A field survey of pistachio (Pistacia vera) nut production and storage in Turkey with particular reference to aflatoxin contamination.

A field study of soils and pistachio nuts in three major pistachio-growing areas of Turkey has been undertaken. The predominant soil fungus isolated from all three areas was Aspergillus niger; isolates of Fusarium, Trichoderma, Mucor and Rhizopus species were also common. A flavus and A. ochraceus and related organisms were isolated only from the plateau of Gaziantep. The dominant external mycoflora of the immature nuts from all sites consisted of A. niger, A. flavus and Penicillium spp. There was no evidence for fungal contamination of immature endosperms nor of freshly dehulled nuts, but stored dehulled nuts and dust samples taken from ware-houses were extensively contaminated with A. flavus, A. niger and A. ochraceus. Of 43 A. flavus isolates tested, 20 produced aflatoxins on laboratory media or on rice; all 11 isolates of A. ochraceus tested produced ochratoxin A on laboratory media. The results obtained are discussed in relation to agricultural and marketing practices for Turkish pistachio nuts.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Mycotoxic flora and mycotoxins in smoke-dried fish from Sierra Leone

Examination of 20 samples of smoke-dried fish of the Ethmolosa sp. commonly called “Bonga”, from homes and markets in Njala (Sierra Leone) revealed the presence of 4 Aspergilli species: A. flavus Links ex Fries, A. ochraceus Wilhelm, A. tamarii Kita and A. niger van Tieghem. Fresh or properly preserved smoke-dried fish showed no signs of fungal contamination. Mouldy fish extracts contained varying amounts of aflatoxins B₁, G₁, G₂ and ochratoxin A. Isolates of A. flavus grown on yeast extract sucrose (YES) medium, produced considerable amounts of aflatoxin B₁ and G₁ and trace amounts of G₂. On YES medium A. ochraceus produced large amounts of ochratoxin A but no penicillic acid.     

Exploration of Islamic medicine plant extracts as powerful antifungals for the prevention of mycotoxigenic Aspergilli growth in organic silage

BACKGROUND: Feed contamination with mycotoxins is a major risk factor for animals and humans as several toxins can exist as residues in meat and milk products, giving rise to carry‐over to consumers via ingestion of foods of animal origin. The starting point for prevention, in this chain, is to eliminate the growth of mycotoxigenic fungi in the animal forage. Ten plant extracts, recommended in Islamic medicine, were evaluated as antifungal agents against mycotoxigenic Aspergilli, i.e. Aspergillus flavus and A. ochraceus, growth in organic maize silage. RESULTS: Most extracts had remarkable antifungal activities using both qualitative and quantitative evaluation methods. Cress (Lepidium sativum) seed extract was proven to be the most powerful among the plants examined. Blending of the most effective extracts (garden cress seed, pomegranate peel and olive leaf extracts), individually at their minimal fungicidal concentrations, with maize silage resulted in the reduction of inoculated A. flavus colony counts by 99.9, 99.6 and 98.7%, respectively, whereas silage blending with the combined extracts completely prohibited fungal growth for up to 30 days of incubation under aerobic conditions. CONCLUSION: Besides the health promoting effects, silage blending with the bioactive plant extracts examined could lead to the required protection from pathogenic and mycotoxigenic fungi. Copyright © 2011 Society of Chemical Industry     

Influence of white light,near-UV irradiation and other environmental conditions on production of aflatoxin B1 by Aspergillus flavus and ochratoxin A by Aspergillus ochraceus

The effects of illumination, near-ultraviolet, incubation temperature pH and some minor elements on the growth rate and production of aflatoxin B₁ by A. flavus and ochratoxin A by A. ochraceus were investigated. Aflatoxin B₁ and ochratoxin A production was considerably higher in the light than in the dark. The greatest aflatoxin B₁ and ochratoxin A production was occurred after 11 days of fermentation with light- and dark-grown cultures at 25 °C. The mycelial dry weight was also greater in the light than in the dark for both A. flavus and A. ochraceus. Exposure of conidia to near-UV irradiation increased mycelial dry weight and mycotoxins by both fungi more than white light. The greatest aflatoxin B₁ and ochratoxin A was at 25 °C with UV-grown culture (24 h exposure) producing a mean of 400 and 260 μg/50 ml of medium, respectively. The maximum aflatoxin B₁ and ochratoxin A yield was obtained at pH 5.5 and with increasing the initial pH to near neutrality, both mycotoxins yield decreased. Iron, cupper and zinc were observed to stimulate aflatoxin B₁ and ochratoxin A production and enhanced the growth rate of both A. flavus and A. ochraceus.     

