Investigations on the essential oil of Lippia rugosa from Cameroon for its potential use as antifungal agent against Aspergillus flavus Link ex. Fries

Lippia rugosa essential oil was tested for its effectiveness against Aspergillus flavus on artificial growth media. The chemical composition of the oil was determined by gas chromatography–mass spectrometry (GC–MS). Geraniol (51.5%), nerol (18.6%) and geranial (10.4%) were the main components of Lippia oil. After 8 days of incubation on essential oil supplemented medium, mycelium growth of A. flavus was totally inhibited by 1000 mg l^?1 of L. rugosa essential oil. The effect of essential oil on aflatoxin B₁ synthesis was evaluated in SMKY broth. The medium supplemented with different essential oil concentrations, was inoculated with A. flavus mycelium and incubated at 25 °C. After 2, 4, 6 and 8 days, aflatoxin B₁ (AFB₁) was quantified in the supernatant using Enzyme Linked Immuno-Sorbent Assay (ELISA). Results showed that aflatoxin B₁ synthesis was inhibited by 1000 mg l^?1 of L. rugosa essential oil after 8 days of incubation. The effect of the EO on the H⁺-ATPase pumping membrane was also evaluated in the presence of several concentrations of oil (200–2000 mg l^?1) by monitoring glucose-induced acidification of the external medium. L. rugosa essential oil at the concentration of 2000 mg l^?1 completely inhibited the activity of this enzyme. These data suggest that the essential oil of L. rugosa is a fungicidal for A. flavus and its possible cellular target include the H⁺-ATPase.Results obtained in the present study indicate the possibility of exploiting Lippia rugosa essential oil in the fight against strains of A. flavus responsible for biodeterioration of stored foods products.     

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.     

Microorganisms associated with the spoilage of Pupuru

This study involved evaluation of physicochemical and microbiological changes in dried Pupuru (fermented, smoke dried cassava) balls under storage conditions simulating those currently used by the traditional processors. The aim was to understand the process of spoilage with a view to reducing the rate. pH ranged from 3 to 4, reducing significantly in cabinet-dried samples from 4.24 to 3.27 after 6 days of storage. Viable counts were in the range of 6–8 log cfu/g. Spoilage microorganisms included aerobic spore-forming and non-sporing bacteria as well as potentially toxigenic moulds like Aspergillus flavus and Penicillium species, which could constitute a health hazard to consumers.     

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.     

Changes in the concentration of aflatoxin M1 during manufacture and storage of White Pickled cheese

In this study White Pickled cheese was produced from cow’s milk contaminated artificially with aflatoxin M₁ (AFM1) at two different levels, 1.5 and 3.5 μg/kg (ppb), and the effects of process stages on the AFM1 contents were investigated. Pasteurization at 72 °C for 2 min caused losses of AFM1 about 12% and 9%, respectively, in milk contaminated with 1.5 μg/kg AFM1, and 3.5 μg/l AFM1. These losses were found to be statistically significant (P < 0.01). After the cheese production, about 56% and 59% of total AFM1 remained in cheese–curd while about 32% of total AFM1 transferred to the whey for both 1.5 μg/kg and 3.5 μg/kg AFM1 contaminated milk. After 3-month storage in brine, AFM1 content of cheeses produced from 1.5 and 3.5 μg/kg AFM1 contaminated milks decreased by 2.9% and 2.8%, respectively. Changes in AFM1 content of cheese samples were found statistically insignificant (P > 0.05 and P > 0.01) for 3-month storage periods.     

Incidence of zearalenone and fumonisins in Bulgarian cereal production

Ninty-one small-grain cereals (wheat, barley, maize) collected during the 2007 harvest in Bulgaria were tested for zearalenone (ZON) and fumonisins contamination. Analytical methods based on immunoaffinity clean-up and detection by liquid chromatography was used after validation. Limits of detection for ZON in different matrices were below 4.0 μg/kg in barley and wheat, and slightly higher for maize (17.6 μg/kg). The limit of quantification for ZON was 12 μg/kg in barley and wheat, and 58.8 μg/kg in maize. Recovery values ranged between 84% and 105%. The occurrence of ZON in cereals were rather low and only single incidences was found – up to 148 μg/kg for maize and 36.6 μg/kg for other cereals. Fumonisins in maize have showed a widespread distribution (in 94.7% of tested samples). One of the tested samples was contaminated above the established maximum limits for unprocessed maize.     

