Mycobiota and mycotoxins of almonds and chestnuts with special reference to aflatoxins

Several secondary metabolite gene clusters in the genomes of ten Penicillium spp. raise the risk of multiple mycotoxin occurrence in chestnuts

Penicillium spp. produce a great variety of secondary metabolites, including several mycotoxins, on food substrates. Chestnuts represent a favorable substrate for Penicillium spp. development. In this study, the genomes of ten Penicillium species, virulent on chestnuts, were sequenced and annotated: P. bialowiezense. P. pancosmium, P. manginii, P. discolor, P. crustosum, P. palitans, P. viridicatum, P. glandicola, P. taurinense and P. terrarumae. Assembly size ranges from 27.5 to 36.8 Mb and the number of encoded genes ranges from 9,867 to 12,520. The total number of predicted biosynthetic gene clusters (BGCs) in the ten species is 551. The most represented families of BGCs are non ribosomal peptide synthase (191) and polyketide synthase (175), followed by terpene synthases (87). Genome-wide collections of gene phylogenies (phylomes) were reconstructed for each of the newly sequenced Penicillium species allowing for the prediction of orthologous relationships among our species, as well as other 20 annotated Penicillium species available in the public domain. We investigated in silico the presence of BGCs for 10 secondary metabolites, including 5 mycotoxins, whose production was validated in vivo through chemical analyses. Among the clusters present in this set of species we found andrastin A and its related cluster atlantinone A, mycophenolic acid, patulin, penitrem A and the cluster responsible for the synthesis of roquefortine C/glandicoline A/glandicoline B/meleagrin. We confirmed the presence of these clusters in several of the Penicillium species conforming our dataset and verified their capacity to synthesize them in a chestnut-based medium with chemical analysis. Interestingly, we identified mycotoxin clusters in some species for the first time, such as the andrastin A cluster in P. flavigenum and P. taurinense, and the roquefortine C cluster in P. nalgiovense and P. taurinense. Chestnuts proved to be an optimal substrate for species of Penicillium with different mycotoxigenic potential, opening the door to risks related to the occurrence of multiple mycotoxins in the same food matrix.

Evaluation of the safety and quality of Brazil nuts (Bertholletia excelsa) using the tools of dna sequencing technology and aflatoxin profile

Introduction

Brazil nuts (BNs) result from sustainable extraction and are widely exploited in the Amazon region. Due to the production characteristics in the forest and the nutritional characteristics of these nuts, the occurrence of fungal contamination and the presence of aflatoxins are extensively discussed in the literature as a great aspect of interest and concern. This study aims to evaluate the microbial profile through DNA sequencing and amplification of 16S and ITS genes for bacterial and fungal analysis, respectively, and the presence of mycotoxins using high-performance liquid chromatography with fluorescence detection (HPLC-FD) from different fractions of the nuts processed.

Methods

The BN samples, harvest A (HA) and harvest B (HB), from two different harvests were collected in an extractive cooperative in the Amazon region for microbiological analysis (from DNA extraction and amplification of 16S genes, bacteria analysis, and ITS for fungi) and mycotoxins (aflatoxins AFB1, AFB2, AFG1, and AFG2) using HPLC-FD/KobraCell®.

Results and discussion

The samples showed a very different microbiome and aflatoxin profile. Genera such as Rothia (HA) and Cronobacter (HB) were abundant during the analysis of bacteria; as for fungi, the genera Aspergillus, Fusarium, Penicillium, and Alternaria were also considered prevalent in these samples. Soil microorganisms, including those pathogenic and related to inadequate hygienic-sanitary production practices, as well as aflatoxins, were found in the samples. However, they were within the established limits permitted by Brazilian legislation. Nuts have a diverse microbiota and are not restricted to fungi of the genus Aspergillus. The microbiological and toxicological profile can vary significantly within the same nut in the same extraction region and can be exacerbated by global climate changes. Therefore, it is necessary to advance sanitary educational actions by applying good production practices and inspection programs to ensure the sustainability and quality of the BN production chain.

