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.     

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.     

Inhibitory of multiple antifungal components produced by Lactobacillus plantarum K35 on growth,aflatoxin production and ultrastructure alterations of Aspergillus flavus and Aspergillus parasiticus

The antifungal activity of Lactobacillus plantarum K35 isolated from traditional Thai fermented rice noodle was evaluated against the growth and aflatoxin production of Aspergillus flavus TISTR304 and Aspergillus parasiticus TISTR3276. Multiple antifungal compounds secreted by L. plantarum were firstly analyzed using GC–MS in parallel to the ultrastructure alteration of the treated fungi. L. plantarum K35 supernatant caused significant reduction of the fungal growth and aflatoxin production. The antifungal activity was pH-dependent and favorable to acidic conditions whereas the catalase treatment had no influence indicating no involvement of hydrogen peroxide in the inhibition. Antifungal substances were resistant to sterilization and proteolytic enzymes including trypsin and proteinase K. The major components, apart from lactic acid, were 2-butyl-4-hexyloctahydro-1H-indene (19.55%), oleic acid (10.52%) and palmitic acid (7.27%). Other minor antifungal compounds included linoleic acid (2.11%), 2,4-di-tert-butylphenol (1.84%), stearic acid (1.55%), 3-phenyllactic acid (1.42%) and pyroglutamic acid (1.07%). The morphological changes of the fungi exposed to the supernatant were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). L. plantarum K35 supernatant caused severe damage to the cell wall and cytoplasmic membrane leading to a massive loss of cytoplasmic content, the formation of membrane-bound vesicles, and complete destruction of membranous organelles including mitochondria and nucleus.     

Effect of water activity and temperature on the growth of Aspergillus flavus,the expression of aflatoxin biosynthetic genes and aflatoxin production in shelled peanuts

The contamination of peanuts with Aspergillus flavus and subsequent aflatoxins is considered to be one of the most serious safety problems in the world. Water activity (a_w) and temperature are limiting factors for fungal growth and aflatoxins production during storage. To optimize the practical storage parameter, the effect of a_w (0.85–0.99) and temperature (15–42 °C) on fungal growth, aflatoxin production and the expression of aflatoxin biosynthetic and regulatory genes in shelled peanuts was investigated. A. flavus grew at a lower rate when temperature ≤20 °C or a_w ≤ 0.85. For the growth of A. flavus in shelled peanuts, the optimum conditions were a_w was 0.98, and the optimum temperature was 37 °C. The maximum amount of AFB₁ in peanuts was obtained at 28 °C and a_w 0.96. Real-time analysis showed that 16 of 25 genes had highest expression levels at 28 °C under a_w 0.92, while 9 genes had highest expression levels at 37 °C under a_w 0.92. Compared with 37 °C, all aflatoxin biosynthetic pathway genes were down-regulated at 42 °C. All the pathway genes and laeA were up-expressed at a_w of 0.96 under 28 °C, compared to a_w 0.99. Furthermore, there was a good positive correlation between the ratio of aflS/aflR and AFB₁ production. The expression of laeA was also positively correlated with AFB₁ production while the expression of brlA was correlated with the A. flavus growth. The results of this study suggest that AFB₁ production in peanut kernels can occur over a wider range of a_w × temperatures levels compared to formula media and peanut media. Previous studies have showed that AFB₁ could not be produced on formula media at 37 °C without the expression of most aflatoxin structural genes. But, in the un-autoclaved shelled peanuts, high concentration of AFB₁ was produced at 37 °C with up-regulation of some aflatoxin biosynthetic genes. From a food safety point of view, the results can be used to optimize certain food technological processes and develop prevention strategies to control such carcinogenic natural metabolites in grains (such as peanuts, maize and rice) and derived products.     

Aflatoxin production by Aspergillus flavus in rumen liquor and its implications

Cow milk in infant and human nutrition is very significant. However, contamination of milk with aflatoxins is considered as a potential risk for human health. Aflatoxin is one of the major etiological factors in the development of hepatocellular carcinoma and is also found in the milk of lactating animals which could have consumed it through contaminated feedstuffs. Thus, exploration to isolate and identify the pathogenic microbe present in the rumen liquor were carried out. The screened fungal organism was identified as Aspergillus flavus by phenotypic (morphology and extrolite profiles) and molecular (β-tubulin gene sequences) characters. Fungal toxin was extracted using immuno-affinity column (IAC) and quantified by High Performance Liquid Chromatography (HPLC). The organism had potential to grow under aerobic and anaerobic conditions and also produce aflatoxin B_1. The aflatoxin B₁ production under aerobic condition was 0.902 ± 0.08 μg/ml culture broth and anaerobic condition was 0.925 ± 0.2 μg/ml culture broth. Aflatoxin B₂ was more compared to aflatoxin B₁ and the quantity was 14.472 ± 1 under aerobic condition and 1.467 ± 0.3 under anaerobic condition. The rumen liquor from which the isolation was carried out also showed the presence of aflatoxin B₁ (3.964 ± 0.5 μg/ml) and B₂ (1.170 ± 0.6 μg/ml). However, aflatoxin G₁ and G₂ were not present. Hence, the study suggests the ability of microbial ecosystem present inside the rumen to produce aflatoxin. This report on the aflatoxin production under aerobic and anaerobic conditions provides insights about the possibility of aflatoxin in cow milk thereby effecting human health. It is vital to reduce exposure of milking animals to contaminated moldy feed and take precautions to prevent fungal contaminations in the feed.     

