Effect of Capsicum carotenoids on growth and aflatoxins production by Aspergillus flavus isolated from paprika and chilli

The aim of this study was to determine the effect of a carotenoid mixture (Capsantal FS-30-NT), containing capsanthin and capsorubin, on growth and aflatoxins (AF) production of AF-producing Aspergillus flavus isolates.     

Fungi,mycotoxins and phytoalexin in peanut varieties,during plant growth in the field

The aim of the present study was to analyze the mycobiota, occurrence of mycotoxins (aflatoxins and cyclopiazonic acid), and production of phytoalexin (trans-resveratrol) in two peanut varieties (Runner IAC 886 and Caiapó) during plant growth in the field. Climatic factors (rainfall, relative humidity and temperature) and water activity were also evaluated. The results showed a predominance of Fusarium spp. in kernels and pods, followed by Penicillium spp. and Aspergillus flavus. Aflatoxins were detected in 20% and 10% of samples of the IAC 886 and Caiapó varieties, respectively. Analysis showed that 65% of kernel samples of the IAC 886 variety and 25% of the Caiapó variety were contaminated with cyclopiazonic acid. trans-Resveratrol was detected in 6.7% of kernel samples of the IAC 886 variety and in 20% of the Caiapó variety. However, trans-resveratrol was found in 73.3% of leaf samples in the two varieties studied.     

Aflatoxigenic fungi and aflatoxin in cocoa

This paper reports the occurrence of aflatoxigenic fungi and the presence of aflatoxins in 226 cocoa samples collected on Brazilian farms. The samples were taken at various stages of fermentation, drying and storage. A total of 819 potentially aflatoxigenic fungi were isolated using Dichloran 18% Glycerol agar after surface disinfection, and identified by standard techniques. The ability of the fungi to produce aflatoxins was determined using the agar plug technique and TLC. The presence of aflatoxins in cocoa samples was determined by HPLC using post-column derivatization with bromide after immunoaffinity column clean up. The aflatoxigenic fungi isolated were Aspergillus flavus, A. parasiticus and A. nomius. A considerable increase in numbers of these species was observed during drying and storage. In spite of the high prevalence of aflatoxigenic fungi, only low levels of aflatoxin were found in the cocoa samples, suggesting the existence of limiting factors to the accumulation of aflatoxins in the beans.     

Specific detection and quantification of Aspergillus flavus and Aspergillus parasiticus in wheat flour by SYBR® Green quantitative PCR

Aflatoxins are important mycotoxins that represent a serious risk for human and animal health. These mycotoxins are mainly produced by Aspergillus flavus and Aspergillus parasiticus, two closely related species with different array of aflatoxins. In this work, two specific quantitative PCR (qPCR) assays were developed to detect and quantify both species in wheat flour using primers based on the multicopy ITS2 rDNA target sequence. The species specificity of the assays was tested in a wide range of strains of these species and others colonizing the same commodities. The sensitivity of the assay was estimated in 2.5 pg/reaction in both species. Discrimination capacity for detection and relative quantification of A. flavus and A. parasiticus DNA were analyzed using samples with DNA mixtures containing also other fungal species at different ratios. Both qPCR assays could detect spore concentrations equal or higher than 10⁶ spores/g in flour samples without prior incubation. These assays are valuable tools to improve diagnosis at an early stage and in all critical control points of food chain integrated in HACCP strategies.     