Effect of different storage conditions on the stability and safety of almonds

Almond production in Portugal is of great importance for the economy of their main producing areas. However, the contamination of these nut fruits with fungi and mycotoxins poses a significant risk to food safety and security. This work intended to evaluate the influence of storage conditions on the microbial and mycotoxin stability and safety of almonds throughout long-term storage. Two almond varieties-Lauranne and Guara-were submitted to three different storage conditions, namely, 4°C with noncontrolled relative humidity (RH), 60% RH at 25°C, and 70% RH at 25°C, for a storage period of 9 months. Samples were collected after 0, 3, 6, and 9 months of storage and analyzed for microbial loads (aerobic mesophiles, yeasts, and molds), mold incidence and diversity, and mycotoxin contamination. In total, 26 species were identified belonging to 6 genera: Aspergillus, Cladosporium, Fusarium, Penicillium, Paecilomyces, and Talaromyces. For the variety Guara, mycotoxins related to Aspergillus sect. Flavi, such as aflatoxins, averufin, versicolorin C, and norsolorinic acid, were detected only after 9 months of storage at 70% and 60% RH. Penicillium mycotoxins, such as quinolactacin A and roquefortine C, were also detected. For the variety Lauranne, Penicillium mycotoxins were detected, such as citrinin, quinolactacins A and B, roquefortines C and D, cyclopenin, cyclopenol, penitrem A, viridicatin, and viridicatol. Mycotoxins related to Aspergillus, such as aspulvinone E, flavoglaucin, paspalin, asperglaucide, asperphenamate, cyclo(L-Pro-L-Tyr), and cyclo(L-Pro-L-Val), were also detected. PRACTICAL APPLICATION: (Optional, for JFS Research Articles ONLY) The quality of almonds depends on the storage period and the RH and temperature at which they are stored. Storage of almonds at 60% RH at 25°C is a good storage condition to maintain the stability and safety of nuts in terms of microbial and mycotoxin contaminations.

Fungi Occurrence in Ready-to-Eat Hazelnuts (Corylus avellana) From Different Boreal Hemisphere Areas

The present study evaluated the fungal contamination of ready-to-eat dried hazelnuts considering for the first time the application of the same condition drying process of several hazelnut cultivars from different boreal hemisphere areas. Fifty lots of hazelnuts (Corylus avellana), belonging to eight cultivars from seven regions in four countries, were analyzed for fungal microbiota, describing both load levels and species diversity. For this purpose, a polyphasic approach consisting of morphological examination (optical and scanning electron microscope observation) and molecular characterization [PCR-DGGE analysis and sequence analyses of the internal transcribed spacer (ITS)] was performed. The results show that different fungal populations occur in dried hazelnuts regardless of their geographical area of production. Although some varieties appear to be relatively less susceptible, species related to Aspergillus, such as A. commune and A. ochraceus, Penicillium, including P. commune, P. solitum, and P. expansum, and Rhizopus, for instance, R. stolonifer and R. oryzae, have generally been found. A related character “hazelnut cultivar—fungi” was found for species related to the genera Trichoderma and Fusarium, including F. oxyxporum, F. solani, and F. falciforme. All 14 species found are known to host pathogenic strains. Therefore, their presence in a ready-to-eat product, such as dried hazelnuts, can pose a real danger to the consumer. Based on these considerations, the development of new protective strategies seems highly desirable. The species-level description of the contaminating fungal community acquired through this study is the starting point for the development of tailor-made protective biotechnologies.

[Adulteration identification of wheat flour in chestnut flour based on differences in mycotoxin contamination by liquid chromatography-tandem mass spectrometry]

An analytical method based on dispersive solid-phase extraction (d-SPE) and ultrafast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) was employed for the determination of 43 mycotoxins in chestnut flour and wheat flour. A total of 128 samples consisting of 48 chestnut samples and 80 wheat flour samples were collected randomly and subjected to analysis. Finally, five specific toxins were selected as markers to identify these two foodstuffs. Acetonitrile-water (84∶16, v/v) was used to extract mycotoxins from chestnut flour and wheat flour. After extraction, the supernatant was transferred to the d-SPE equipment, using which purification was performed with C18 and EMR-Lipid (lipid adsorbent). Chromatographic separation was carried out by gradient elution with eluent A (ESI+: 0.1% formic acid, ESI-: water) and eluent B (ESI+: methanol-acetonitrile (1∶1) containing 0.1% formic acid, ESI-: acetonitrile) on a BEH C18 column (100 mm×2.1 mm, 1.7 μm). Quantitative analysis was performed with the aid of matrix-matched curves. When establishing the method, the experimental matrix for optimization was designed by central-composite design based on the response surface methodology. Quadratic polynomial equations were deduced to describe the relationships between the responses and variables, and assess the interaction effects among the variables to acquire the true optimal conditions with less workload. Using the optimum experimental conditions, the accuracy of the proposed method was determined through three-level spiking tests, while the precision was evaluated in terms of the repeatability (six replications per level). Satisfactory precisions (RSDs≤7.5% in chestnut flour and RSDs≤9.3% in wheat flour) were achieved in all tested assays. The recoveries were also acceptable, and ranged from 72.4% to 109.4% for chestnut flour and from 70.7% to 112.9% for wheat flour. The matrix effects of mycotoxins were 48%-128% in wheat flour and 41%-112% in chestnut flour. The detectability of mycotoxins in the two matrices was assessed by spiking the blank extracts with various low concentrations, and determined as the lowest values that can produce chromatographic peaks at a signal-to-noise ratio (S/N) of 3∶1. The obtained limits of quantification varied from 0.10 μg/kg to 20 μg/kg (bongkrekic acid) in both investigated matrices. Satisfactory linearities were obtained, with correlation coefficients>0.9991 for all the analytes. After validation, the contamination status of the multiple mycotoxins was evaluated for various concentration ranges. Based on the obtained data, both wheat flour and chestnut flour were severely contaminated, with 17 mycotoxins detected in them. Particularly, chaetoglobosin A, ochratoxin B, and penicillic acid were only detected in chestnut flour, while 3-acetyl-deoxynivalenol, deoxynivalenol, and nivalenol were detected in wheat flour. Further, the positive rates and contamination concentrations of chaetoglobosin A, ochratoxin B, and penicillic acid were not significant; hence, they did not qualify as identification markers. On the other hand, the incidence of deoxynivalenol in wheat flour almost reached 100%, which is very significant. Finally, deoxynivalenol and its four derivatives (3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, deepoxy-deoxynivalenol, and nivalenol) were treated as adulteration markers for the two foodstuffs. To improve the reliability of the conclusion, all samples were re-tested using the first method prescribed by the National Food Safety Standard, i. e., GB 5009.111-2016. Ten chestnut flour samples were also randomly selected to prepare moldy samples under suitable environmental conditions for the growth of Fusarium, to verify the production and release of deoxynivalenol and its derivative mycotoxins under the extreme conditions. The distribution data for these mycotoxins were consistent with those obtained by d-SPE, confirming that the adulteration criterion is trustworthy. The established method is simple, rapid, sensitive, and accurate, and can effectively meet the requirements for the simultaneous determination of multiple mycotoxins in chestnut flour and wheat flour. Moreover, the adulteration results, which were obtained for natural contaminants (deoxynivalenol and its four derivatives), are less affected by humans and hence, much more accurate and reliable.