Effect of combined physico-chemical treatments based on enterocin AS-48 on the control of Listeria monocytogenes and Staphylococcus aureus in a model cooked ham

Enterocin AS-48 was tested alone or in combination with chemical preservatives and/or heat against Listeria monocytogenes and Staphylococcus aureus in a cooked ham model system. AS-48 (20, 40 and 60 μg g⁻¹) alone was active against L. monocytogenes at 5 and 15 °C, but it was not sufficient to avoid regrowth of Listeria during the 60 days storage. Combination of AS-48 (40 μg g⁻¹) with nitrite/nitrate, pentasodium tripolyphosphate, sodium benzoate or potassium sorbate improved the anti-listeria effect during storage at 5 °C. The most effective combination was AS-48-nitrite/nitrate (0.007%) that reduced listeria below detection level from the beginning to end of storage. Although much more resistant, S. aureus was also inhibited by AS-48 alone at 5 °C, and especially in combinations with nitrite/nitrate, pentasodium tripolyphosphate, sodium lactate and sodium acetate. Best results against both pathogens were obtained when sodium pyrophosphate was applied in combination with 60 μg g⁻¹ AS-48. Sub-lethal heat (60 °C, 2 min) clearly increased AS-48 activity against both Listeria and Staphylococcus.     

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.     

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.     

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.     

Preventive effect of tannic acid in combination with modified atmospheric packaging on the quality losses of the refrigerated ground beef

Chemical, microbiological and sensorial changes of ground beef treated without and with tannic acid (200 mg/kg) and stored in air and under modified atmosphere packaging (MAP) (80%O₂/20%CO₂ or 10%O₂/20%CO₂/70%N₂) were monitored during 15 days of storage at 4 °C. During the storage, samples treated with tannic acid and kept under all packaging conditions contained lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with coincidental lower non-haem iron content, compared with non-treated counterparts (P < 0.05). The sample packed in high oxygen MAP treated without and with tannic acid had the higher oxymyoglobin and a^* values and received the higher likeness scores for colour, whereas the samples stored in air and under low oxygen MAP showed the lower values, regardless of tannic acid treatment. After 15 days of storage, myosin heavy chain (MHC) and actin of all tannic acid treated samples underwent less degradation than those without tannic acid treatment for all packaging conditions. Degradation of MHC was more pronounced in samples kept under MAP with high oxygen. Psychrophilic bacterial count (PBC) of all tannic acid treated samples was lower, compared with that of non-treated samples (P < 0.05), irrespective of packaging condition. Therefore, tannic acid treated samples stored under high oxygen MAP could maintain the red colour and retard lipid oxidation and microbial growth of ground beef during refrigerated storage.     

Aflatoxin M1 contamination in dairy products marketed in Iran during winter and summer

In the present study, 298 dairy product samples consisting of pasteurized milk (91 samples), yoghurt (68 samples), white cheese (72 samples), butter (31 samples) and ice cream (36 samples) collected from popular markets in four large Iranian cities were examined for aflatoxin M₁ (AFM₁) by thin layer chromatography (TLC) technique. The toxin was detected in 66 (72.5%) pasteurized milk samples (mean: 0.052 μg/l; range: 0.013–0.250 μg/l), 45 (66.1%) yoghurt samples (mean: 0.032 μg/kg; range: 0.015–0.119 μg/kg), 59 (81.9%) white cheese samples (mean: 0.297 μg/kg; range: 0.030–1.200 μg/kg), 8 (25.8%) butter samples (mean: 0.005 μg/kg; range: 0.013–0.026 μg/kg) and 25 (69.4%) ice cream samples (mean: 0.041 μg/kg; range: 0.015–0.132 μg/kg). The concentration of AFM₁ in 36.2%, 20.6%, 30.5%, 9.6% and 27.7% of pasteurized milk, yoghurt, white cheese, butter and ice cream samples, respectively, were higher than Iranian national standard limits. Levels of AFM₁ in samples of pasteurized milk, yoghurt, butter and ice cream collected in winter were significantly higher (P < 0.05) than those collected in summer. In the case of white cheese, level of AFM₁ was higher in winter than in summer, but the difference was not statistically significant (P > 0.05). The results indicated that the contamination of the dairy products in such a level could be a serious public health problem at the moment.     

