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.     

Mycotoxin occurrence in corn meal and flour traded in São Paulo,Brazil

In the present study, 60 samples of corn meal and flour traded in São Paulo were analysed for determination of aflatoxins and fumonisins B₁ (FB₁) and B₂ (FB₂). No aflatoxin was found in samples of both products. In corn meal, the concentrations of FB₁ and FB₂ ranged from 1.1 to 15.3 mg kg⁻¹ (mean: 5.2 mg kg⁻¹) and 0.2 to 3.9 mg kg⁻¹ (mean: 1.0 mg kg⁻¹), respectively. Corn flour presented lower levels of FB₁ (0.5–7.2 mg kg⁻¹; mean: 2.1 mg kg⁻¹) and FB₂ (0.1–1.8 mg kg⁻¹; mean: 0.7 mg kg⁻¹). Considering the average values of FB₁ found in corn meal samples, as well as food consumption estimates in Brazil, the worst case of FB₁ consumption would be 2.9 μg kg body weight⁻¹ per day. Results indicate the need for the adoption of practices to control the occurrence of fumonisins by manufacturers of corn products, mainly in corn meal.     

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.     

Fungal contamination and aflatoxin B1 of ‘egusi’ melon seeds in Nigeria

One hundred and thirty seven samples of melon seeds (Colocynthis citrullus L.) from randomly selected farmers’ stores in the humid forest and Northern Guinea savanna of Nigeria were analysed for the incidence of diseased seeds, moisture content, associated moulds and levels of aflatoxin B₁ contamination. The proportion of diseased seeds ranged from 2.5 to 37.3% in the forest and 2.1 to 17.9% in the savanna, while the seed moisture content varied from 5.3 to 10.4%, and 4.6 to 9.5% respectively. All the samples contained moulds, with the two genera, Aspergillus and Penicillium predominating, while A. flavus had the highest species count. The other common fungal isolates in order of decreasing incidence were A. niger, P. citrinum, Botryodiplodia theobromae, Cladosporium sp and A. clavatus. Thin layer chromatography analysis showed that 32% in the forest and 21% samples in the savanna contained aflatoxin B₁ with mean levels of 14.8 μg/kg in the forest and 11.3 μg/kg in the savanna respectively. Significant positive correlations were found between number of aflatoxin B₁ positive samples and the percentage of A. flavus infected samples and between the levels of diseased seeds and the levels of aflatoxin B₁ contamination.     

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.     

Aflatoxins in rice – A limited survey of products marketed in Austria

Eighty-one rice samples were purchased from different markets in Vienna and were analysed for their aflatoxin content. The samples were extracted using methanol in water (80/20 v/v) followed by immunoaffinity clean up. The determination was carried out by HPLC–FLD coupled to a Kobracell. Different samples including basmati rice, whole grain rice, long grain rice, short grain rice as well as puffed rice were investigated. Moreover, conventionally and organically produced rice were compared. The results revealed that 24 out of 81 samples contained detectable amounts of aflatoxins. Aflatoxin B₁ could be quantified in 15 samples and aflatoxin B₂ in one sample. The contamination range was noted to be between 0.45 μg kg⁻¹ and 9.86 μg kg⁻¹ for aflatoxin B₁ and 1.5 μg kg⁻¹ for aflatoxin B₂. Aflatoxins G₁ and G₂ were not detected in any sample. Three samples exceeded the maximum levels set in the European Union; having AFB₁ concentrations of 2.16, 2.85 and 9.86 μg kg⁻¹. In the three organic produced rice samples only traces of aflatoxins were found.     

Occurrence of AFM1 in urine samples of a Brazilian population and association with food consumption

This survey evaluated the presence of AFM₁ in human urine samples from a specific Brazilian population, as well as corn, peanut, and milk consumption measured by two types of food inquiry. Urine samples from donors who live in the city of Piracicaba, State of São Paulo, Brazil were analyzed to detect the presence of aflatoxin M₁ (AFM₁), an aflatoxin B₁ metabolite, which may be used as aflatoxin B₁ exposure biomarker. The AFM₁ analysis was performed using immunoaffinity clean-up and detection by high-performance-liquid chromatography with fluorescence detector. A total of 69 samples were analyzed and 45 of them (65%) presented contaminations ⩾1.8 pg ml⁻¹, which was the limit of quantification (LOQ). Seventy eight percent (n = 54) of the samples presented detectable concentrations of AFM₁ (>0.6 pg ml⁻¹). The AFM₁ concentration among samples above LOQ ranged from 1.8 to 39.9 pg ml⁻¹. There were differences in food consumption profile among donors, although no association was found between food consumption and AFM₁ concentration in urine. The high frequency of positive samples suggests exposure of the populations studied to aflatoxins.     