Influence of Climate Change on Metabolism and Biological Characteristics in Perennial Woody Fruit Crops in the Mediterranean Environment

The changes in the state of the climate have a high impact on perennial fruit crops thus threatening food availability. Indeed, climatic factors affect several plant aspects, such as phenological stages, physiological processes, disease-pest frequency, yield, and qualitative composition of the plant tissues and derived products. To mitigate the effects of climatic parameters variability, plants implement several strategies of defense, by changing phenological trends, altering physiology, increasing carbon sequestration, and metabolites synthesis. This review was divided into two sections. The first provides data on climate change in the last years and a general consideration on their impact, mitigation, and resilience in the production of food crops. The second section reviews the consequences of climate change on the industry of two woody fruit crops models (evergreen and deciduous trees). The research focused on, citrus, olive, and loquat as evergreen trees examples; while grape, apple, pear, cherry, apricot, almond, peach, kiwi, fig, and persimmon as deciduous species. Perennial fruit crops originated by a complex of decisions valuable in a long period and involving economic and technical problems that farmers may quickly change in the case of annual crops. However, the low flexibility of woody crops is balanced by resilience in the long-life cycle.

Mycotoxins Analysis in Cereals and Related Foodstuffs by Liquid Chromatography-Tandem Mass Spectrometry Techniques

In the entire world, cereals and related foodstuffs are used as an important source of energy, minerals, and vitamins. Nevertheless, their contamination with mycotoxins kept special attention due to harmful effects on human health. The present paper was conducted to evaluate published studies regarding the identification and characterization of mycotoxins in cereals and related foodstuffs by liquid chromatography coupled to (tandem) mass spectrometry (LC-MS/MS) techniques. For sample preparation, published studies based on the development of extraction and clean-up strategies including solid-phase extraction, solid-liquid extraction, and immunoaffinity columns, as well as on methods based on minimum clean-up (quick, easy, cheap, effective, rugged, and safe (QuEChERS)) technology, are examined. LC-MS/MS has become the golden method for the simultaneous multimycotoxin analysis, with different sample preparation approaches, due to the range of different physicochemical properties of these toxic products. Therefore, this new strategy can be an alternative for fast, simple, and accurate determination of multiclass mycotoxins in complex cereal samples.

Effect of Drying Temperatures and Exposure Times on Aspergillus flavus Growth and Aflatoxin Production on Artificially Inoculated Hazelnuts

ABSTRACT

Aspergillus flavus may colonize hazelnuts and produce aflatoxins in the field and during storage. The main purpose of this study was to investigate the influence of drying temperature and exposure times on the viability of A. flavus and its ability to produce aflatoxins during the drying process and storage. Hazelnuts were inoculated with A. flavus and dried at different temperatures to reach 6% moisture content and a water activity (aw) of 0.71, a commercial requirement to avoid fungal development and aflatoxin contamination. Hazelnuts were dried at 30, 35, 40, 45, and 50°C and subsequently stored at 25°C for 14 days. After drying at 30, 35, and 40°C, increased amounts of A. flavus were evident, with the highest concentration occurring after drying at 35°C ([6.1 ± 2.4] × 106A. flavus CFU/g). At these temperatures, aflatoxins were detected only at 30 and 35°C. Aflatoxins, however, were present at higher levels after drying at 30°C, with concentrations of 1.93 ± 0.77 μg/g for aflatoxin B1 (AFB1) and 0.11 ± 0.04 μg/g for aflatoxin B2 (AFB2). After 14 days of storage, the highest A. flavus concentration and the highest levels of mycotoxins were detected in samples treated at 35°C ([8.2 ± 2.1] × 107A. flavus CFU/g and 9.30 ± 1.58 μg/g and 0.89 ± 0.08 μg/g for AFB1 and AFB2, respectively). In hazelnuts dried at 45 or 50°C, no aflatoxins were found either after drying or storage, and a reduction of A. flavus viable conidia was observed, suggesting that a shorter and warmer drying is essential to guarantee nut safety. The lowest temperature that guarantees the lack of aflatoxins should be selected to maintain the organoleptic quality of hazelnuts. Therefore, 45°C should be the recommended drying temperature to limit A. flavus growth and aflatoxin contamination on hazelnuts.