Aspergillus flavus growth response to cinnamon extract and sodium benzoate mixtures

The effects of selected combinations of cinnamon extract (CE, 0, 50, 100, 200, 400 or 800 ppm) and sodium benzoate (NaB, 0, 12.5, 25, 50, 100, 200, 400 or 800 ppm) on the growth response of Aspergillus flavus inoculated on potato-dextrose agar (PDA) adjusted to 0.98 a_w and pH 3.5 or 4.5 were evaluated for 30 days. Minimal inhibitory concentrations (MIC) were determined, transformed into fractional inhibitory concentrations (FIC) and a FIC_index was computed. Cinnamon extract MIC was 200 ppm and not affected by pH, whereas for NaB a pH reduction from 4.5 to 3.5 reduced the MIC from 800 to 400 ppm. At pH 3.5 additive mixtures included 200 ppm of NaB, whereas at pH 4.5 these mixtures exhibited a synergic effect (FIC_index = 0.75). Mixtures of CE and NaB are promising antifungal agents.     

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.     

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.     

In vitro control of growth and ochratoxin A production by butylated hydroxyanisole in Aspergillus section Nigri species

This study was carried out to determine the efficacy of phenolic antioxidant butylated hydroxyanisole (BHA) under different interacting water activity (a_W) and temperature regimes on the lag phase and growth rate by Aspergillus section Nigri strains. In this experiment four A. section Nigri strains were used. Peanut meal extract agar (PMEA) was prepared at 2%. The a_W of the medium was adjusted to 0.995, 0.980 and 0.930, BHA at 1, 5, 10 and 20 mmol l^?1 was added to the basic medium. The plates were inoculated and incubated for 30 days at 18 and 25 °C. Radial growth rates (mm d^?1) and lag phase (h) were calculated. In control treatments, the growth rate decreased as water activity reduced in all strains assayed. At all a_W levels tested, BHA at 20 mmol l^?1 completely inhibited growth. In general, at 10 mmol l^?1 and 0.995 and 0.980a_W level, a significant reduction respect to control was observed. This antioxidant completely inhibited OTA production, at concentrations of 20 mmol l^?1, regardless of a_W used by all the strains evaluated.     

Inhibition of aflatoxin B1, B2, G1 and G2 production by Aspergillus parasiticus in nuts using yellow and oriental mustard flours

Aflatoxins (AFs) are naturally occurring mycotoxin compounds produced by several species of Aspergillus, as Aspergillus flavus and Aspergillus parasiticus and are mutagenic, teratogenic, and carcinogenic compounds that have been implicated as causative agents in human hepatic and extra hepatic carcinogenesis. In this study, the reduction of the AFs present in dried fruits (peanut, cashew, walnut, almond, hazelnut and pistachio), produced by A. parasiticus CECT 2681, by isothiocyanates (ITCs) generated by the enzymatic hydrolysis of the glucosinolates (GLCs) present in oriental and yellow mustard flours was evaluated. The AFs reduction activity through ITCs application in dried fruits was carried out using a model and food system experiments. The quantification of the AFs in the food products analyzed was carried out employing the technique of the liquid chromatography (LC) coupled to the mass spectrometry detection in tandem (MS/MS). The ITCs produced through GLCs hydrolysis reduced the A. parasiticus growth in the food products tested and in particular in the model system experiments the AFs B₁, B₂, G₁ and G₂ reduction ranged meanly from 83.1 to 87.2% using the oriental mustard flour, whereas employing the yellow flour the mean reduction observed ranged from 27.0 to 32.5%. In the food system experiments carried out employing only the oriental mustard flour the mean AFs reduction observed ranged from 88 to 89%.     

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.     

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 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.     