Trace element levels of mushroom species from East Black Sea region of Turkey

The levels of trace metals of mushroom samples collected from East Black Sea region of Turkey were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion method. The accuracy of the method was corrected by standard reference material (NIST SRM 1573a Tomato Leaves). The contents of investigated trace metals in mushroom samples were found to be in the range of 18.9–64.8 μg/g for copper, 53.5–130 μg/g for manganese, 44.7–198 μg/g for zinc, 187–985 μg/g for iron, 0.54–10.8 μg/g for selenium and 0.9–2.5 μg/g for cadmium. Mushrooms species in the highest levels of trace elements were found Entoloma sinuatum for Cu and Zn, Leucoagaricus leucothites for Mn, Amanita pantherina for Fe and Se, Agaricus arvensis for Cd.     

Incidence and level of patulin contamination in pure and mixed apple juices marketed in Italy

A survey on the occurrence of patulin was conducted during 2005 on commercial pure apple juices (53 samples) and mixed apple juices (82 samples) marketed in Italy. The current study was undertaken to investigate the possible influence of the agro-food production process employed (conventional or organic), of the fruit percentage in the commercial product (higher or lower than 50%) and of the type of apple juice (clear or cloudy) on the occurrence and level of patulin contamination. Patulin could be quantified in 34.8% of the samples ranging from 1.58 to 55.41 μg kg⁻¹. With the exception of one sample, the level of patulin was lower than 50 μg kg⁻¹, the maximum permitted threshold in fruit juices according to the European legislation. Mean levels of patulin were significantly lower in mixed apple juices (4.54 μg kg⁻¹) than in pure apple juices (9.32 μg kg⁻¹). Levels of patulin contamination were comparable in clear and cloudy juices. A similar incidence of positive samples was found in conventional and organic apple based juices, and the magnitude between the mean contamination levels, although higher in organic (10.92 μg kg⁻¹) than in conventional juices (4.77 μg kg⁻¹), was not statistically significant (p = 0.771; Mann–Whitney test). The magnitude between the means of patulin contamination in juices containing more than 50% fruit (11.26 μg kg⁻¹) and in juices with 50% or less fruit (3.35 μg kg⁻¹) was statistically significant (p = 0.016; Mann–Whitney test).     

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.     

Effect of packaging and storage conditions on quality of shelled walnuts

The present study investigated the effect of packaging and storage conditions on quality of raw shelled walnuts. Walnut kernels were packaged in: (a) low density polyethylene (LDPE), 55 μm in thickness in air, (b) polyethylene terephthalate||polyethylene (PET||PE), 70 μm in thickness under N₂, and (c) PET-SiO_x||PE pouches, 62 μm in thickness under N₂. Samples were stored either under fluorescent light or in the dark at 4 or 20 °C for a period of 12 months. Quality parameters monitored were peroxide value (PV), hexanal, 2-thiobarbituric acid (TBA), odor, and taste of product. PV ranged between 0.3 for fresh walnut kernels and 31.4 meq O₂/kg oil for walnuts packaged in PE pouches exposed to light after 12 months of storage. Respective values for hexanal were <28.5 μg/kg and 36.0 mg/kg and for TBA ca. 0.2 and 11 mg MDA/kg. Values for odor ranged between 0.2 for fresh walnut kernels and 5.7 for walnut kernels packaged in PE exposed to light after 12 months of storage at 20 °C. Respective values for taste were 0.7 and 6.8. Taste proved to be a more sensitive attribute than odor. Based on shelf life (taste) values and PV data it is proposed that the upper limit value for PV is close to 10.0 meq O₂/kg walnut oil. Respective limit values for hexanal are 1–2 mg hexanal/kg walnut and for TBA is 1–2 mg malondialdehyde/kg walnut. Walnuts retained acceptable quality for ca. 2 months in PE-air, 4–5 months in PET||PE-N₂ and at least 12 months in PET-SiO_x||PE-N₂ pouches at 20 °C, with samples stored in the dark retaining slightly higher quality than those exposed to light. The effect of parameters investigated followed the sequence: temperature > degree of O₂ barrier > lighting conditions.     

High hydrostatic pressure treatment applied to model cheeses made from cow’s milk inoculated with Staphylococcus aureus

Pasteurized milk was inoculated with two strains of Staphylococcus aureus (CECT4013 or ATCC13565) and used to elaborate soft-curd cheeses with approximately 7.5-log CFU/g of S. aureus. Cheeses were submitted to 10 min high hydrostatic pressure (HHP) treatments of 300, 400 or 500 MPa at 5 °C or 20 °C. Staphylococcus enterotoxin (SE) was evaluated in cheeses containing ATCC13565. Counts of S. aureus were measured after HHP treatment (day 1) and after 2, 15 and 30 days ripening at 8 °C. Inactivation increased with pressure and storage time, but was similar for both treatment temperatures. Maximum S. aureus reductions were achieved after 30 days ripening for samples treated at 500 MPa and 5 °C: 6.0 ± 0.1 and 4.7 ± 0.5-log CFU/g for CECT4013 and ATCC13565, respectively. However, SE was detected in all cheese samples containing ATCC13565 before and after HHP and after 30 days ripening.     