HIGHLIGHTS

Food hazards on the European Union market: The data analysis of the Rapid Alert System for Food and Feed

The aim of the study was to examine similarities in notifications on main hazards within food reported in the Rapid Alert System for Food and Feed (RASFF) in 1979-2017. The main problems were mycotoxins in nuts, pathogenic microorganisms in poultry meat and fish, pesticide residues in fruits and vegetables, and heavy metals in fish. The increase in the number of notifications has been observed since 2002/2003. Products were notified mainly by Italy, Germany, and United Kingdom and originated from Asian and European Union countries. The notification basis was border control and official control, and the notification type was border rejections, information, and alerts. Notified products were not distributed and not placed on the market, distribution status could be also not specified, or distribution was possible, also to other countries. The risk decision on hazard was usually not made. Products were redispatched, withdrawn from the market, and destroyed, or import was not authorized. Remarks, which can be used to improve the RASFF database, were also presented. It was further pointed out that European law should significantly reduce the use of pesticides, drugs, and food additives, and European agriculture should be reoriented from an intensive farming to a more sustainable and ecological one.

Advances in Occurrence, Importance, and Mycotoxin Control Strategies: Prevention and Detoxification in Foods

Mycotoxins are toxic substances that can infect many foods with carcinogenic, genotoxic, teratogenic, nephrotoxic, and hepatotoxic effects. Mycotoxin contamination of foodstuffs causes diseases worldwide. The major classes of mycotoxins that are of the greatest agroeconomic importance are aflatoxins, ochratoxins, fumonisins, trichothecenes, emerging Fusarium mycotoxins, enniatins, ergot alkaloids, Alternaria toxins, and patulin. Thus, in order to mitigate mycotoxin contamination of foods, many control approaches are used. Prevention, detoxification, and decontamination of mycotoxins can contribute in this purpose in the pre-harvest and post-harvest stages. Therefore, the purpose of the review is to elaborate on the recent advances regarding the occurrence of main mycotoxins in many types of important agricultural products, as well as the methods of inactivation and detoxification of foods from mycotoxins in order to reduce or fully eliminate them.

Aflatoxins and ochratoxin A in chocolate products in Turkey

This survey describes the occurrence and levels of AFs and OTA in chocolate products consumed in Turkey. A total of 130 samples, including bitter chocolate, milk chocolate and chocolate wafers were analysed for these mycotoxins by high-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD). The values of recovery (81-92%) and precision (RSD < 9%) fulfilled the requirements of EC Regulation No. 401/2006. OTA was the most prevalent mycotoxin, with an incidence of 46.7% in bitter chocolate, 22.8% in milk chocolate and 17.4% in chocolate wafers, ranging from 0.18 to 0.75 μg kg^-1. AFs were detected in 13.3% of bitter chocolate, in 19.6% of milk chocolate and in 8.7% of chocolate wafers, in concentrations ranging from 0.15 to 2.04 μg kg^-1.

Thin Films Sensor Devices for Mycotoxins Detection in Foods: Applications and Challenges

Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of mycotoxins include gas chromatography and high-performance liquid chromatography coupled with mass spectrometry or other detectors (fluorescence or UV detection), thin layer chromatography and enzyme-linked immunosorbent assay. These techniques are generally straightforward and yield reliable results; however, they are time-consuming, require extensive preparation steps, use large-scale instruments, and consume large amounts of hazardous chemical reagents. Rapid detection of mycotoxins is becoming an increasingly important challenge for the food industry in order to effectively enforce regulations and ensure the safety of food and feed. In this sense, several studies have been done with the aim of developing strategies to detect mycotoxins using sensing devices that have high sensitivity and specificity, fast analysis, low cost and portability. The latter include the use of microarray chips, multiplex lateral flow, Surface Plasmon Resonance, Surface Enhanced Raman Scattering and biosensors using nanoparticles. In this perspective, thin film sensors have recently emerged as a good candidate technique to meet such requirements. This review summarizes the application and challenges of thin film sensor devices for detection of mycotoxins in food matrices.

