Influence of cold plasma on fungal growth and aflatoxins production on groundnuts

In this study, influence of cold plasma on the Aspergillus parasiticus and Aspergillus flavus growth and aflatoxins productions have been investigated as an alternative to chemical free and thermal treatments. Artificially inoculated fungal species onto the groundnuts were treated with air plasma at 40 W and 60 W power levels at various time intervals. After the plasma treatment, inactivation of A. parasiticus and A. flavus was examined and the concentration of aflatoxins produced was analyzed using high performance liquid chromatography. There is 97.9% and 99.3% reduction in the growth of A. parasiticus and A. flavus respectively, when treated at 60 W powers. Electron microscopy was also used to study the effect of cold plasma on the cellular membranes of the spores. Results showed complete disintegration of fungal spore membrane due to electroporation and etching caused by the reactive species of plasma. In 40 W 15 min and 60 W 12 min plasma treated samples more than 70% and 90% reduction in aflatoxin B1 content was observed. These results suggest that cold plasma may be considered as alternative methods for disinfestation of foods due to its strong potential for microbial inactivation.     

Inactivation of Aspergillus flavus spores by curcumin-mediated photosensitization

Minimizing fungal infection is essential to the control of mycotoxin contamination of foods and feeds but many potential control methods are not without their own safety concerns for the consumers. Photodynamic inactivation is a novel light-based approach which offers a promising alternative to conventional methods for the control of mycotoxigenic fungi. This study describes the use of curcumin to inactivate spores of Aspergillus flavus, one of the major aflatoxin producing fungi in foods and feeds. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa). In this study the plant has shown to be an effective photosensitiser when combined with visible light (420 nm). The experiment was conducted in in vitro and in vivo where A. flavus spores were treated with different photosensitiser concentration and light dose both in buffer solution and on maize kernels. Comparison of fungal load from treated and untreated samples was determined, and reductions of fungal spore counts of up to 3 log CFU ml⁻¹ in suspension and 2 log CFU g⁻¹ in maize kernels were obtained using optimal dye concentrations and light dose combinations. The results in this study indicate that curcumin-mediated photosensitization is a potentially effective method to decontaminate A. flavus spores in foods and feeds.     

Upland rice vinegar vapor inhibits spore germination,hyphal growth and aflatoxin formation in Aspergillus flavus on maize grains

The efficacy of vapor-phase (VP) upland rice vinegar (URV) was investigated as a bio-fumigant for maize, to reduce consumer health risks associated with spore and toxin formation by Aspergillus flavus. Complete reduction of mycelial growth occurred with in vitro VP exposure to URV (containing 0.0017 mmol/L acetic acid) or with VP exposure to pure acetic acid (PAA) (containing 0.0023 mmol/L acetic acid). No significant differences were observed between the two materials after 90 min exposures. Using gas chromatography-mass spectrometry (GC-MS), URV vapor was shown to contain volatiles having antifungal activities. These are identified as isoamylalcohol, 1-butanol, 3-methyl-, acetate and β-phenylethyl acetate. It is suggested these volatiles increase the antifungal effectiveness of URV. Exposure to VP-URV (containing 0.0043 mmol/L AA) for 5 h completely eliminated viable spores of A. flavus on maize seeds (23% moisture content) previously inoculated with 4.43 ± 0.28 log spores/g). At the same time, aflatoxin production decreased, as VP-URV exposure increased. Hence, VP-URV is shown to be an effective control agent for A. flavus mycelial growth and aflatoxin formation on maize, so effectively reducing the potential for consumer health risks due to this widespread fungus.     

