Multiple mycotoxin analysis in nut products: Occurrence and risk characterization.
Nuts consumption plays an important role in Mediterranean diet, being a good source of proteins, vitamins, minerals and unsaturated fatty acids. However, nuts can be also a source of harmful mycotoxins with negative impact on human health. In this work, the occurrence of 16 mycotoxins belonging to different chemical classes, was assessed in several nut products. The analytical method used was based on modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. An extensive evaluation of different sorbents used in dispersive SPE (d-SPE) cleanup step of QuEChERS was performed. Detection limits achieved were less than 3.5 μg/kg for all the compounds and the average recoveries varied from 70 to 93%, with relative standard deviations (RSD) ≤13%. Eleven out of sixteen mycotoxins under study were found in the 37 nut samples analysed. Overall, deoxynivalenol (DON), aflatoxin-G2 (AFG2), fusarenon-X (FUS X) and fumonisin-B1 (FB1) were the compounds more commonly detected. The higher contamination value was observed in a cashew sample containing 336.5 μg/kg of DON. The combination of occurrence and consumption data allowed to assess the exposure and characterize the associated risk of nut products consumption by the Portuguese population.
Peanuts, Aflatoxins and Undernutrition in Children in Sub-Saharan Africa.
Peanuts (Arachis hypogaea) is an important and affordable source of protein in most of Sub-Saharan Africa (SSA) and a popular commodity and raw material for peanut butter, paste and cooking oil. It is a popular ingredient for foods used at the point of weaning infants from mother's milk. It is at this critical point that childhood undernutrition occurs and the condition manifests as stunting, wasting and growth restriction and accounts for nearly half of all deaths in children under five years of age in SSA. Undernutrition is multi-factorial but weaning foods contaminated with microbiological agents (bacteria and fungi) and natural toxins have been shown to play a big part. While peanuts may provide good nutrition, they are also highly prone to contamination with mycotoxigenic fungi. The high nutritive value of peanuts makes them a perfect substrate for fungal growth and potential aflatoxin contamination. Aflatoxins are highly carcinogenic and mutagenic mycotoxins. This article reviews the nutritional value and aflatoxin contamination of peanuts, the role they play in the development of childhood malnutrition (including the different theories of aetiology) and immunological problems in children. We also discuss the control strategies that have been explored and advocacy work currently taking shape in Africa to create more awareness of aflatoxins and thus combat their occurrence with the goal of reducing exposure and enhancing trade and food safety.
Suppression of aflatoxin production in Aspergillus species by selected peanut (Arachis hypogaea) stilbenoids.
Aspergillus flavus is a soil fungus that commonly invades peanut seeds and often produces the carcinogenic aflatoxins. Under favorable conditions, the fungus-challenged peanut plant produces and accumulates resveratrol and its prenylated derivatives in response to such invasion. These prenylated stilbenoids are considered peanut antifungal phytoalexins. However, the mechanism of peanut-fungus interaction has not been sufficiently studied. We used pure peanut stilbenoids, arachidin-1, arachidin-3, and chiricanine A to study their effect on the viability and metabolite production by several important toxigenic Aspergillus species. Significant reduction, or virtually complete suppression of aflatoxin production was revealed in feeding experiments in A. flavus, A. parasiticus, and A. nomius. Changes in morphology, spore germination and growth rate were observed on A. flavus exposed to selected peanut stilbenoids. Elucidation of the mechanism of aflatoxin suppression by peanut stilbenoids could provide strategies for preventing plant invasion by the fungi that produce aflatoxins.
Peanuts that keep aflatoxin at bay: A threshold that matters.