Chestnut Drying Is Critical in Determining Aspergillus flavus Growth and Aflatoxin Contamination

Chestnut drying is used to prevent postharvest losses and microorganism contamination during storage. Several studies reported the contamination by aflatoxins (AFs) produced by Aspergillus spp. in chestnuts. The effect of drying temperatures (from 30 to 50 °C) was evaluated on the growth of A. flavus and the production of aflatoxins in chestnuts. The influence of the treatment on the proximate composition, the total phenol content and antioxidant activity of chestnuts was considered. Fungal colonization was observed on the nuts dried at 30, 35, and 40 °C; the incidence was lower at 40 °C. The highest concentrations of AFB₁ and AFB₂ were produced at 40 °C. No aflatoxins were detected at 45 or 50 °C. At 40 °C A. flavus was under suboptimal conditions for growth (a_w 0.78), but the fungus was able to synthesize aflatoxins. As the temperatures applied increased, the total phenol content increased, while the antioxidant activity decreased. A drying treatment at 45 °C for seven days (a_w 0.64) could be a promising method to effectively control both the growth of aflatoxigenic fungi and the production of aflatoxins. This study provides preliminary data useful to improve the current drying conditions used in chestnut mills, to reduce both fungal growth and aflatoxin production.

Mycotoxin Contamination of Beverages Obtained from Tropical Crops

This review is mainly centered on beverages obtained from tropical crops, including tea, nut milk, coffee, cocoa, and those prepared from fruits. After considering the epidemiological data found on the matrices above, the focus was given to recent methodological approaches to assess the most relevant mycotoxins. Aspects such as singularities among the mycotoxin and the beverage in which their were found, and the economic effects and repercussions that the mycotoxin-tainted ingredients have on the beverage industry were pointed out. Finally, the burden of their consumption through beverages, including risk and health effects on humans, was addressed as well.

Several species of Penicillium isolated from chestnut flour processing are pathogenic on fresh chestnuts and produce mycotoxins

A collection of 124 isolates of Penicillium spp. was created by monitoring fresh chestnuts, dried chestnuts, chestnut granulates, chestnut flour and indoor chestnut mills. Sequencing of the ITS region, β-tubulin and calmodulin, macro-morphology and secondary metabolite production made it possible to determine 20 species of Penicillium. P. bialowiezense was dominant in the fresh chestnuts, while P. crustosum was more frequent in the other sources. A pathogenicity test on chestnut showed that around 70% of the isolates were virulent. P. corylophilum and P. yezoense were not pathogenic, while the other 18 species had at least one virulent isolate. P. expansum and P. crustosum were the most virulent. The isolates were characterized to establish their ability to produce 14 toxic metabolites in vivo: 59% were able to produce at least one mycotoxin. P. expansum was able to produce patulin, chaetoglobosin A and roquefortine, while P. bialowiezense produced C. Mycophenolic acid. Cyclopenins and viridicatins were produced by most of the P. crustosum, P. polonicum, P. solitum and P. discolour isolates. Some of the P. crustosum isolates were also able to produce roquefortine C or penitrem A. Information about the occurrence of Penicillium spp. and their mycotoxins will help producers to set up management procedures that can help to control the fungal growth and the mycotoxin production of chestnuts.

Isolation and Evaluation of New Antagonist Bacillus Strains for the Control of Pathogenic and Mycotoxigenic Fungi of Fig Orchards

Bacillus is an antagonistic bacteria that shows high effectiveness against different phytopathogenic fungi and produces various lytic enzymes, such as chitosanase, chitinase, protease, and gluconase. The aim of this study is to determine Bacillus spp. for lytic enzyme production and to evaluate the antifungal effects of the selected strains for biocontrol of mycotoxigenic and phytopathogenic fungi. A total of 92 endospore-forming bacterial isolates from the 24 fig orchard soil samples were screened for chitosanase production, and six best chitosanolytic isolates were selected to determine chitinase, protease, and N-acetyl-β-hexosaminidase activity and molecularly identified. The antagonistic activities of six Bacillus strains against Aspergillus niger EGE-K-213, Aspergillus foetidus EGE-K-211, Aspergillus ochraceus EGE-K-217, and Fusarium solani KCTC 6328 were evaluated. Fungal spore germination inhibition and biomass inhibition activities were also measured against A. niger EGE-K-213. The results demonstrated that Bacillus mojavensis EGE-B-5.2i and Bacillus thuringiensis EGE-B-14.1i were more efficient antifungal agents against A. niger EGE-K-213. B. mojavensis EGE-B-5.2i has shown maximum inhibition of the biomass (30.4%), and B. thuringiensis EGE-B-14.1i has shown maximum inhibition of spore germination (33.1%) at 12 h. This is the first study reporting the potential of antagonist Bacillus strains as biocontrol agents against mycotoxigenic fungi of fig orchads.