Effect of Hibiscus sabdariffa extract and Nigella sativa oil on the growth and aflatoxin B1 production of Aspergillus flavus and Aspergillus parasiticus strains

This study was undertaken to evaluate the inhibitory effect of Hibiscus sabdariffa calyx extract at concentrations of 5, 7.5, 10 and 12.5 g/100 ml and Nigella sativa oil at concentrations of 1, 2 and 3 ml/100 ml on the growth and aflatoxin B₁ production by Aspergillus parasiticus (CBS 921.7) and Aspergillus flavus (SQU 21) strains. The inhibition of aflatoxin B₁ production by the different concentrations of H. sabdariffa calyx ranged between 91.5-97.9% and 87.1-93.3% for A. flavus and A. parasiticus strains, respectively, whereas the inhibition by different concentrations of N. sativa oil ranged between 47.9 and 58.3% for A. flavus and 32-48% for A. parasiticus strains. The different concentrations of H. sabdariffa calyx and N. sativa oil had no significant effect on the growth of either Aspergillus species. Neither H. sabdariffa calyx nor N. sativa oil detoxified pure aqueous aflatoxin. Our results suggest that H. sabdariffa calyx and N. sativa oil extracted from seeds had metabolic effects on aflatoxin biosynthesis pathway of both Aspergillus species and can be used as an effective biocontrol and non-toxic biopreservatives in food industry against aflatoxin contamination.     

Biological activities of Boswellia sacra extracts on the growth and aflatoxins secretion of two aflatoxigenic species of Aspergillus species

Aflatoxins are the most serious carcinogenic, hepatotoxic, teratogenic and mutagenic secondary metabolites which adversely affect human and animal health. This study was designed to evaluate the in vitro inhibitory effect of different concentrations of Boswellia sacra resin (2.5, 5, 7.5 and 10 g/100 ml), leaf extract (5, 7.5, 10, 12.5 and 15 ml/100 ml), and essential oil (1, 2, 3, and 4 ml/100 ml) on the growth and aflatoxins production by two species of Aspergilli, namely Aspergillus flavus (SQU21) and Aspergillus parasiticus (CBS921.7). Resin of B. sacra caused 57.9–92.1% inhibition of aflatoxin secretion by A. flavus and 43.6–95.7% for A. parasiticus. However, the mycelial dry weights were significantly increased by 20.9–52.7% for A. flavus, and 8.9–68.5% for A. parasiticus. The leaf extract of B. sacra apparently enhanced aflatoxins production by 20–50%, and mycelial dry weight by 25.5–29.1% for A. flavus and A. parasiticus. The essential oil of B. sacra at different concentrations similarly inhibited the fungal growth and aflatoxins production by 45.8–83.7% for A. flavus and 41.3–83.5% for A. parasiticus which indicates the antifungal activity of this oil. None of the B. sacra extracts detoxified pure aqueous aflatoxin B₁. We have concluded that B. sacra resin and essential oil possess biological activity against biochemical synthesis and metabolic pathway of aflatoxin production of the two Aspergillus species. Therefore, the resin and essential oil of B. sacra can be recommended as safe plant based bioreservatives to enhance shelf life of food and feed products with reference to adverse effect of physical and synthetic chemical preservatives and their antimicrobial and aflatoxins inhibition activity.     

Mycological quality and mycotoxin contamination of Sri Lankan peppers (Piper nigrum L.) and subsequent exposure assessment

The aim of the study was to characterize the toxigenic moulds and to screen different mycotoxins in peppers (Piper nigrum L.) of Sri Lankan origin. Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger and Penicillium spp. were found to be the most dominant fungi. Characterization of the moulds was carried out in A. flavus and parasiticus agar (AFPA) and malt extract agar (MEA) in 77 black pepper (BP) and 11 white pepper (WP) samples. In total, 73% of the BP and 64% of the WP samples were contaminated with A. flavus and/or A. parasiticus (AfAp). A BP sample with water activity (a_w) 0.70 recorded the highest count of AfAp (4.3*10⁴ CFU/g). Moreover, 75% of the BP samples exceeded the safe a_w limit (0.65) set by the European Spice Association (ESA). The frequency of occurrence of A. niger in BP was 62% with counts up to 1.3*10³ CFU/g. Penicillium spp. were found in 61% and 55% of the BP and WP samples, respectively. In BP 94% of the samples had a Penicillium contamination below 10³ CFU/g. Other Aspergillus spp, found in peppers included, Aspergillus terrus, Aspergillus tamarii, Aspergillus candidus, Aspergillus penicilloides, Aspergillus sydowii and Aspergillus fumigatus. Mould counts in BP (10²–10⁴ CFU/g) were significantly higher than that of WP (<10² CFU/g). Apart from the occurrence of “classical mycotoxins” of spices, aflatoxins (<LOQ-18 μg/kg) and ochratoxin A (<LOQ-79 μg/kg), other toxins including fumonisin B1 (<LOQ-135 μg/kg), sterigmatocystin (<LOQ-49 μg/kg) and citrinin (<LOQ-112 μg/kg) were detected in peppers. In total, 63% of the BP samples were contaminated with at least one mycotoxin. Mycotoxin contamination in WP was significantly less compared to BP. The exposure to aflatoxins and ochratoxin A by consuming pepper remains harmless considering the existing pepper dietary intake data of the Sri Lankan population.     