Mycobiota of cocoa: from farm to chocolate

The present work was carried out to study the mycobiota of cocoa beans from farm to chocolate. Four hundred and ninety-four samples were analyzed at various stages of cocoa processing: (i) primary stage at the farm (fermentation, drying, and storage), (ii) secondary stage at processing (testa, nibs, liquor, butter, cake and powder) and (iii) the final chocolate product (dark, milk, white and powdered) collected from retail outlets. Direct plating or dilution plating on Dichloran 18% Glycerol agar were used for cocoa beans and processed product analyses, respectively. Fungi were isolated and identified using different keys of identification. The largest numbers and diversity of fungi were observed in the samples collected at the farm, especially during drying and storage. The species with the highest occurrence among samples were: Absidia corymbifera, Aspergillus sp. nov., A. flavus, Penicillium paneum and yeasts. A total of 1132 potentially toxigenic fungi were isolated from the following species or species groups: A. flavus, Aspergillus parasiticus, Aspergillus nomius, Aspergillus niger group, Aspergillus carbonarius and Aspergillus ochraceus group. The highest percentage of toxigenic fungi was found at the drying and storage stages. The industrial processing reduced the fungal contamination in all fractions and no fungi were found in the final chocolate products. The knowledge of which fungi are dominant at each processing stage of cocoa provides important data about their ecology. This understanding leads to a reduction in fungal spoilage and mycotoxin production in this product.     

Mycotoxin production by molds isolated from ‘Greek-style’ black olives

Seventeen mold strains were isolated from ‘Greek-style’ black olives produced in Morocco. Eight of these isolates were identified as Aspergillus flavus, seven as Aspergillus petrakii, and two as Aspergillus ocharaceus Wilhelm. The A. flavus strains were tested for production of aflatoxins B₁, B₂, G₁, and G₂; and A. ochraceus and A. petrakii strains were tested for production of ochratoxin, penicillic acid, patulin, and citrinin. The organisms were tested for mycotoxin production on five different substrates, including rice powder-corn steep agar, autoclaved rice, yeast-extract sucrose broth (YES), potato dextrose agar (PDA), and fresh olive paste. All strains of A. flavus produced aflatoxins on all substrates except olive paste and PDA. In PDA, only two strains produced Aflatoxin B₁. Five A. ochraceus group isolates produced penicillic acid on one or more of the substrates, but only two out of the five produced penicillic acid on olive paste. None produced ochratoxin, patulin or citrinin. Quantities of aflatoxin B₁ produced in rice ranged from 5 to 14 μg/g of rice, and of penicillic acid 15–32 μg/g of rice. In olive paste, the concentrations of penicillic acid were 11.4 and 30.2 μg/g. Biological toxicity of extracts of mold cultures was confirmed using chicken embryos and a microbiological test. Crude extracts of cultures were also tested for mutagenicity using the Salmonella mutagenicity (Ames) Test, and some gave positive mutagenic responses.     

Fungitoxic activity of Indian borage (Plectranthus amboinicus) volatiles

Indian borage (Plectranthus amboinicus) was investigated for antifungal activity through agar well diffusion assay. Indian borage oil (IBO) was found to be effective against various fungi tested, as it inhibited the radial growth of mycelia and exhibited broad fungitoxic properties against Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus CFR 221, Aspergillus oryzae, Candida versatilis, Fusarium sp. GF-1019, Penicillium sp., and Saccharomyces cerevisiae. The effective concentration of IBO on the growth of A. ochraceus in yeast extract sucrose medium was determined. IBO completely inhibited ochratoxin (OTA) production by the toxigenic strain A. ochraceus at 500 ppm. Also, the application of IBO at 100 mg/g in food samples resulted in inhibition of the growth of A. ochraceus in food systems such as groundnut, maize and poultry feed and no detectable amount of OTA was found at a high moisture level of 30%, even after seven days. IBO has the potential for use as a botanical fungitoxicant against fungal attack in stored food commodities.     