Assessment of azole fungicides as a tool to control growth of Aspergillus flavus and aflatoxin B1 and B2 production in maize

Aspergillus flavus is a highly aflatoxin (AF)-producing species infecting maize and other crops. It is dominant in tropical regions, but it is also considered an emerging problem associated with climate change in Europe. The aim of this study was to assess the efficacy of azole fungicides (prochloraz, tebuconazole and a 2:1 (w/w) mixture of prochloraz plus tebuconazole) to control the growth of A. flavus and AF production in yeast-extract-sucrose (YES) agar and in maize kernels under different water activities (a_w) and temperatures. Aflatoxins B₁ and B₂ were determined by LC with fluorescence detection and post-column derivatisation of AFB₁. In YES medium and maize grains inoculated with conidia of A. flavus, the growth rate (GR) of the fungus and AFB₁ and AFB₂ production were significantly influenced by temperature and treatment. In YES medium and maize kernels, optimal temperatures for GR and AF production were 37 and 25°C, respectively. In maize kernels, spore germination was not detected at the combination 37ºC/0.95 a_w; however, under these conditions germination was found in YES medium. All fungicides were more effective at 0.99 than 0.95 a_w, and at 37 than 25ºC. Fungicides effectiveness was prochloraz > prochloraz plus tebuconazole (2:1) > tebuconazole. AFs were not detected in cultures containing the highest fungicide doses, and only very low AF levels were found in cultures containing 0.1 mg l^-1 prochloraz or 5.0 mg l^-1 tebuconazole. Azoles proved to be highly efficient in reducing A. flavus growth and AF production, although stimulation of AF production was found under particular conditions and low-dosage treatments. Maize kernels were a more favourable substrate for AF biosynthesis than YES medium. This paper is the first comparative study on the effects of different azole formulations against A. flavus and AF production in a semi-synthetic medium and in maize grain under different environmental conditions.

Is Gamma Radiation Suitable to Preserve Phenolic Compounds and to Decontaminate Mycotoxins in Aromatic Plants? A Case-Study with Aloysia citrodora Paláu

This study aimed to determine the effect of gamma radiation on the preservation of phenolic compounds and on decontamination of dry herbs in terms of ochratoxin A (OTA) and aflatoxin B1 (AFB1), using Aloysia citrodora Paláu as a case study. For this purpose, artificially contaminated dry leaves were submitted to gamma radiation at different doses (1, 5, and 10 kGy; at dose rate of 1.7 kGy/h). Phenolic compounds were analysed by HPLC-DAD-ESI/MS and mycotoxin levels were determined by HPLC-fluorescence. Eleven phenolic compounds were identified in the samples and despite the apparent degradation of some compounds (namely verbasoside), 1 and 10 kGy doses point to a preservation of the majority of the compounds. The mean mycotoxin reduction varied between 5.3% and 9.6% for OTA and from 4.9% to 5.2% for AFB1. It was not observed a significant effect of the irradiation treatments on mycotoxin levels, and a slight degradation of the phenolic compounds in the irradiated samples was observed.

Inhibitory effect of essential oils on growth and on aflatoxins production by Aspergillus parasiticus

The aim of this work was to assess the inhibitory effect of essential oils on the growth and aflatoxin production of Aspergillus parasiticus, as well as to correlate it with the chemical composition of the essential oils. Essential oils from six aromatic species (Cymbopogon citratus, Eucalyptus globulus, Origanum vulgare, Ruta graveolens, Salvia officinalis, Satureja montana) were characterised by gas chromatography and tested for their inhibitory effect against A. parasiticus strain MUM 92.02. Furthermore, the in vitro inhibitory effects of these essential oils on the production of aflatoxins were evaluated by HPLC. Results showed that all essential oils retarded the time for visible growth. Growth rate was affected differently depending on the essential oil. S. montana essential oil prevented growth in all cases. The essential oil of R. graveolens inhibited most of the aflatoxin production even though growth inhibition was low, while with C. citratus essential oil trace levels of aflatoxins were detected. Essential oils containing carvacrol and/or thymol (S. montana and O. vulgare) have the highest activity against fungal growth, while an essential oil (R. graveolens) containing 2-undecanone and 8-phenyl-2-octanone inhibited the synthesis of aflatoxins. Although the main component of this essential oil was 2-undecanone (91%), when pure 2-undecanone was tested, it did not inhibit aflatoxin production. Inhibition activity is probably due to the recently identified minor compound or to a synergistic effect. Essential oils seem to be a good alternative to fungicides not only because of environmental issues but also because they do not seem to enhance mycotoxin production as it has been reported for some fungicides.

