard red winter wheat, Triticum aestivm L., samples infested with pupae of Sitophilus oryzae (L.) was investigated. A software program was developed to rapidly recognize and quantify the infested kernels. Samples were imaged in a 7.6-cm (o.d.) plastic tube containing 0, 50, or 100 infested kernels per kg of wheat. Interkernel spaces were filled with corn oil so as to increase the contrast between voids inside kernels and voids among kernels. Automated image processing, using a custom C language software program, was conducted separately on each 100 g portion of the prepared samples. The average detection accuracy in the five infested kernels per 100-g samples was 94.4 +/- 7.3% (mean +/- SD, n = 10), whereas the average detection accuracy in the 10 infested kernels per 100-g sample was 87.3 +/- 7.9% (n = 10). Detection accuracy in the 10 infested kernels per 100-g samples was slightly less than the five infested kernels per 100-g samples because of some infested kernels overlapping with each other or air bubbles in the oil. A mean of 1.2 +/- 0.9 (n = 10) bubbles (per tube) was incorrectly classed as infested kernels in replicates containing no infested kernels. In light of these positive results, future studies should be conducted using additional grains, insect species, and life stages.     

Survey of Vietnamese Peanuts,Corn and Soil for the Presence of <Emphasis Type="Italic">Aspergillus flavus</Emphasis> and <Emphasis Type="Italic">Aspergillus parasiticus</Emphasis>

Aspergillus flavus and Aspergillus parasiticus cause perennial infection of agriculturally important crops in tropical and subtropical areas. Invasion of crops by these fungi may result in contamination of food and feed by potent carcinogenic aflatoxins. Consumption of aflatoxin contaminated foods is a recognised risk factor for human hepatocellular carcinoma (HCC) and may contribute to the high incidence of HCC in Southeast Asia. This study conducted a survey of Vietnamese crops (peanuts and corn) and soil for the presence of aflatoxigenic fungi and used microsatellite markers to investigate the genetic diversity of Vietnamese Aspergillus strains. From a total of 85 samples comprising peanut (25), corn (45) and soil (15), 106 strains were isolated. Identification of strains by colony morphology and aflatoxin production found all Vietnamese strains to be A. flavus with no A. parasiticus isolated. A. flavus was present in 36.0% of peanut samples, 31.1% of corn samples, 27.3% of farmed soil samples and was not found in virgin soil samples. Twenty-five per cent of the strains produced aflatoxins. Microsatellite analysis revealed a high level of genetic diversity in the Vietnamese A. flavus population. Clustering, based on microsatellite genotype, was unrelated to aflatoxin production, geographic origin or substrate origin.     

Mycotoxins in laboratory rodent feed

Twenty-one batches of fixed-formula rodent diets from three feed manufacturers were tested for the presence of five mycotoxins: deoxynivalenol (DON), nivalenol (NIV), HT-2 toxin, T-2 toxin and ochratoxin A (OTA). Five batches were also tested for the presence of zearalenone (ZEN) and six batches for aflatoxins. Detectable levels of DON (up to 298 microg/kg), NIV (up to 118 microg/kg), OTA (up to 3.1 microg/kg) or ZEN (up to 26.7 microg/kg) were found in samples from all manufacturers. Three batches contained two (DON or NIV and OTA or ZEN) and one batch contained three (DON, OTA and ZEN) different mycotoxins. Aflatoxins, T-2 and HT-2 were not detected in any of the batches. The concentrations of mycotoxins detected in the feed were low, but indicated that feed ingredients, probably the cereal ingredients, were contaminated by mycotoxins. Since mycotoxins are known to have toxic and/or immunosuppressive effects, non-contaminated ingredients should be used for production of laboratory animal feed. The results imply that an improved quality control of ingredients used for laboratory rodent feed should be implemented.     

Preharvest aflatoxin contamination: effect of moisture and substrate variation in developing cottonseed and corn kernels.

Variations in moisture and substrate in preharvest corn kernels and cottonseed were linked with the ability of Aspergillus parasiticus to infect the seed and produce aflatoxin. Osmotic pressures and moisture content (MC) levels of developing starch-rich corn kernels and lipid-rich cottonseed were determined. For in vivo studies, corn kernels and cottonseed were inoculated with A. parasiticus conidia and retained on plants through maturation. For in vitro studies, samples of corn kernels and cottonseed were collected at various stages, sterilized, inoculated, incubated for 2 weeks, and assayed for toxin. Aflatoxin levels were highest in corn kernels inoculated at 28 days postflowering (52% MC) in both the in vivo and in vitro tests. Toxin concentrations in cottonseed were greatest with inoculation at 35 days postflowering (70% MC) in seed retained on the plant, but toxin accumulation continued to increase with the maturity of the seed inoculated in cottonseed used in the in vitro trials. Moisture and substrate conditions in the midrange of seed development provided optimum conditions for fungal development and toxin production in seed retained on the plant.     