Combined analytical and microbiological tools to study the effect on Aspergillus flavus of cinnamon essential oil contained in food packaging

Cinnamon essential oil has been used for centuries to protect food from microbiological infection, and in the last ten years cinnamon essential oil is also incorporated into food packaging materials as antimicrobial agent. However, very little is known about the real effect that it has on the microorganism cells. This study combines analytical and microbiological tools to elucidate cell damage produced on Aspergillus flavus. First, antifungal activity of cinnamon essential oil was evaluated at 10³,10⁴, 10⁵ and 10⁶ CFU/mL. Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC) were determined by macrodilution in direct contact with the mold. A strong activity was obtained, with a MIC of 0.05–0.1 mg/mL, and a MFC of 0.05–0.2 mg/mL, both ranges depending on the initial fungal suspensions.Polyethylene terephthalate films containing cinnamon essential oil were tested in vapor phase, without direct contact with the mold. Active PET started showing activity at 2% CIN EO load and produced total inhibition at 4% CIN EO. SEM and FTIR were used to study the cell damage on the mold exposed to the cinnamon essential oil. Evident damage and a strong decrease in sporulation were found by SEM, while biochemical changes in conidia could be suggested from the FTIR spectra analysis. Two deposition techniques were used to prepare the samples for FTIR. The results obtained are shown and discussed.     

Effectiveness of pulsed light treatment for degradation and detoxification of aflatoxin B1 and B2 in rough rice and rice bran

Aflatoxins primarily accumulate in the hull and bran layers of rough rice making these by-products of rice milling unsuitable for animal feed or human consumption. Contaminated rough rice is also a potential source of aflatoxin exposure to workers handling the grain during post-harvest storage and processing. Currently, no technologies are available to remove or detoxify these toxic and mutagenic fungal metabolites from contaminated rough rice. Pulsed light (PL) is a novel technology with the potential to degrade and detoxify aflatoxins in foods and their processing by-products. Rough rice was inoculated with Aspergillus flavus to produce aflatoxin B₁ (AFB₁) and B₂ (AFB₂) contamination, followed by PL treatments of 0.52 J/cm²/pulse for various durations. A PL treatment time of 80 s reduced AFB₁ and AFB₂ in rough rice by 75.0% and 39.2%, respectively; while a treatment time of 15 s reduced AFB₁ and AFB₂ in rice bran by 90.3% and 86.7%, respectively. Since PL treatments result in the degradation of aflatoxins in situ, the toxicity and mutagenic activity of the residual by-products of AFB₁ and AFB₂ after PL treatment were evaluated. Toxicity was estimated using the brine shrimp (Artemia salina) lethality assay and mutagenicity measured by the fluctuation test with Salmonella typhimurum tester strains TA98 and TA100. The mutagenic activity of AFB₁ and AFB₂ was completely eliminated by PL treatment, while the toxicity of these two aflatoxins was significantly decreased. The obtained results suggest that PL technology has a promising potential to degrade, detoxify, and inactivate the mutagenic activity of aflatoxins in rough rice and rice bran.     

Fate of aflatoxin M1 during production and storage of parmesan cheese

The fate of AFM₁ during production of a long maturing cheese (Parmesan cheese) was assessed. Different levels of AFM₁ contamination and of the fat/casein (F/C) ratio of milk were considered, in order to evaluate if these factors can influence the enrichment factor (EF) of AFM₁ in cheese. For this purpose, 24 cheese-makings were carried out using naturally contaminated milk at 3 different AFM₁ levels and at 2 F/C ratios. AFM₁ analysis was performed by HPLC in raw milk, cream, cauldron milk, liquid cattle rennet, whey, curd and cheese at 3, 9, 16 and 24 months of ageing. The mass balances of the cheese-making processes were close to 100%; in whey, AFM₁ concentration was about 40% less than the concentration in cauldron milk. The EF in curd was between 4.0 and 5.2, with an average value of 4.7 ± 0.4; this factor was not significantly affected by either AFM₁ contamination level or F/C ratio. During maturation, AFM₁ concentration and consequently EF increased from curd to 16 ageing months; successively, AFM₁ slightly decreased at 24 months and consequently the EF. At 3, 9, 16 months of maturation, the EF was significantly higher for cheeses prepared using milk with low F/C than those with high F/C milk; on the contrary, EF was not significantly influenced by the AFM₁ contamination level. In cheeses, EF values were between 4.7 and 6.3; from these results, the maximum admissible level for AFM₁ in Parmesan cheese should be about 0.275 μg kg⁻¹.     

Diminution of aflatoxin B1 production caused by an active packaging containing cinnamon essential oil

The antifungal and antimycotoxigenic action of an active package containing cinnamon essential oil have been evaluated against the mold Aspergillus flavus on the aflatoxin B1 production. Two independent experiments were carried out, the first one with cinnamon on a paper diffusion disc placed in vapor phase and the second one with an active PP (Polypropylene) films containing the essential oil. The culture media, exposure time, closure of the Petri dish and cinnamon concentration were evaluated. The first experiment revealed an important reduction on mycotoxin, even when the mold grew, and the action remained for 15 days. The second experiment highlighted the importance of cinnamon concentration on the antimycotoxigenic action, achieving a strong reduction with the sub-inhibitory concentration (2% of cinnamon) and a complete reduction with fungicidal concentration (4% and 6% cinnamon). The UPLC system coupled to a fluorescence detector was optimized for analysis of aflatoxin B1.     