Aflatoxigenic fungi and aflatoxins occurrence in sultanas and dried figs commercialized in Brazil

The presence of aflatoxins, Aspergillus flavus and Aspergillus parasiticus in dried fruits was investigated. A total of 62 dried fruit samples were analyzed (24 black sultanas, 19 white sultanas and 19 dried figs). A total of 10 A. flavus isolates were found, nine in one white sultana sample (corresponding to 18% infection) and one isolate in dried figs (2%), and all of them were aflatoxin B₁ and B₂ producers. A. parasiticus was not found. Aflatoxins were detected in 3 of 19 (16%) white sultana samples analyzed and, the limits were not higher than 2.0 μg/kg. In dried figs 11 of 19 (58%) samples were contaminated with aflatoxins and, with exception of one sample that was contaminated with 1500 μg/kg of B₁ aflatoxin, the others had less than 2.0 μg/kg. Neither aflatoxigenic or aflatoxins contaminated black sultanas.     

The potential of some spice essential oils in the control of A. parasiticus CFR 223 and aflatoxin production

Essential oils of sweet basil (Ocimum basilicum), cassia (Cinnamomum cassia), coriander (Coriandrum sativum) and bay leaf (Laurus nobilis) at 1–5% (v/v) concentration in palm kernel broth inoculated with spore suspension (10⁶/ml) of Aspergillus parasiticus CFR 223 were evaluated for their potential in the control of aflatoxigenic fungus A. parasiticus CFR 223 and aflatoxin production. Healthy sorghum grains (120/treatment) immersed in the oils and distributed in three petri dishes with wet cotton wool were also inoculated with spore suspension (10⁶/ml) of A. parasiticus CFR 223 and assayed for grain protection. Sweet basil oil at optimal protective dosage of 5% (v/v) was fungistatic on A. parasiticus CFR 223 and aflatoxins produced in vitro and on fungal development on sorghum grains (P ⩽ 0.05) with a residual effect that lasted for 32 days. In contrast, oils of cassia and bay leaf stimulated the mycelia growth of the fungus in vitro but reduced the aflatoxin concentration (B₁ + G₁) of the fungus by 97.92% and 55.21% respectively, while coriander oil did not have any effect on both the mycelia growth and aflatoxin content of the fungus. The combination of cassia and sweet basil oils at half their optimal protective dosages (2.5% v/v) completely inhibited the growth of the fungus. The feasibility of implementing the results of this study to control aflatoxins was examined by the addition of whole and ground dry basil leaves at 5% and 10% (w/w), respectively, to 10 g sorghum, groundnut, maize and melon seed after 35 days storage period. It was found that the addition of whole and ground basil leaves markedly reduced aflatoxin contamination; however, 10% (w/w) of whole leaves was more effective as the reduction in aflatoxin was between 89.05% and 91%.The findings showed that aflatoxins can be controlled by co-storing whole sweet basil leaves with aflatoxin infected foods. The economic value of the study lies in the simplified technique for control of aflatoxin contamination in agricultural products and the benefits derivable from the use of local resources.     