Preharvest aflatoxin contamination: effect of moisture and substrate variation in developing cottonseed and corn kernels

Variations in moisture and substrate in preharvest corn kernels and cottonseed were linked with the ability of Aspergillus parasiticus to infect the seed and produce aflatoxin. Osmotic pressures and moisture content (MC) levels of developing starch-rich corn kernels and lipid-rich cottonseed were determined. For in vivo studies, corn kernels and cottonseed were inoculated with A. parasiticus conidia and retained on plants through maturation. For in vitro studies, samples of corn kernels and cottonseed were collected at various stages, sterilized, inoculated, incubated for 2 weeks, and assayed for toxin. Aflatoxin levels were highest in corn kernels inoculated at 28 days postflowering (52% MC) in both the in vivo and in vitro tests. Toxin concentrations in cottonseed were greatest with inoculation at 35 days postflowering (70% MC) in seed retained on the plant, but toxin accumulation continued to increase with the maturity of the seed inoculated in cottonseed used in the in vitro trials. Moisture and substrate conditions in the midrange of seed development provided optimum conditions for fungal development and toxin production in seed retained on the plant.     

A note on the screening of dried shrimps, shrimp paste and raw groundnut kernels for aflatoxin-producing Aspergillus flavus

All of 33 samples of dried shrimps, shrimp paste, peanut butter and raw groundnut kernels were contaminated with fungi. Aspergillus and Penicillium spp. were the predominant types in dried shrimps and raw groundnut kernels but no Aspergillus spp. were present in peanut butter or shrimp paste samples. Among 81 Aspergillus isolates obtained from dried shrimps and raw groundnut kernels, 10 were A. flavus/A. parasiticus, of which five were potential aflatoxin-producing A. flavus strains. No aflatoxins were detected in the food samples although some were visibly mouldy and some had high mould counts. The occurrence of aflatoxin-producing strains of A. flavus in dried shrimps and raw groundnut kernels warrants further investigation of these foods and their products as potentially significant sources of aflatoxins.     

Natural occurrence of mycotoxins and mycoflora of argentinien popcorn

Argentina is the first popcorn exporting country worldwide. In 1997-1998 harvest season, 40,000 ha were sown with a production of 125,000 tons; 120,000 tons of this production were exported to more than 40 countries. The objectives of this study were to isolate and to identify the fungi present in this cereal and to assess the occurrence of mycotoxins in freshly harvested popcorn in Buenos Aires province, Argentina, in 1999. All popcorn samples showed fungal contamination. A total of 4,211 isolates were recovered from popcorn kernel samples. The prevalent species isolated wasFusarium verticillioides followed byPenicillium funiculosum, F. graminearum andAlternaria alternata. No aflatoxins, zearalenone, deoxynivalenol or ochratoxin A were detected in the 42 popcorn simples. All samples but one were contaminated with fumonisins (FB) in a range in ug/kg of (not detected-529) for FB₁; (not detected-216) for FB₂ and (not detected-103) for FB₃. Fumonisin contamination levels in Argentinean popcorn were lower than observed in flint corn. No significant differences in fungal and fumonisins contamination levels were observed in the different tested hybrids.     

Potential natural exposure of Mississippi sandhill cranes to aflatoxin B1.

A survey was conducted to determine if carcinogenic mycotoxins were present in foods consumed by Mississippi sandhill cranes (Grus canadensis pulla). Samples of field corn (Zea mays) (n = 111) and chufa (Cyperus esculentus) (n = 20), obtained in 1987, 1988 and 1989 on the Mississippi Sandhill Crane National Wildlife Refuge (MSCNWR) and nearby private lands were analyzed for aflatoxin B1(AB1), ochratoxin A and sterigmatocystin using thin layer chromatography. Chufa samples were negative for all three mycotoxins. Aflatoxin B1 was found in corn at concentrations from 5 to 5,000 ppb; the other mycotoxins were not found in corn. Contaminated corn was found in 72% of all corn fields, but the proportion of contaminated fields was 57 to 100% for the 3-yr period. Contamination with AB1 was greatest in corn obtained from the ground post-harvest. Overall, 32% of corn samples from the ground had levels greater than or equal to 200 ppb with a mean of 427 ppb (range = 5 to 5,000 ppb) in contaminated fields. In 1989, mean AB1 concentration in corn on the ground was 5 to 1138 ppb for individual fields. The concentration of AB1 was less than or equal to 200 ppb in all corn samples from upright stalks. The study demonstrated that AB1 is available to sandhill cranes and at levels that may pose a serious health threat.     

Fungi associated with post-harvest rot of black plum (Vitex doniana) in Nigeria

Groundnut samples from 21 selected markets in the 10 regions of Ghana yielded high levels of the aflatoxigenic fungus Aspergillus flavus on half-strength potato dextrose agar. The fungus was associated with 31.7 and 12.8%, respectively, of all damaged and undamaged kernels assayed. Only 0.24% of total kernels assayed yielded A. parasiticus. Other fungi detected from total kernels assayed were A. niger (34%), A. candidus (1.45%), A. tamarii (3.93%), A. ochraceous (5.26%), Fusarium spp. (1.7%) Penicillium spp. (5.19%), a Mucor sp. (2.3%), a Trichoderma sp. (0.2%), Rhizopus stolonifer (12%) and certain unidentifiable fungi (11.72%). Total aflatoxin levels ranging from 5.7 to 22, 168 ppb were identified with damaged kernel samples. The mycotoxin was not detected in 50% of undamaged kernel samples tested and very low levels mostly ranging from 0.1 to 12.2 ppb were associated with the undamaged samples that tested positive for aflatoxins. In a novel in vitro microbial assay to determine the effectiveness of certain plant extracts against aflatoxin synthesis, extracts from Xylopia aethiopica, Monodera myristica, Cinnamomum verum and Piper nigrum permitted fungal growth in 1.5% potato-dextrose broth while completely suppressing NOR formation. These extracts, however, could not suppress NOR formation in a yeast extract sucrose medium.