Incidence and consumer awareness of toxigenic Aspergillus section Flavi and aflatoxin B1 in peanut cake from Nigeria

Peanut cake samples were collected from major markets in five states of Nigeria and evaluated for incidence of toxigenic Aspergillus section Flavi populations, and aflatoxin B₁ (AFB₁) levels by liquid chromatography tandem mass spectrometry (LC–MS/MS). The awareness of consumers to the presence of aflatoxin in the snack and potential health risks of its regular ingestion was evaluated by questionnaire analysis. Aspergillus section Flavi populations were recovered from 83% of the peanut cake samples. Aspergillus flavus L-strain was the most predominant (>56%) across the states while Aspergillus tamarii had the least mean incidence (2.7%). The incidence of atoxigenic strains was significantly (p < 0.05) higher than that of toxigenic strains in samples from Lagos and Kaduna, while the toxigenic strains had a significantly (p < 0.05) higher incidence than the atoxigenic strains in Niger. All analyzed cake samples contained AFB₁ in concentrations exceeding the NAFDAC recommended level for AFB₁ in food and reaching up to 2824 μg/kg. There was a weak positive correlation (r = 0.32, p = 0.03) for the relationship between the incidence of toxigenic strains in the samples and AFB₁ concentration. The consumer awareness data showed that 64% of the respondents consumed peanut cake; majority of who are youth of economic and reproductive age. Eighty-five percent of the consumers lacked awareness of aflatoxin contamination in the snack and possible health risks associated with its ingestion.     

Evaluating the combined effect of water activity,pH and temperature on ochratoxin A production by Aspergillus ochraceus and Aspergillus carbonarius οn culture medium and Corinth raisins

The objectives of this study were: (a) to evaluate the potential of the ELISA method in the determination of the produced OTA by Aspergillus ochraceus and Aspergillus carbonarius in malt extract agar (MEA) at different pH (3.9, 5.1, 5.9, 6.8), water activity (a_w) (0.87, 0.93, 0.99), and temperature (10, 15, 20, 25, 30, 40 °C) levels, providing a rapid screening for the optimum and marginal conditions of OTA production, (b) to comparatively evaluate the performance of ELISA and HPLC method, and (c) to evaluate the ability of A. ochraceus to produce OTA in rehydrated Corinth raisins during storage for 36 days. Two independent experiments were carried out to estimate OTA production on MEA and Corinth raisins. The produced OTA was evaluated qualitatively by the ELISA method and selected cases were verified by HPLC. The levels of OTA decreased with water activity, whereas pH seemed to have no specific effect. Furthermore, A. ochraceus produced maximum amounts of OTA on raisins at the 24th day of incubation, indicating that the endogenous microflora may restrictively affect OTA production. The knowledge of optimal and marginal levels of ecological factors in order to optimise post-harvest and storage of food products may significantly affect the production of OTA. Moreover, endogenous microflora of certain foodstuffs may cause OTA detoxification and consequently reduction of OTA levels; a fact that has to be taken into account in food commodities such as raisins, grapes, and wine.     

Effect of sulfur dioxide and ethanol concentration on fungal profile and ochratoxin a production by Aspergillus carbonarius during wine making

Fungal profiles and ochratoxin A (OTA) accumulation during wine making were investigated using five different wine grape cultivars, Cabernet Sauvignon, Pinot Noir, Merlot, Syrah and Petit Verdot and the intrinsic influences caused by sulfur dioxide, ethanol and combine effect of ethanol and reducing sugar were analyzed using Cabernet Sauvignon and inoculation of Aspergillus carbonarius. Aspergillus spp. and Penicillium spp. were found as the major fungi in all winemaking processes and were highly correlated with OTA accumulation in wine. Most fungi died and OTA production decreased after 48 h of alcoholic fermentation, being consistent with the period when ethanol accumulation increased. The addition of SO₂ significantly inhibited the growth and OTA production of A. carbonarius with complete inhibition at 500 mg/L. When the ethanol concentration in the must increased to the range of 2–4%, growth and OTA production of A. carbonarius were significantly inhibited. Reducing sugar concentration had no significant effect on the growth and OTA production of A. carbonarius within the levels changing during the winemaking. Therefore, the increase of ethanol concentration played an important role in causing the decrease of fungal contamination and OTA accumulation during winemaking.