Detection of potentially mycotoxigenic Aspergillus species in Capsicum powder by a highly sensitive PCR-based detection method

The objective of this study was to gain information about the toxigenic Aspergillus species present in a wide survey of retail samples of paprika and chilli collected in Spain. Detection of these mycotoxigenic species was performed with an optimized protocol for paprika and chilli which includes a set of species-specific PCR assays. Occurrence of toxigenic Aspergillus species was higher in paprika than in chilli samples (83.9% and 64.5%, respectively). Paprika showed also the highest percentage of co-occurrence of two or more different species (43.6%) in comparison with chilli (35.5%). The most common aspergilli were Aspergillus niger aggregate (67.7%), followed by Aspergillus flavus (49.5%). Aspergillus carbonarius, Aspergillus parasiticus and Aspergillus steynii were detected at lower frequency (1.1%). The high co-occurrence of Aspergillus species able to produce ochratoxin A and aflatoxins, particularly in paprika, suggested the need of a more efficient control during processing and storage to reduce fungal contamination, and additional legislation to consider the simultaneous presence of both toxins in these matrices.     

Iturin produced by Bacillus pumilus HY1 from Korean soybean sauce (kanjang) inhibits growth of aflatoxin producing fungi

A new strain of Bacillus pumilus, designated HY1, was isolated from Korean soybean sauce (kanjang). This classification was based on morphological, physiological, and chemotaxonomic features of the organism that identified it as a Gram-positive bacillus, and confirmed by 16S rDNA based phylogenetic analysis. Strain HY1 showed strong antifungal activity against the aflatoxin-producing fungi Aspergillus flavus and Aspergillus parasiticus, two common contaminants of fermented soybean foods. MALDI-TOF mass analysis revealed that the antifungal compound was similar to the known lipopeptide iturin. Iturin purified from strain HY1 had three isoforms with protonated masses of m/z 1,043.4, 1,057.4, and 1,071.4, and different structures in combination with Na⁺ ion using MALDI-TOF MS. Purified iturin from HY1 also exhibited antifungal activity against A. flavus and A. parasiticus.     

Aflatoxin B1 production by Aspergillus parasiticus and strains of Aspergillus section Nigri in currants of Greek origin

Aflatoxin B₁ (AFB₁) mostly produced by Aspergillus flavus and Aspergillus parasiticus, is an extremely toxic and carcinogenic metabolite. Currants are used in the Mediterranean diet as a food with antioxidant properties. Four strains of Aspergillus section Nigri have been isolated from currants originated from Crete and Corinth. In this study AFB₁ production by A. parasiticus and the four strains of Aspergillus section Nigri in Cretan and Corinthian currants (Vitis vinifera L.) is investigated. AFB₁ determination was performed by HPLC–FID. Results revealed that the four strains Aspergillus section Nigri, as well as the aflatoxigenic strain A. parasiticus produced AFB₁ (0.0052–1.31 μg AFB₁ 15 g⁻¹, corresponding to 0.0003–0.087 μg AFB₁ g⁻¹) in both type of currants (Cretan and Corinthian) on the 12th day of observation. Moreover, AFB₁ production, by A. parasiticus in the synthetic Yeast Extract Sucrose (YES) medium was also studied. The ability of AFB₁ production has been affected by the special characteristics of each isolate and the currants substrate.     

Inhibition of non-toxigenic Aspergillus niger FS10 isolated from Chinese fermented soybean on growth and aflatoxin B1 production by Aspergillus flavus

A non-toxigenic strain FS10 was isolated from Chinese fermented soybean to control AFB₁ contamination and conformed as Aspergillus niger by 18S rDNA. To elucidate the biocontrol mechanism, the ability of culture filtrate of strain FS10 against growth and AFB₁ production by toxigenic Aspergillus flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by optical microscope and atomic force microscope (AFM). Results demonstrated that the culture filtrate of FS10 significantly suppressed A. flavus growth, sporulation and AFB₁ biosynthesis. After 9 days, the inhibition of mycelia growth, sporulation and AFB₁ production reached to 37.7%, 100% and 94.5%, respectively. In addition, optical microscopy and AFM showed that the culture filtrate serious damaged spore morphology, accompanying with spore analysis and cell wall collapse, resulted in inhibition of spore germination. The degradation activity of FS10 culture filtrate on AFB₁ was also estimated. When AFB₁ was incubated with the culture filtrate, 85.8% of AFB₁ could be degraded after 5 days. It is concluded that the culture filtrate of strain FS10 has pleiotropic effects on control AFB₁ contamination. As a safe, effective and economic biological agent, the filtrate could be applied in fermented food to prevent toxigenic Aspergillus spp. and AFB₁ contamination.     