Aflatoxin B1 and ochratoxin A in breakfast cereals from athens market: Occurrence and risk assessment

A method for aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) determination in breakfast cereals is described using a simultaneous methanolic-aqueous extraction followed by immunoaffinity columns clean-up step and High Pressure Liquid Chromatography (HPLC) with Fluorescence Detector (FD). Recoveries were found to be 78% and 83% for AFB₁ and OTA, respectively, while the detection limit (DL) was 0.02 ng g^?1 for both mycotoxins. Both determinations were applied in fifty five samples of breakfast cereals purchased from Athens market. Results revealed the presence of AFB₁ in 56.3% of the samples examined (mean 1.42 ng AFB₁ g^?1). Seven samples (median 3.5 ng AFB₁ g^?1) were found to be contaminated at levels higher than the EU limit (2 g g^?1). OTA was detected in 60% of the samples (mean 0.18 ng g^?1). Nineteen samples were found to be contaminated by both mycotoxins. In addition in the present study the daily exposure to AFB₁ and OTA is discussed.     

The effect of the association of sanitizers and surfactant in the microbiota of the Cantaloupe (Cucumis melo L.) melon surface

This work aimed to evaluate the efficiency of 200, 500 and 1000 mg l⁻¹ of free available chlorine (FAC) and 60 mg l⁻¹ of peracetic acid (APA) associated or not with Tween 80 in reducing the mesophilic aerobes, coliforms group and fecal coliforms on cantaloupe melon surface. Also, the action of the organic chloramine in removing the Salmonella enteritidis when attached on the melon surface. All treatments reduced significantly (p<0.05) the microbiota analyzed when compared with a water washing, used as control. The treatment with 1000 mg l⁻¹ of organic chloramine with surfactant reduced the mesophilic aerobes (p<0.05) by 4-log cycles, more than the control. Also this chlorine solution was the most efficient in removing S. enteritidis after attachment of the microorganisms to the fruit surface, between 1 and 24 h.     

Amperometric biosensor for aflatoxin B1 based on aflatoxin-oxidase immobilized on multiwalled carbon nanotubes

An amperometric aflatoxin biosensor developed by aflatoxin-oxidase (AFO), embedded in sol-gel, linked to multiwalled carbon nanotubes (MWCNTs)-modified Pt electrode was reported for the first time. The covalent linkage between AFO and MWCNTs retained enzyme activity and responsed to the oxidation of afltoxin B₁ (AFB₁). Its apparent Michaelis-Menten constant for AFB₁ was 7.03 μmol·L^?1, showing a good affinity. The sensor exhibited a linear range from 3.2 nmol·L^?1 to 721 nmol·L^?1 (1 ng/ml to 225 ng/ml) with limits of detection of 1.6 nmol·L^?1 (signal-to-noise ratio = 3), an average response time of 44 s (less than 30 s when AFB₁ Conc. is bigger than 45 ng/ml), and a high sensitivity of 0.33 × 10² A mol^?1·L cm^?2. The active energy was 18.8 kJ mol^?1, demonstrating the significant catalyzation of AFO for oxidation of AFB₁ in this biosensor.     

Potential of botanicals and biocontrol agents on growth and aflatoxin production by Aspergillus flavus infecting rice grains

The potential of certain plant extracts and biocontrol agents for the reduction of aflatoxin B₁ (AFB1) in stored rice was investigated. Among the plant extracts tested, Syzigium aromaticum (5 g/kg) showed complete inhibition of Aspergillus flavus growth and AFB1 production. Curcuma longa, Allium sativum and Ocimum sanctum also effectively inhibited the A. flavus growth (65–78%) and AFB1 production (72.2–85.7%) at 5 g/kg concentration. Among the biocontrol agents, culture filtrate of Rhodococcus erythropolis completely inhibited the AFB1 production at 25 ml/kg concentration. The other biocontrol agents, Pseudomonas fluorescens, Trichoderma virens and Bacillus subtilis showed 93%, 80% and 68% reduction of A. flavus growth and 83.7%, 72.2% and 58% reduction of AFB1 at 200 ml/kg, respectively.     

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.     