Effects of Zataria multiflora Boiss. essential oil and nisin on Bacillus cereus ATCC 11778

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO, 0.0%, 0.005%, 0.015%, 0.03% and 0.045%) and nisin (N, 0.0, 0.25, 0.5, 1.5 and 2.5 μg ml⁻¹), pH values (7.4, 6.5 and 6.0), temperatures (Ts, 10, 20 and 30 °C) and storage times (Ds, up to 43 days) on log₁₀ probability percentage of growth initiation (log P%) of one vegetative cell of Bacillus cereus in brain heart infusion broth were evaluated in a factorial design study. The log P% of the organism was significantly affected (P < 0.01) by the values of EO, N, pH, T and D.The combinations of T ⩾ 20 °C, EO ⩽ 0.03% and pH values (7.4, 6.5 and 6.0) could not obviously affect the growth of the organism in this study. Whereas, the strong inhibitory action was observed by increasing EO concentration to 0.045 at T ⩾ 20 °C and selected pH values (7.4, 6.5 and 6.0) and by decreasing temperature to 10 °C at EO ⩾ 0.015% and pH values used in this study. The inhibitory effect of N also was enhanced by decreasing storage temperature to 10 °C at the selected pH values (7.4, 6.5 and 6.0) in this study.The growth of the organisms was strongly affected by increasing EO concentration to 0.03% in combination with N concentrations used at the selected temperatures in this study. The growth of the organism was completely inhibited at combinations EO ⩾ 0.015%, N ⩾ 1.5 μg ml⁻¹, T ⩽ 30 °C and pH ⩽ 7.4 during 43 days of storage in this study. This synergistic effect of EO and N was enhanced in lower pH values (6.5 and 6.0) in the present study. The growth of organism was completely inhibited at combinations of EO ⩾ 0.005 and N ⩾ 1.5 μg ml⁻¹ at pH = 6.0, and EO ⩾ 0.03 and N ⩾ 0.5 μg ml⁻¹ at pH ⩽ 6.5 during the study at the selected Ts (30, 20 and 10 °C).     

Occurrence of aflatoxin M1 in raw milk in South Korea using an immunoaffinity column and liquid chromatography

The level of aflatoxin M₁ (AFM₁) contamination in raw milk produced in South Korea was investigated using immunoaffinity column chromatography and high performance liquid chromatography with fluorescence detector. A total of 100 raw milk samples were collected from 100 cattle ranches located in three different provinces of South Korea. Forty eight out of 100 raw milk samples contained AFM₁ at low level (0.002–0.08 μg/L) with mean value of 0.026 μg/L. Among the AFM₁ contaminated samples, 29 raw milk samples contained only traceable amount of AFM₁ below the limit of LOQ, 0.02 μg/L. None of samples exceeded the maximum level (0.5 μg/L) of Korean regulation for AFM₁ in milk. The limit of detection was 0.002 μg/L. The result of recovery test with 0.5 μg/L AFM₁ in raw milk sample was 96.3% (SD 3.6, n = 5). This is the first pioneering study to investigate the level of AFM₁ in raw milk used in dairy industries in South Korea.     

Monitoring the occurrence of genetically modified soybean and maize in cultivated fields and along the transportation routes of the Incheon Port in South Korea

In South Korea, imported genetically modified (GM) soybean and maize have been approved for both human consumption and use in animal feed, but not for use in cultivation in fields. This study was conducted to survey the spread of GM soybean and maize in South Korea using multiplex-PCR analysis methods. Cultivated soybean, wild soybean, and maize leaf samples were collected from 26 major areas of soybean cultivation throughout eight provinces. Roadside areas near a major grain port in Incheon were also surveyed to investigate the escape and spread of GM seeds and plants. Amplification results showed that no GM soybean or maize was collected from cultivated fields. However, four GM maize plants were found in samples collected from the roadside near a grain transporting company at the Incheon Port. Based on PCR analysis using GM maize event-specific primers, it was suggested that a maize plant may be Mon810, while the other plants may be stacked events: Mon863 × Mon810 or Mon88017 × Mon810.