Biodiversity of mycobiota throughout the Brazil nut supply chain: From rainforest to consumer

A total of 172 Brazil nut samples (114 in shell and 58 shelled) from the Amazon rainforest region and São Paulo state, Brazil was collected at different stages of the Brazil nut production chain: rainforest, street markets, processing plants and supermarkets. The mycobiota of the Brazil nut samples were evaluated and also compared in relation to water activity. A huge diversity of Aspergillus and Penicillium species were found, besides Eurotium spp., Zygomycetes and dematiaceous fungi. A polyphasic approach using morphological and physiological characteristics, as well as molecular and extrolite profiles, were studied to distinguish species among the more important toxigenic ones in Aspergillus section Flavi and A. section Nigri. Several metabolites and toxins were found in these two sections. Ochratoxin A (OTA) was found in 3% of A. niger and 100% of A. carbonarius. Production of aflatoxins B and G were found in all isolates of A. arachidicola, A. bombycis, A. nomius, A. pseudocaelatus and A. pseudonomius, while aflatoxin B was found in 38% of A. flavus and all isolates of A. pseudotamarii. Cyclopiazonic acid (CPA) was found in A. bertholletius (94%), A. tamarii (100%), A. caelatus (54%) and A. flavus (41%). Tenuazonic acid, a toxin commonly found in Alternaria species was produced by A. bertholletius (47%), A. caelatus (77%), A. nomius (55%), A. pseudonomius (75%), A. arachidicola (50%) and A. bombycis (100%). This work shows the changes of Brazil nut mycobiota and the potential of mycotoxin production from rainforest to consumer, considering the different environments which exist until the nuts are consumed.

Mycobiota and Mycotoxins in Traditional Medicinal Seeds from China

The multi-mycotoxin occurrence for internal and superficial fungi contamination were comprehensively assessed in medicinal seeds used as food or beverage. Based on a polyphasic approach using morphological characters, β-tubulin and ITS gene blast, a total of 27 species belonging to 12 genera were identified from surface-sterilized seeds. Chaetomium globosporum was most predominant (23%), followed by Microascus trigonosporus (12%) and Alternaria alternata (9%). With respect to superficial mycobiota, thirty-four species belonging to 17 genera were detected. Aspergillus niger and Penicillium polonicum were predominant (12% and 15%, respectively). Medicinal seed samples and potential toxigenic fungi were tested for ochratoxin A (OTA) and aflatoxins (AFB1, AFB2, AFG1, AFG2) using UPLC-MS/MS. Platycladi seeds were contaminated with AFB1 (52.0 µg/kg) and tangerine seed was contaminated with OTA (92.3 µg/kg). Subsequent analysis indicated that one A. flavus strain isolated from platycladi seed was able to synthesize AFB1 (102.0 µg/kg) and AFB2 (15.3 µg/kg). Two P. polonicum strains isolated from tangerine and lychee seeds were able to synthesize OTA (4.1 µg/kg and 14.8 µg/kg, respectively). These results identify potential sources of OTA and aflatoxins in medicinal seeds and allude to the need to establish permitted limits for these mycotoxins in these seeds that are commonly consumed by humans.

Impact of postharvest processing on the fungal population contaminating African walnut shells (Tetracarpidium conophorum Mull. Arg) at different maturity stages and potential mycotoxigenic implications

African walnut (Tetracarpidium conophorum Mull. Arg) is commonly processed by boiling or toasting and consumed as a snack or used as a thickener in many West African soup preparations. The nuts are usually exposed to both high temperatures and high relative humidity in open markets which predisposes them to fungal growth. Hence, the dangers of spore inhalation and resultant mycosis cannot be over-emphasized as retailers and consumers are always in direct contact with these nuts during harvest, processing and consumption. So far, there is no reported research on potential mycotoxin contamination of African walnut and whether this risk might be accentuated by processing. African walnut, at early and late maturity stages, were processed by toasting, boiling or left unprocessed before being stored at 25°C and 37°C, respectively under controlled relative humidity for 7days. Nuts were cracked and shell pieces cultured in malt extract agar (MEA) and Dichloran Glycerol 18 (DG18) media and incubated at 25°C for 7days. Results revealed that potential mycotoxigenic species - Aspergillus section Nigri, Aspergillus flavus/parasiticus, Fusarium spp. and Penicillium spp. - were frequently isolated. When compared with unprocessed nuts, toasting completely prevented fungal contamination in shell pieces from nuts in the non-stored (NSN) group at the early maturity stage, while boiling significantly reduced the level of contamination to about 58% (p<0.05). In general, simulating open market conditions caused 100% fungal contamination in all boiled samples and toasted samples at early maturity. However, contamination in toasted samples at late maturity was increased to 90 and 70% at 25°C in DG18 and MEA, respectively, while at 37°C contamination was 40 and 60% in DG18 and MEA, respectively. Mycotoxin analysis using Yeast Extract Sucrose (YES) agar and High Performance Liquid Chromatography (HPLC)-Fluorescence detection (FLD) showed that Aflatoxins - G1 (AFG1), B1 (AFB1), G2 (AFG2), and B2 (AFB2) were produced by 20 isolates with both AFG1 and AFB1 being predominant at concentration ranges 4.33-32,200 and 4.20-22,700ng/g plug weight, respectively. No ochratoxin A (OTA) was detected out of 23 isolates analysed. From these findings, it is suggested that toasting of nuts, preferably at early maturity is a safer processing option than boiling in terms of prevention of possible fungal growth on nut shells and risk of mycotoxin contamination.