Control of Fusarium moulds and fumonisin B1 in seeds by gamma-irradiation

The distribution of naturally occurring Fusarium moulds producing fumonisin B₁ in seeds was determined. Fusarium infection of seed samples ranged from 10% to 60%, Fusarium moniliforme was the predominant species. Fusarium counts in wheat seeds were 8.1 × 10⁴ CFU/g, 6.3 × 10⁶ CFU/g in maize and 4.8 × 10³ CFU/g in barley. Wheat, maize and barley seeds naturally contaminated with varying levels of fumonisin B₁ 1.4–5.8, 8.0–13.8 and 0.1–0.5 μg/g, respectively. F. moniliforme and Fusarium proliferatum were major Fusarium contaminants producing fumonisin B₁. The effect of gamma irradiation on Fusarium moulds and levels of fumonisin B₁ was also determined. The viable counts of Fusarium in seeds decreased by increasing the radiation dose levels and the growth of Fusarium spp. was inhibited at 4.0 kGy for barley and 6.0 kGy for wheat and maize. Application of radiation dose at 5 kGy inactivated fumonisin B₁ by 96.6%, 87.1% and 100% for wheat, maize and barley, respectively, and a dose of 7 kGy was sufficient for complete destruction of fumonisin B₁ in wheat and maize.     

A rapid FT-NIR method for estimation of aflatoxin B1 in red chili powder

The feasibility of measuring Aflatoxin B₁ (AFB₁) in red chili powder was investigated by using Fourier transform near-infrared (FT-NIR) spectroscopy in diffuse reflectance mode combined with appropriate chemometric techniques. Aflatoxin free chili powder samples were spiked with known amount of AFB₁ ranging from 15 to 500 μg/kg and used for calibration model building based on partial least squares (PLS) regression algorithm. Different spectral preprocessing methods were investigated and optimized based on the lowest values of root mean square error of cross validation (RMSECV). Spectral wavenumber range of 6900.3–4998.8 and 4902.3–3999.8 cm^?1 and straight line subtraction preprocessing technique predicted AFB₁ content with best accuracy with lowest RMSECV = 0.654% and maximum correlation coefficient for validation plots (R² = 96.7). The overall results demonstrate that FT-NIR spectroscopy can be used for rapid, non destructive quantification of Aflatoxin B₁ in red chili powder.     

Validation of the procedure for the determination of aflatoxin B1 in animal liver using immunoaffinity columns and liquid chromatography with postcolumn derivatisation and fluorescence detection

The validation of the procedure for the determination of aflatoxin B₁ in animal liver (pig, chicken, turkey, beef, calf) was performed. The limit of detection (LOD) and limit of quantification (LOQ) were 2 ng/kg and 7.8 ng/kg, respectively. The repeatability of measurements, represented by the standard deviation (RSD_r) was 7.5%, 7.1%, and 4.8% at the contamination levels of 0.025 μg/kg, 0.050 μg/kg, and 0.075 μg/kg, respectively. The relative standard deviation for the within-laboratory reproducibility (RSD_R) was 18% at the level of 0.025 μg/kg and 22% at the levels of 0.050 μg/kg and 0.075 μg/kg. The measurement uncertainties at the same contamination levels were ±0.007 μg/kg, ±0.016 μg/kg, and ±0.023 μg/kg, respectively. The mean recovery was 72.8%, the decision limit (CCα) 0.063 μg/kg and the detection capability (CCβ) 0.080 μg/kg. The results indicate that the procedure is suitable for the determination of aflatoxin B₁ in animal liver and can be implemented for the routine analysis.     

Degradation of aflatoxins in aqueous buffer in the presence of nucleophiles

This study compared the efficacies of lysine, glycine and methylamine to mediate aflatoxin destruction in heated aqueous phosphate buffers. A 3 × 3 × 4 factorial design (buffer pH, heating temperature and nucleophile) was followed. The buffer was artificially contaminated (“spiked”) with mixed aflatoxin standard and heated for specified time periods. After the heat treatment residual aflatoxins were determined using HPLC procedures.Aflatoxin reduction was influenced by the buffer pH and the pK_a of the added nucleophile. When phosphate buffer (at pH 9) was heated to 150 °C the degradation rate constants (k) aflatoxin in the presence of lysine, glycine and methylamine were 0.11, 0.09 and 0.08 min⁻¹ respectively. Addition of calcium chloride to the “spiked” buffer lowered aflatoxin reduction, but upon adding lysine or methylamine, aflatoxin reduction was restored to some extent. These findings demonstrate the potential capability of lysine to mediate aflatoxin reduction.     