Antifungal activity of Michelia alba oil in the vapor phase and the synergistic effect of major essential oil components against Aspergillus flavus on brown rice

The objectives of this study were to investigate the effect of essential oil (Michelia alba) vapor on the spore germination and mycelium growth of Aspergillus flavus on brown rice and to perceive the shelf life of the brown rice could be extended to a longer storage time. Different volumes (150, 300, 450 μl) of M. alba and a 300 μl linalool/caryophyllene combination at ratios of 10:1, 1:1, and 1:10 were first absorbed into plant absorbent material (Φ∼20 mm) before being put into a closed glass box (1L) containing A. flavus spore and the mycelium (Φ∼5 mm) in a Malt Extract Agar (uncovered plate). Mold testing was also carried out on brown rice with A. flavus spore suspension before being incubated at 25° C and 100% RH for 16 weeks. Quality tests e.g. texture, a sensorial evaluation (hedonic scale) of brown rice were also conducted. Results indicated that the vapor phase of M. alba at ≥ 300 μl L⁻¹ air could inhibit both spore germination and A. flavus mycelium. Antifungal activity of M. alba in air was strongly correlated with the linalool/caryophyllene combination at the ratio of 10:1 in 300 μl L⁻¹ air. In addition, M. alba vapor at 300 μl L⁻¹ air was found to extend the shelf-life of the brown rice by four times (16 weeks) in comparison with the control treated without essential oil (4 weeks). After being cooked, the hardness of brown rice with volatile essential oil was found to be reduced by one third (compared to the control brown rice). The hedonic value (overall liking) of cooked brown rice packed with M. alba vapor at 300 μl for 1 week and then stored for 16 weeks was a 7, rated as “like moderately”. Therefore, this study has demonstrated the good potential of M. alba vapor to control mold growth on the surface of brown rice.     

Comparative study of the simultaneous action of three essential oils on Aspergillus flavus and Sitophilus zeamais Motsch

Maize is among the most important produced and consumed crops in Cameroon. However, the availability of this cereal is limited by post-harvest losses, especially in the course of storage. Therefore, there is an urgent need to overcome this phenomenon through the use of efficient, cheap methods. To this effect, the simultaneous action of three essential oils, obtained by hydrodistillation from leaves of Ocimum gratissimum and Lippia rugosa and fruits of Xylopia aethiopica, on Aspergillus flavus and Sitophilus zeamais was investigated using a 2⁴ factorial design. The three essential oils and the storage time were considered as factors. The results revealed that low volume (60 μl/200 g grain) for O. gratissimum and high volume for L. rugosa (310 μl/200 g grain) and X. aethiopica (250 μl/200 g grain) showed the most important efficiencies against A. flavus and S. zeamais in a 2 weeks storage. Hence, the rate of mortality for S. zeamais was 92% and 89%, respectively, in samples of maize infested by S. zeamais and samples of maize infested by S. zeamais and A. flavus. Ninety five percent of A. flavus conidia were inhibited in samples of maize infested by A. flavus and samples of maize infested by S. zeamais and A. flavus.     