Sensitivity of Commercial Cheddar Cheese Starter Isolates to Bacteriophage Associated with Wheys

Seventy-six Cheddar cheese starter cultures were collected from five cheese plants located in New York, Wisconsin, and Illinois. Several single colony isolates from each starter culture were purified and identified to species on the basis of six biochemical reactions. Thirteen of the 76 starter cultures were identified as mixture of Strepcococcus lactis and S. cremoris and 63 of the starter cultures were single species. Plasmid profiles and resistance to five phages (ML3, C2, TRM, 18-16, and C5W6) were determined for all 450 isolates. One hundred and thirty-six isolates that constituted a representative cross-section of commercial strains were selected upon their plasmid and phage-resistance profiles. These strains were used as indicators to test phage activities of 57 wheys collected from four of the five cheese plants. Wheys from different cheese plants showed varying levels of phage activity. Wheys from the plant that had the most acute phage problem completely lysed at least 25% of the 136 strains. Most of the sensitive bacterial strains of the 136 isolates were lysed by wheys from two individual plants. The percentage of strains from each plant resistant to all 57 wheys ranged from 9 to 43.     

Cyclopiazonic acid and aflatoxin production by cultures of Aspergillus flavus isolated from dried beans and maize

From the storerooms of individual households 150 samples of dried beans and 90 samples of stored maize were collected for mycological analyses. Two of 27 isolates of A. flavus grown on malt extract agar (MEA) were found to produce the mycotoxin cyclopiazonic acid (25–36 μg/g). Three of the A. flavus isolates grown on crushed moist wheat produced aflatoxin B₁ (0.72–1.6 μg/g) and 6 of 26 A. ochraceus isolates were OA positive (0.5–10.4 μg/g). None of 25 bean samples were contaminated with CPA, AF or OA, while 4 samples of 30 tested maize samples were OA positive with level of OA 0.4–400 μg/g. Toxins were determined by thin layer chromatography and colorimetric method was used for quantitations of CPA.     

Production of aflatoxins in sausage,salami, sucuk and kavurma

Forty nine meat product samples were examined for the fungal genera. Penicillium sp. was detected in 74.8% of samples. No sample contained Aspergillus parasiticus or Aspergillus flavus. Production of aflatoxins in sausage, salami, sucuk and kavurma by A. parasiticus and A. flavus was studied at different temperatures. A. parasiticus and A. flavus produced no aflatoxins on meat products samples at 15°C. Sucuk was a poor substrate for A. parasiticus and A. flavus at 25°C. Sausage, salami and kavurma were favorable substrates for aflatoxin production by A. parasiticus at 25°C.     

Aspergillus species from section Flavi isolated from soil at planting and harvest time in peanut‐growing regions of Argentina

Aspergillus species from section Flavi were isolated from soil samples in three peanut‐growing regions of Córdoba Province, Argentina. The samples were collected during the planting and harvest periods. Both total fungal population and Aspergillus species from section Flavi showed no significant differences between planting and harvest time in two of the regions evaluated. Only in one region were there significant differences in cfu g^?1 of total fungal population and Aspergillus species from section Flavi. A flavus was the dominant species isolated in all three localities during the planting and harvest periods. There were significant differences (p < 0.05) in the ratio of toxigenic and atoxigenic strains dependent on the period and the region evaluated. In one region, higher frequencies of toxigenic A flavus and A parasiticus in soil were found and a high contamination level of aflatoxins was detected in peanut seeds. Copyright © 2003 Society of Chemical Industry     

Inhibitory effect of Aspergillus niger on the growth of Aspergillus ochraceus and Aspergillus flavus,and on aflatoxin formation

Aspergillus ochraceus and A flavus were grown on synthetic media (SM) supplemented with 50 or 200 ml litre^?1 SM on which A niger had been grown previously ( ‘A niger medium’ = ANM). Controls included SM acidified to pH 6.0 or 4.4, SM diluted with 50 or 200 ml litre^?1 water, and diluted-acidified SM. For both fungi, higher growth inhibition was recorded on ANM-containing SM than in the controls. Aflatoxin formation was markedly inhibited on SM to which 20 ml litre^?1 ANM extract (in methanol/chloroform, 2:1 v) had been added, although the growth of A flavus on that medium was almost the same as that in the control. It is concluded that the inhibitory effect of A niger on the growth of fungi should not be attributed merely to pH reduction, but also, mainly, to metabolites produced by the fungus in the growth medium, even at early stages of its growth.     