Effect of almond processing on levels and distribution of aflatoxins in finished products and byproducts

The fate of aflatoxins during processing of contaminated almonds into nougat, pastries, and almond syrup was evaluated by testing the effect of each processing step (blanching, peeling, roasting, caramelization, cooking, and water infusion) on the distribution and levels of aflatoxins. Blanching and peeling did not reduce total aflatoxins that were distributed between peeled almonds (90-93%) and skins (7-10%). Roasting of peeled almonds reduced up to 50% of aflatoxins. Up to 70% reduction of aflatoxins was observed during preparation and cooking of almond nougat in caramelized sugar. Aflatoxins were substantially stable during preparation and cooking of almond pastries. The whole process of almond syrup preparation produced a marked increase of total aflatoxins (up to 270%) that were distributed between syrup (18-25%) and spent almonds (75-82%). The increase of total aflatoxins was probably due to the activation of almond enzymes during the infusion step that released free aflatoxins from masked aflatoxins.

Monitoring and determination of fungi and mycotoxins in stored Brazil nuts

Brazil nut (Bertholletia excelsa) is an important commodity from the Brazilian Amazon, and approximately 37,000 tons (3.36 × 10⁷ kg) of Brazil nuts are harvested each year. However, substantial nut contamination by Aspergillus section Flavi occurs, with subsequent production of mycotoxins. In this context, the objective of the present investigation was to evaluate the presence of fungi and mycotoxins (aflatoxins and cyclopiazonic acid) in 110 stored samples of cultivated Brazil nut (55 samples of nuts and 55 samples of shells) collected monthly for 11 months in Itacoatiara, State of Amazonas, Brazil. The samples were inoculated in duplicate onto Aspergillus flavus and Aspergillus parasiticus agar and potato dextrose agar for the detection of fungi, and the presence of mycotoxins was determined by high-performance liquid chromatography. The most prevalent fungi in nuts and shells were Aspergillus spp., Fusarium spp., and Penicillium spp. A polyphasic approach was used for identification of Aspergillus species. Aflatoxins and cyclopiazonic acid were not detected in any of the samples analyzed. The low water activity of the substrate was a determinant factor for the presence of fungi and the absence of aflatoxin in Brazil nut samples. The high frequency of isolation of aflatoxigenic Aspergillus section Flavi strains, mainly A. flavus, and their persistence during storage increase the chances of aflatoxin production on these substrates and indicates the need for good management practices to prevent mycotoxin contamination in Brazil nuts.

Aflatoxins in various food from Istanbul, Turkey

The present work reports the total aflatoxin and aflatoxin B1 levels in 62 food samples from Istanbul, Turkey. The total aflatoxin content in dried American cucumber, squash, tomato, okra and saffron samples was found to be 1.7 μg/kg. AFB1 levels in five dried vegetables (red bell pepper, American cucumber, squash, tomato and okra), two tea (linden and jasmine flower) and three spice samples (cardamom, galangal and saffron) were 1 μg/kg. Of the tested samples, 76% exceeded legal limits of total aflatoxin. The highest levels were determined in chestnut (232.9 μg/kg), nutmeg (206.1 μg/kg) and sumac (182.5 μg/kg). These findings confirm the existing knowledge that food should be regularly and effectively controlled.

Development and validation of a (semi-)quantitative UHPLC-MS/MS method for the determination of 191 mycotoxins and other fungal metabolites in almonds, hazelnuts, peanuts and pistachios

A multi-target method for the determination of 191 fungal metabolites in almonds, hazelnuts, peanuts and pistachios was developed. The method includes all mycotoxins regulated in the European Union and mycotoxins regularly found in food. After extraction with an acidified acetonitrile water mixture, the raw extract was diluted and injected directly into the UHPLC-MS/MS system. In two chromatographic runs, analysis was performed in positive and in negative ionisation mode. The method was in-house validated for the most important 65 analytes in these four commodities. Apparent recoveries between 80 and 120 % were obtained for about half of the analyte–matrix combinations. Good repeatabilities (standard deviations < 10 %) were achieved for the vast majority (83 %) of all cases. Only in 6 % of all combinations did the standard deviations exceed 15 %. Matrix effects, arising during electrospray ionisation, significantly influenced the determination. For instance, signal suppression was observed for several early-eluting analytes and also signal enhancement up to 295 % for physcion in peanuts was determined. Concerning extraction recovery, 94 % of the analyte–matrix combinations showed values higher than 50 %. Lower limits of quantification ranged between 0.04 μg kg⁻¹ for enniatin B3 in peanuts and 500 μg kg⁻¹ for HC toxin in hazelnuts. Additionally, the applicability of the developed method was demonstrated through the analysis of 53 naturally contaminated nut samples from Austria and Turkey. Overall, 40 toxins were quantified; the most frequently found mycotoxins were beauvericin (79 %), enniatin B (62 %) and macrosporin (57 %). In the most contaminated hazelnut sample, 26 different fungal metabolites were detected.