Integrated management of insect vectors of Aspergillus flavus in stored maize, using synthetic antioxidants and natural phytochemicals

The purpose of this study was to investigate the insecticidal activity of two benzoic acids 2(3)-tert-butyl-4 hydroxyanisole (BHA) and 2,6-di(tert-butyl)-p-cresol (BHT); two phenolic acids 3-phenyl-2-propenoic acid (CA) and trans-4-hydroxy-3-methoxycinnamic acid (FA) and two essential oils of Eugenia caryophyllata (clove tree) and Thymus vulgaris (thyme) against Sitophilus zeamais, Tribolium confusum and Rhyzopertha dominica, vector carriers of aflatoxigenic fungi in stored maize. The susceptibility of insects, the frequency of isolation of Aspergillus section Flavi in insects and maize, and the analysis of aflatoxin B₁ in maize were determined. BHA, BHT, BHA/BHT mixture and the natural phytochemicals AF and AF/AC mixture showed the highest insecticidal activity against S. zeamais, T. confusum and R. dominica after 120 days of incubation. The insecticidal efficacy of the volatile fraction of essential oils of clove and thyme showed less inhibition. There was no contamination of Aspergillus section Flavi in dead and live insects collected from maize treated with BHA. No aflatoxin B₁ accumulation was detected in the control and treatments. The information obtained shows that these substances have the potential to control pest insect vectors of aflatoxigenic fungi in stored maize in microcosms during 120 days.     

Determination of aflatoxins in peanut butter and sesame samples using high-performance liquid chromatography method

In this study, total number of samples analysed were 20 packages of sesame and 20 cans of peanut butter, which were collected from Ankara local markets, Turkey. Extraction and determination of aflatoxins have been made by immunoaffinity column technique and high-performance liquid chromatography (HPLC) method. Mean levels (±SE) of aflatoxins B₁, B₂, G₁ were found to be 15.756±3.129 ng/g, 1.232±0.244 ng/g and 9.689±1.005 ng/g, respectively in peanut butter samples. Regarding the sesame samples, mean level of aflatoxin G₁ was found to be 0.754±0.213 ng/g. Our data revealed that while aflatoxin levels found in sesame samples were within the Turkish Food Codex (TFC) values, for peanut butter samples, they were higher than the TFC values.     

Aflatoxins’ fate during the nixtamalization of contaminated maize by two tortilla-making processes

The fate of aflatoxin B₁ and B₂ was studied during maize nixtamalization by two tortilla-making processes. High-quality maize seed (AS-900) was used, as well as a toxigenic strain of Aspergillus flavus. The grain moisture content was adjusted to 18%, and the incubation temperature was 27°C. One lot of grain served as the control and so was not inoculated with the fungus. At the end of the 13 d incubation period, this control lot was aflatoxin free (aflatoxin level 1). Two other lots were inoculated with the fungus and incubated for 12 and 14 d. They then had aflatoxin contamination of 29 and 93 ppb, respectively (aflatoxins levels 2 and 3). The quantification of aflatoxins was undertaken according to the AOAC Official Method 991.31 and their identification confirmed by HPLC. The maize grain was processed by the traditional (TNP) and the ecological (ENP) nixtamalization processes. Aflatoxins were quantified at all steps of the tortilla-making processes. The research was conducted under a completely randomized factorial design (2×3). In the case of tortillas processed with TNP, the total aflatoxin content was 2 and 9 ppb corresponding to aflatoxin levels 2 and 3 with a degradation rate of 92% and 90%, respectively. In tortillas obtained through the ENP, the aflatoxin content was 6 and 36 ppb for aflatoxin levels 2 and 3, with degradation rates of 78% and 61%, respectively. The TNP produced higher aflatoxin degradation rates than the ENP.     

Effect of three stored-grain fungi on the development of Typhaea stercorea

This study examined development times and ovipositional preference of hairy fungus beetles (Typhaea stercorea [L.] Col: Mycetophagidae), when reared on pure cultures of Aspergillus flavus Link, Eurotium rubrum König, Spieck and Bremer, and Penicillium purpurogenum Stoll., and the ability of hairy fungus beetles to develop in the presence of high levels of aflatoxin when fed A. flavus grown on coconut agar medium. Results indicate that hairy fungus beetles can complete their life cycle when fed these mold species grown on a defined medium in pure culture. Developmental times were shortest and females laid more eggs on pure cultures of A. flavus compared to E. rubrum, and P. purpurogenum. Lastly, we tested to see the effects of aflatoxin on hairy fungus beetle development. Hairy fungus beetles can complete their life cycle while feeding on a fungal culture producing high levels of aflatoxin. The results suggest that the mold species in the grain mass can influence insect developmental rates and thus population growth rates.     