Evaluation of some essential oils as botanical fungitoxicants for the protection of stored food commodities from fungal infestation

Essential oils from different parts of 18 plants belonging to 11 families were extracted and tested against two toxigenic strains of Aspergillus flavus Link through the poisoned food technique. The oil of Mentha arvensis was found to be effective against both strains of A. flavus and completely stopped the radial mycelial growth of A. flavus at 0.10 mg mL^?1. It was found to be superior over the synthetic fungicides tested and showed a broad fungitoxic spectrum against A. niger, A. fumigatus, Botryodiplodia theobromae, Cladosporium cladosporioides, Fusarium oxysporum, Helminthosporium oryzae, Macrophomina phaseolina and Sclerotium rolfsii at 0.10 mg mL^?1. The oil completely inhibited the aflatoxin B1 production by the toxigenic strain of A. flavus at 0.05 mg mL^?1. Moreover, the Mentha oil also exhibited potent antioxidant activity in 2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulphuric acid (ABTS) bioassay. Keeping in mind the side effects of synthetic pesticides and the global interest in botanical pesticides for plant protection due to their biodegradable nature, M. arvensis oil may be used as a botanical fungitoxicant against fungal attack to stored food commodities. The antiaflatoxigenic and antioxidant nature of the oil suggest the possibility of its exploitation for enhancing the shelf life of stored food commodities. Copyright © 2007 Society of Chemical Industry     

Delivery systems for biological control agents to manage aflatoxin contamination of pre-harvest maize

While soil application of a competitive non-toxigenic Aspergillus flavus strains is successful in reducing aflatoxin contamination in certain crops, direct application to aerial reproductive structures could be more effective for maize. A sprayable, clay-based water-dispersible granule formulation was developed to deliver non-toxigenic A. flavus strain K49 directly to maize ears. The efficacy of the K49 water-dispersible granule in mitigating aflatoxin in maize (Zea mays L.) was evaluated. Field studies were conducted to compare K49 colonization and effectiveness in reducing aflatoxin contamination when applied either as a soil inoculant or as a directed spray in plots infested with toxigenic strain F3W4. Fifty percent of non-toxigenic A. flavus was recovered from non-treated controls and from plots soil inoculated with K49 on wheat. In spray treatments with formulated or unformulated K49 conidia, over 90% of A. flavus recovered was non-toxigenic. Soil-applied K49 reduced aflatoxin contamination by 65% and spray applications reduced contamination by 97%. These findings suggest direct spray application of non-toxigenic A. flavus strains may be better than soil inoculation at controlling maize aflatoxin contamination and that a water-dispersible granule is a viable delivery system for maintaining viability and efficacy of the biological control agent, K49.     

In vitro Antifungal Activity of Dehydrozingerone and its Fungitoxic Properties

Abstract: The efficacy of Dehydrozingerone (DZ; dehydroderivative of zingerone) as an antifungal agent and its mode of action against food spoilage fungal pathogens was studied and presented. DZ is a constituent of ginger (Zingiber officinale rhizomes) and structural half analogue of curcumin. Its efficacy against Aspergillus oryzae, Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus, Fusarium oxysporum and Penicillium chrysogenum was evaluated. Effect of DZ on the growth and sporulation of A. ochraceus was also studied. The fungal species were susceptible to DZ and the minimum inhibitory concentration and fungicidal concentration ranged from 755 to 911 μM and 880 to 1041 μM respectively. The mycelial and spore germination was significantly inhibited; reduction in the weight of the cell mass, carbohydrate, protein, DNA and RNA constituents in the cells isolated from cultures of A. ochraceus grown with DZ were observed. Scanning electron microscopy studies revealed morphological observations such as cell lysis, inhibition and morphological alterations in hyphae and sporulation in A. ochraceus on treatment with DZ. Practical application: Current investigations revealed that DZ is a potential antifungal agent and can find application as an additive or adjuvant in food and pharmaceutical industries after appropriate toxicological studies.     