Effects of pulsed electric field treatments on quality of peanut oil

The effects of pulsed electric fields (PEF) treatment on physicochemical properties of peanut oil were investigated in this paper. Compositions of fatty acid, acid value (AV), peroxide value (PV), as well as carbonyl group value (CGV) of various PEF-treated peanut oil samples with different storage time were determined by GC/MS and AOCS standard methods. GC/MS analysis showed that little change of the oil composition was observed after PEF treatment. However, after being treated by various PEF treatments and stored at 40 °C for 100 days, the biggest increment of AV was 0.69 mg g⁻¹, which was lower than that of untreated peanut oil (0.79 mg g⁻¹). The PV significantly increased from 4.8 meq kg⁻¹ untreated oil to 11.5 meq kg⁻¹ PEF treated oil (50 kV cm⁻¹). And the increase extent of CGV of oil samples during the 100 d’ storage period was decreased with increasing electric field strength. During the storage period, the differences of AV, PV, and CGV of PEF-treated sample during storage period were less than that of untreated oil, which implied that the PEF treatment could restrain the speed of lipid oxidation reaction thus extending the shelf-life of oil rich products.     

Occurrence of aflatoxin B1 in food products derivable from ‘egusi’ melon seeds consumed in southwestern Nigeria

Aflatoxin, the toxic secondary metabolite of Aspergillus flavus and Aspergillus parasiticus has been considered as one of the most serious food safety problems in sub Saharan Africa. Egusi melon seeds is susceptible to these fungal infection during postharvest. Therefore, the content of aflatoxin B1 in three food products derivable from ‘egusi’ melon seeds ogiri’ (fermented melon seed condiment), ‘robo’ (melon ball snacks) and egusi soup destined for human consumption in Nigeria in 2005 and 2006 were determined. Aflatoxin B1 was analysed by thin layer chromatography (TLC) with fluorescent detection. The percentage of samples positive for aflatoxin B1 were for 25% robo, 31.8% for ogiri, and 19.5% for ‘egusi’ soup. Aflatoxin B1 ranged from 2.3 to 15.4 ppb in all samples. The overall mean levels of aflatoxin B1 were for 8.9 ppb for ogiri, 9.7 ppb for ‘robo’ and 7.2 ppb for ‘egusi soup’. All positive melon seeds derived food products analysed in this study contained aflatoxin B1 at concentrations much lower than the 20 ppb permissible limit recommended in Nigerian food and suggests that melon seed derived foods present less risk by human exposure to aflatoxin through their consumption. However, it is important to consider these levels in terms of their contribution to overall daily exposure to aflatoxin levels in food. This is the first report of aflatoxin determination in melon seed food products.     

Mycotoxin occurrence in beer produced in several European countries

The occurrence of ochratoxin A, trichothecenes, fumonisins and aflatoxins in a sample of 106 beers produced in several European countries, was investigated. The analyses were conducted using high-performance liquid chromatography with fluorimetric detection for ochratoxin A and aflatoxins, gas-chromatography and high-performance liquid chromatography, both coupled with mass spectrometer, for trichothecenes and fumonisins, respectively. Aflatoxins were not detected in any samples, whereas ochratoxin A, deoxynivalenol and fumonisins were found in a relatively high number of samples. Their presence was at low levels in all samples; however, some differences were observed between the European countries. As regards ochratoxin A, beer samples from southern Europe showed levels always lower than 0.040 μg l^?1, while the samples from other European countries showed significantly higher values, up to 0.189 μg l^?1 (P < 0.001). For fumonisins, the levels of Italian beers were significantly higher compared to the samples from other countries (P = 0.006).     

Survey of aflatoxin B1 in helva,a traditional Turkish food,by TLC

A total of 102 helva samples consisting of 34 plain helva, 34 helva containing cacao, and 34 helva containing pistachio nuts purchased from helva-factories and supermarkets in Adana of Turkey were analysed for aflatoxin B₁ (AFB₁) by thin-layer chromatography. The detection limit of AFB₁ was 1 μg kg⁻¹. Recovery experiments were carried out with spiked samples in the range 2–10 μg kg⁻¹ of AFB₁. No AFB₁ was found in any plain helva and helva containing cacao samples. On the other hand, of 34 helva containing pistachio nuts AFB₁ was determined in eight samples. AFB₁ was found in excess of Turkish legal limit of 5 μg kg⁻¹ in 4 of 102 helva samples. This paper reports the data of the first survey for the presence of AFB₁ in helva in Turkey.