Molecular biodiversity of mycotoxigenic fungi that threaten food safety

Fungal biodiversity is one of the most important contributors to the occurrence and severity of mycotoxin contamination of crop plants. Phenotypic and metabolic plasticity has enabled mycotoxigenic fungi to colonize a broad range of agriculturally important crops and to adapt to a range of environmental conditions. New mycotoxin-commodity combinations provide evidence for the ability of fungi to adapt to changing conditions and the emergence of genotypes that confer enhanced aggressiveness toward plants and/or altered mycotoxin production profiles. Perhaps the most important contributor to qualitative differences in mycotoxin production among fungi is variation in mycotoxin biosynthetic genes. Molecular genetic and biochemical analyses of toxigenic fungi have elucidated specific differences in biosynthetic genes that are responsible for intra- and inter-specific differences in mycotoxin production. For Aspergillus and Fusarium, the mycotoxigenic genera of greatest concern, variation in biosynthetic genes responsible for production of individual families of mycotoxins appears to be the result of evolutionary adaptation. Examples of such variation have been reported for: a) aflatoxin biosynthetic genes in Aspergillus flavus and Aspergillus parasiticus; b) trichothecene biosynthetic genes within and among Fusarium species; and c) fumonisin biosynthetic genes in Aspergillus and Fusarium species. Understanding the variation in these biosynthetic genes and the basis for variation in mycotoxin production is important for accurate assessment of the risks that fungi pose to food safety and for prevention of mycotoxin contamination of crops in the field and in storage.     

Distribution of metals and phenolic compounds as a criterion to evaluate variety of berries and related jams

Polyphenols, anthocyanins, phosphate, iron, zinc, manganese, calcium, potassium, magnesium and sodium were evaluated both in berries belonging to the genera Rubus and Ribes and in related jams by means of spectrophotometric techniques, to verify a possible differentiation on the basis of these parameters. The phenolic and anthocyanins higher contents were detected for black currant fruits and jams. Regarding the total phenolic content, in 11 cases it is possible to observe a higher content in jams with respect to the related row fruits. All samples contain a high amount of potassium, calcium and magnesium but small quantities of sodium. Phosphate is abundant especially in currants. As regard jams all results about metals are lower than those obtained for fruits, this is due to the dilution during the preparation of the jams. Multivariate statistical analysis shows that on the basis of obtained analytical results it is possible differentiate not only fruit but also the derived jams.     

Brazil nuts: Benefits and risks associated with contamination by fungi and mycotoxins

The monotypic type genus Bertholletia produces commercially nutritionally harvested edible seeds, Brazil nuts. It is an important product from the Amazon forest in the food production chain, with a 2008 annual world production of 78,000 tonnes, being Brazil responsible for approximately 40% of it. Although there are beneficial nutritional properties, the prevailing mycobiota of Brazil nuts include fungi that are producers of aflatoxins, such as Aspergillus flavus, A. parasiticus and A. nomius. Aflatoxins have deleterious effects in consumption considering the global distribution chain, affecting major exporting countries. The present review is focused on the importance of Brazil nuts for the Amazon rainforest, emphasizing on the social and environmental impact of its production, on the mycobiota contamination of seeds, and on the presence of mycotoxins and related food safety aspects.     