Fermentation of table cream by Lactobacillus plantarum strains: effect on fungal growth,aflatoxin M1 and ochratoxin A

Aflatoxin M1 (AFM₁) and ochratoxin A (OTA) are two main mycotoxins in milk and dairy products. In the present work, the ability of four Lactobacillus strains (L. plantarum PTCC 1058, L. plantarum LP3, L. plantarum AF1 and L. plantarum LU5) to remove AFM1 and OTA in fermented cream was studied during 24 h fermentation. The antifungal activity of the mentioned lactobacilli against the defined fungi (Aspergillus flavus PTCC 5004, Aspergillus parasiticus PTCC 5018, Aspergillus nidulans PTCC 5014, Aspergillus ochraceus PTCC 5060) was also evaluated. The results showed that the cell counts of all strains were increased by 64–70% during fermentation. All Lactobacillus strains decreased the amount of AFM₁ significantly (P ≤ 0.05) in the range of 26–52%, which the highest AFM₁-reducing effect was related to L. plantarum LU5 (from 0.5 to 0.24 μg kg⁻¹). The mean OTA removal by Lactobacillus strains in fermented cream also ranged from 32 to 58%. Amongst Lactobacillus strains, the cell-free culture supernatants of L. plantarum LU5 showed the highest (inhibition zone of 26.7 ± 1.2 mm) and L. plantarum LP3 and L. plantarum PTCC 1058 the lowest antifungal activities. The fermented creams contained Lactobacillus strains exhibited the highest and lowest antifungal activities against A. ochraceus and A. parasiticus, respectively. L. plantarum LU5, with the inhibition zone of 27.6 ± 0.9 mm, was the most effective fungal inhibitor, while L. plantarum PTCC 1058 had the lowest antifungal activity.     

Aspergillus flavus population isolated from soil of Argentina's peanut‐growing region. Sclerotia production and toxigenic profile

The Aspergillus flavus population was evaluated in the period 1998–2001 in soil samples from the peanut‐growing region in Argentina. A total of 369 A flavus isolates were examined for sclerotia, aflatoxin and cyclopiazonic acid production. The L phenotype was isolated in a higher percentage than the S phenotype and represented 59% of the total isolates. Statistical analysis showed significant differences between L, S and non‐sclerotial strains with regard to aflatoxin and cyclopiazonic acid production (p < 0.05). The S strains produced higher mycotoxin levels than the L and non‐sclerotial strains. About 10% of the S strains had an unusual pattern of mycotoxin production because they simultaneously produce aflatoxins B and G and CPA. The S_BG strains isolated in the present study have all morphological and microscopic characteristics of A flavus. These strains are of concern in food safety, as there is a higher probability of aflatoxin contamination in peanuts. Copyright © 2005 Society of Chemical Industry     

Aflatoxin-producing potential of Aspergillus flavus and Aspergillus parasiticus isolated from samples of smoked-dried meat

Over a period of three years 420 samples of various smoke-dried meat products, collected from individual households in different region of Croatia were analysed for the presence of aflatoxigenic strains of the Aspergillus flavus group. Strains of A. flavus and A. parasiticus were present in 17,8% of the samples, and aflatoxin-producing ability was tested in 75 strains. In relation to sequential method of aflatoxin detection, 5 of 8 isolates were found in the first step (fluorescence in aflatoxin-producing ability medium - APA) and all of them in the second step (extraction method from syntheses on moist shredded wheat - SW). A. flavus strains produced mainly aflatoxin B₁, and had various levels of toxigenicity (1.4–3.12 mg/kg). Some strains of A. parasiticus produced all four aflatoxins B₁ B₂ G₁ G₂, while the other ones produced AF B₁ + G₁ only, with concentrations of aflatoxins from 0.1 to 450 mg/kg.