Aflatoxin-producing Aspergillus spp. and aflatoxin levels in stored cassava chips as affected by processing practices

Cassava chips (cassava balls, and cassava pellets) are derived cassava products traditionally produced by farmers in sub-Saharan Africa following fermentation, and drying of fresh roots of cassava, and are widely consumed in Cameroon. Once produced, this food commodity can be stored for more than two months and contaminated by a wide array of harmful microbes. In order to assess persistence of toxigenic fungi in cassava chips, aflatoxin-producing fungi (Aspergillus flavus, Aspergillus nomius, and Aspergillus parasiticus) and aflatoxins were contrasted at regular intervals in home-stored cassava chips collected in two locations of southern Cameroon throughout a two-month monitoring period. Three hundred and forty-six isolates of aflatoxin-producing fungi were found to be associated with all samples. A. flavus contaminated more samples in both types of chips (267 isolates in 53 samples), followed by A. nomius (58 isolates in 15 samples), whereas A. parasiticus was rarest. A direct competitive Enzyme-linked immunosorbent assay (ELISA)-based method was implemented to quantify the content in aflatoxins. Eighteen of the samples contained some aflatoxins at detectable levels whereas 54 did not. The levels of aflatoxin ranged between 5.2 and 14.5 ppb. The distribution of aflatoxin in positive samples depended on 8 parameters including pH, moisture content, storage duration, types of chips, level of contamination by aflatoxin-producing fungi, processing practices and storage facilities. From analysis of variance results, only pH (p < 0.01), duration of storage (p < 0.01), population of aflatoxin-producing species (0.0001) and the chip type (p < 0.05) were significantly related to aflatoxin in positive samples. A stepwise regression analysis (forward selection procedure) indicated that aflatoxin levels were significantly (p < 0.01) correlated with processing practices, storage facilities, and storage duration of the chips.     

Inactivation of aflatoxigenic fungi and the reduction of aflatoxin B1 in vitro and in situ using gamma irradiation

Detailed investigation on the effect of gamma (γ) irradiation on germination, sporulation, and growth of aflatoxigenic moulds (Aspergillus parasiticus 2999, Aspergillus flavus 305, and Aspergillus niger 388), as well as on the reduction of aflatoxin B₁ (AFB₁) level in artificially and naturally contaminated maize/feed samples was performed. The results of in vitro and in situ experiments with aflatoxigenic moulds demonstrated that 5 kGy-γ irradiation manages to prevent sporulation, germination and growth of the tested moulds both when in form of a pure and when in form of a mixed culture. In the feed samples artificially contaminated with AFB₁ (50 μg kg⁻¹) 5 kGy-γ irradiation reduced AFB₁ level by around 60%, while 10 kGy-dose reduce it for around 85%. Similarly, in feed samples spiked with AFB₁ in the concentrations of 100 μg kg⁻¹ 5 kGy-dose reduced the AFB₁ level by approximately 70%, while the dose of 10 kGy reduced it by approximately 90%. The experiments on naturally contaminated maize samples (n = 30) confirmed these observations; following a 5 kGy-irradiation, the overall mean AFB₁ reduction equalled to 69.8%, while the irradiation with a 10 kGy-dose achieved the overall mean toxin reduction of 94.5%. The obtained results indicate that γ irradiation can be used to prevent the growth of aflatoxigenic moulds and to reduce the AFB₁ levels in various goods intended for animal and human consumption, thus minimizing the animal and human exposure to this carcinogenic mycotoxin.     

Microbial safety and quality attributes of milk following treatment with atmospheric pressure encapsulated dielectric barrier discharge plasma

This study evaluated the microbial and physicochemical characteristics of milk that was treated with encapsulated dielectric barrier discharge (DBD) plasma. Encapsulated DBD plasma was generated in a plastic container (250 W, 15 kHz, ambient air) and DBD plasma treatment was applied to milk samples for periods of 5 and 10 min. The total aerobic bacterial count in the untreated control sample was 0.98 log CFU/mL. Following plasma treatment, no viable cells were detected in the milk samples. When milk samples were inoculated with Escherichia coli, Listeria monocytogenes, and Salmonella Typhimurium, plasma treatment for 10 min resulted in a reduction in bacterial counts by approximately 2.40 log CFU/mL. The pH of the sample milk was found to decrease after the 10-min plasma treatment. Hunter color L* and b* values of milk increased, and the a* value decreased as a result of the plasma treatment. The production of 2-thiobarbituric acid reactive substances increased slightly, but not significantly, following plasma treatment. The results of this study indicate that encapsulated DBD plasma treatment for less than 10 min improved the microbial quality of milk with slight changes in physicochemical quality of milk.     