Antioxidant potential of ethanolic extract of Polygonum cuspidatum and application in peanut oil

Polygonum cuspidatum was extracted with 95% ethanol to obtain a crude antioxidant extract. P. cuspidatum extract (PCE) had a very high content of total phenol, which was 104.83 ± 8.58 mg/g dry weight, expressed as pyrocatechol equivalent. PCE exhibited excellent antioxidant activity, as measured using α,α-diphenyl-β-picryhydrazyl (DPPH) and total antioxidant assays. It also showed a high lipid antioxidant activity and hydroxyl radicals scavenging activity. A positive correlation was found between the reducing power and the antioxidant activity of PCE, which was found to be comparable to resveratrol and butylated hydroxytoluene (BHT). Then the suitability of PCE as an antioxidant was determined in peanut oil, and the decrease of oxidation was monitored using thiobarbituric acid-reactive substances (TBARS) assay. PCE treatment significantly (P <  0.05) reduced lipid oxidation in peanut oil compared to resveratrol and BHT.     

A survey of pre-harvest ear rot diseases of maize and associated mycotoxins in south and central Zambia

Maize ear rots reduce grain yield and quality with implication on food security and health. Some of the pathogenic fungi produce mycotoxins in maize grain posing a health risk to humans and livestock. Unfortunately, the levels of ear rot and mycotoxin infection in grain produced by subsistence farmers in sub-Saharan countries are not known. A survey was thus conducted to determine the prevalence of the ear rot problem and levels of mycotoxins in maize grain. A total of 114 farmsteads were randomly sampled from 11 districts in Lusaka and southern provinces in Zambia during 2006. Ten randomly picked cobs were examined per farmstead and the ear rot disease incidence and severity were estimated on site. This was followed by the standard seed health testing procedures for fungal isolation in the laboratory. Results indicated that the dominant ear rots were caused by Fusarium and Stenocarpella. Incidence of Fusarium verticillioides ranged from 2 to 21%, whereas that of Stenocarpella maydis reached 37% on ear rot diseased maize grain. In addition, 2-7% F. verticillioides, and 3-18% Aspergillusflavus, respectively, were recovered from seemingly healthy maize grain. The mean rank of fungal species, from highest to lowest, was F. verticillioides, S. maydis, A.flavus, Fusarium graminearum, Aspergillus niger, Penicillium spp., Botrydiplodia spp., and Cladosporium spp. The direct competitive ELISA-test indicated higher levels of fumonisins than aflatoxins in pre-harvest maize grain samples. The concentration of fumonisins from six districts, and aflatoxin from two districts, was 10-fold higher than 2 ppm and far higher than 2 ppb maximum daily intake recommended by the FAO/WHO. The study therefore suggested that subsistence farmers and consumers in this part of Zambia, and maybe also in similar environments in sub-Saharan Africa, might be exposed to dangerous levels of mycotoxins due to the high levels of ear rot infections in maize grain.     

Antioxidant activity of ethanolic extract of Cortex fraxini and use in peanut oil

Cortex fraxini was extracted with 95% ethanol to obtain a crude antioxidant extract. The antioxidant activity was evaluated using the linoleic acid peroxidation method and the free radical scavenging assays, namely 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals. Cortex fraxini extract (CFE) showed high inhibition of peroxidation of linoleic acid when compared with butylated hydroxytoluene (BHT). CFE also exhibited excellent scavenging activity on DPPH and hydroxyl radicals. Total antioxidant activity was measured by the reduction of Mo(VI) to Mo(V) by the extract, and subsequent formation of a green phosphate/Mo(V) complex at acid pH. CFE had significant total antioxidant activity and the effects were increased with increasing reaction time. The total phenolic content of the sample, analyzed by using Folin–Ciocalteu’s reagent, was 91.33 mg/g dry weight expressed as pyrocatechol equivalents. Then the suitability of CFE as an antioxidant was determined in peanut oil, and the decrease of lipid oxidation was monitored using thiobarbituric acid-reactive substances (TBARS) assay. CFE treatment significantly (P < 0.05) reduced lipid oxidation in peanut oil compared to the control. No significant differences (P = 0.05) in lipid oxidation were detected between CFE antioxidant and BHT antioxidant samples.     

Development of a class-specific monoclonal antibody-based ELISA for aflatoxins in peanut

Three class-specific monoclonal antibodies against aflatoxins were screened by a designed strategy in which aflatoxin G₂ was used as competitor in the screening ELISA system. With a high cross-reactivity (65%) to aflatoxin G₂, antibody 10C9 had the most similar sensitivity for five aflatoxins (AFB₁, AFB₂, AFG₁, AFG₂ and AFM₁), whose I₅₀ values were in a range of 2.1–3.2 ng ml⁻¹. So, antibody 10C9 was selected to develop an ELISA for determination of aflatoxin B₁, B₂, G₁, G₂ and total of them in peanut samples. And spiked recoveries were from 87.5% to 102.0%. The results indicate that the ELISA developed can accurately determine total aflatoxins in samples of peanuts after the simple and rapid extraction procedure.     

Antifungal potential of some natural products against Aspergillus flavus in soybean seeds during storage

The inhibitory effect of cow-dung fumes, captan, leaf powder of Withania somnifera, Hyptis suaveolens, Eucalyptus citriodora, peel powder of Citrus sinensis, Citrus medica and Punica granatum, neem cake and pongamia cake on the growth of Aspergillus flavus in soybean seeds during storage was investigated. Soybean seed was treated with different natural products and the fungicide captan and was stored at ambient conditions for 6 months. Seed samples were withdrawn at monthly intervals and the incidence of seed-borne A. flavus and percentage germination of the seed was determined. Captan, neem cake, pongamia cake and peel powder of C. sinensis reduced the incidence of A. flavus. Leaf powder of W. somnifera, H. suaveolens, E. citriodora and peel powder of P. granatum also checked the frequency of A. flavus. All treatments maintained a high germination percentage of the soybean seeds over a storage period of 6 months. These natural products may be alternatives to chemical fungicides and provide an easy method to protect soybean and other agricultural commodities from A. flavus in storage.     

Degradation of aflatoxins by extrusion cooking: Effects on nutritional quality of extrudates

Extrusion of artificially contaminated food is reported to degrade aflatoxins to varying degrees depending on the extrusion conditions. This work sought to determine the (1) efficacy of extrusion cooking in destroying naturally contaminated peanuts and (2) nutritional quality of decontaminated peanut meal. Naturally contaminated peanut meal was extruded by varying the moisture (20, 28, 35 g/100 g), pH (7.5, 9.5) and extruder die diameter (2.5, 3, 3.5, 4.0 mm). Aflatoxins levels in the extrudates were determined using HPLC procedures, and the nutritional quality was assessed using in-vitro methods. The highest aflatoxin reduction in naturally contaminated peanut meal was 59% at feed moisture content of 35 g/100 g. Higher (91%) reduction was achieved in the artificially contaminated peanut meal at moisture of 20 g/100 g. In-vitro protein digestibility and Fluorodinitrobenzene (FDNB)-available lysine of the extrudates were not significantly different from non-extruded peanut meal. Extrusion conditions for aflatoxin reduction did not adversely affect protein nutritional quality.     

Inhibitory effect of the essential oil of Curcuma longa L. and curcumin on aflatoxin production by Aspergillus flavus Link

Aflatoxins are highly toxic, mutagenic, teratogenic and carcinogenic mycotoxins. Consumption of aflatoxin-contaminated food and commodities poses serious hazards to the health of humans and animals. Turmeric, Curcuma longa L., is a native plant of Southeast Asia and has antimicrobial, antioxidant and antifungal properties. This paper reports the antiaflatoxigenic activities of the essential oil of C. longa and curcumin. The medium tests were prepared with the oil of C. longa, and the curcumin standard at concentrations varied from 0.01% to 5.0%. All doses of the essential oil of the plant and the curcumin standard interfered with mycotoxin production. Both the essential oil and curcumin significantly inhibited the production of aflatoxins; the 0.5% level had a greater than 96% inhibitory effect. The levels of aflatoxin B₁ (AFB₁) production were 1.0 and 42.7 μg/mL, respectively, for the samples treated with the essential oil of C. longa L. and curcumin at a concentration of 0.5%.