Decontamination of whole black pepper using different cold atmospheric pressure plasma applications

Whole black pepper is a dry product, which is often naturally contaminated with bacterial endospores and sometimes also with human pathogens like Salmonella. Dry pepper itself is a shelf-stable product, but if it is incorporated into high moisture minimally processed food, the microorganisms can reduce the shelf-life of the final product and/or can cause foodborne diseases. In this study the antimicrobial effect of two different atmospheric pressure plasma applications for the decontamination of whole black pepper was investigated. Naturally contaminated peppercorns and with Bacillus subtilis spores, Bacillus atrophaeus spores and Salmonella enterica inoculated ones were treated using a plasma jet or a microwave-driven remote plasma. Surface color and the content of essential oils and piperine was measured. S. enterica, B. subtilis spores and B. atrophaeus spores were reduced by 4.1, 2.4 and 2.8 log, respectively, after 30 min remote plasma treatment. Direct plasma jet treatment did not result in equivalent inactivation levels. However, both plasma applications did not considerable affect the quality parameters.     

Mycoflora and absence of aflatoxin contamination of commercialized cassava chips in Benin, West Africa

Studies conducted in Benin, in which the main staple foods are maize, cassava, groundnuts and yams, showed high levels of aflatoxin residues in blood of the exposed population. The natural contamination with fungi and aflatoxins in cassava chips sold at markets in Benin, West Africa was investigated. A total of sixty samples were sampled from open markets in 11 districts of 3 agroecological zones and analyzed for the presence of mycoflora and aflatoxin B₁, B₂, G₁ and G₂. Fourteen genera of fungi were associated with marketed dried cassava chips. Within these, twenty- two isolates were identified to species level, whereas four were identified only to genus. The dominating fungal species isolated were Rhizopus oryzae, Nigrospora oryzae, Chrysonilia sitophila, Cladosporium resinae, Cladosporium herbarum, Apergillus niger and Aspergillus flavus. Fifty-four out of sixty samples were contaminated with A. flavus. The rate of occurrence in CFU/g of A. flavus fungi was lower than for all other fungal species together. Aflatoxin was not detected in any of the samples analyzed using HPLC with post-column photochemical derivatization and fluorescence detection. The limit of detection (LOD) was 0.1 μg/kg. Results from this study suggest cassava chips are unlikely to be a source of aflatoxin in Benin, and that other staples such as maize and groundnuts are more important in aflatoxin exposure. Therefore it can be speculated that staples like maize and groundnut are more important in aflatoxin exposure.     

Effect of low-dose microwave radiation on Aspergillus parasiticus

The effect of low-dose microwave radiation (LDMR; 2.45 GHz, 1.5 W/g) on biochemical characteristics and mortality of Aspergillus parasiticus was investigated and compared to the effects of conventional heating treatment (water bath), in order to provide a theoretical basis for microwave control of mildew in rice and other food products. The effects of LT50 (52 ± 2 °C) and LT100 (72 ± 2 °C) with microwave treatment on A. parasiticus were both lower than those (62 ± 2 °C and 92 ± 2 °C, respectively) with conductive heating. LDMR and conventional heating treatment both caused increased cell membrane permeability, and thus an increase in electrolyte, Ca²⁺, protein and DNA leakage, and the surface of mycelia appeared rough and swollen. LDMR was more effective in disrupting the cell membrane and causing DNA damage than conductional heating. The severity of DNA injury increased with the rise in temperature. The mechanism causing death of the mold evidently differed between LDMR and conventional heating treatment. LDMR led to the death of A. parasiticus mainly through the increased Ca²⁺ permeability and DNA degradation, and conventional heating treatment induced death mainly by augmenting electrolyte permeability and DNA concentration.