Aflatoxin contamination in peanuts poses major challenges for vulnerable populations of sub-Saharan Africa and South Asia. Developing peanut varieties to combat pre-harvest Aspergillus flavus infection and resulting aflatoxin contamination has thus far remained a major challenge, confounded by highly complex peanut-Aspergilli pathosystem. Our study reports achieving high level of resistance in peanut by over expressing (OE) antifungal plant defensins MsDef1 and MtDef4.2, and through host-induced gene silencing (HIGS) of aflM and aflP genes from the aflatoxin biosynthetic pathway. While the former improves genetic resistance to A. flavus infection, the latter inhibits aflatoxin production in the event of infection providing durable resistance against different Aspergillus flavus morphotypes and negligible aflatoxin content in several peanut events/ lines well. A strong positive correlation was observed between aflatoxin accumulation and decline in transcription of the aflatoxin biosynthetic pathway genes in both OE-Def and HIGS lines. Transcriptomic signatures in the resistant lines revealed key mechanisms such as regulation of aflatoxin synthesis, its packaging and export control, besides the role of reactive oxygen species-scavenging enzymes that render enhanced protection in the OE and HIGS lines. This is the first study to demonstrate highly effective biotechnological strategies for successfully generating peanuts that are near-immune to aflatoxin contamination, offering a panacea for serious food safety, health and trade issues in the semi-arid regions.
Kinetics of aflatoxin degradation during peanut roasting.
This study investigated aflatoxin degradation during peanut roasting. First, peanuts contaminated with three initial aflatoxin concentrations (35, 332 and 695μg/kg) were roasted at 180°C for up to 20min. The percentage of aflatoxin degradation after 20min were 55, 64 and 81% for peanuts contaminated with aflatoxin at 35, 332 and 695μg/kg, respectively. This difference was statistically significant (p<0.05), showing that initial concentration influences aflatoxin reduction. Thereafter, peanut samples contaminated with an initial aflatoxin concentration of 85μg/kg were roasted at 160, 180 and 200°C for 5, 10, 15, 20 and 25min, then residual concentrations of aflatoxin were determined. Roasting at 160, 180 and 200°C resulted in an aflatoxin reduction of 61.6, 83.6 and 89.7%, respectively. This study has provided quantitative data reinforcing the fact that roasting alone is not enough to control aflatoxins in peanuts.
Occurrence, Toxicity, and Analysis of Major Mycotoxins in Food.
Mycotoxins are toxic secondary metabolites produced by certain filamentous fungi (molds). These low molecular weight compounds (usually less than 1000 Daltons) are naturally occurring and practically unavoidable. They can enter our food chain either directly from plant-based food components contaminated with mycotoxins or by indirect contamination from the growth of toxigenic fungi on food. Mycotoxins can accumulate in maturing corn, cereals, soybeans, sorghum, peanuts, and other food and feed crops in the field and in grain during transportation. Consumption of mycotoxin-contaminated food or feed can cause acute or chronic toxicity in human and animals. In addition to concerns over adverse effects from direct consumption of mycotoxin-contaminated foods and feeds, there is also public health concern over the potential ingestion of animal-derived food products, such as meat, milk, or eggs, containing residues or metabolites of mycotoxins. Members of three fungal genera, Aspergillus, Fusarium, and Penicillium, are the major mycotoxin producers. While over 300 mycotoxins have been identified, six (aflatoxins, trichothecenes, zearalenone, fumonisins, ochratoxins, and patulin) are regularly found in food, posing unpredictable and ongoing food safety problems worldwide. This review summarizes the toxicity of the six mycotoxins, foods commonly contaminated by one or more of them, and the current methods for detection and analysis of these mycotoxins.
Genotypic Regulation of Aflatoxin Accumulation but Not Aspergillus Fungal Growth upon Post-Harvest Infection of Peanut (Arachis hypogaea L.) Seeds.
Aflatoxin contamination is a major economic and food safety concern for the peanut industry that largely could be mitigated by genetic resistance. To screen peanut for aflatoxin resistance, ten genotypes were infected with a green fluorescent protein (GFP)-expressing Aspergillus flavus strain. Percentages of fungal infected area and fungal GFP signal intensity were documented by visual ratings every 8 h for 72 h after inoculation. Significant genotypic differences in fungal growth rates were documented by repeated measures and area under the disease progress curve (AUDPC) analyses. SICIA (Seed Infection Coverage and Intensity Analyzer), an image processing software, was developed to digitize fungal GFP signals. Data from SICIA image analysis confirmed visual rating results validating its utility for quantifying fungal growth. Among the tested peanut genotypes, NC 3033 and GT-C20 supported the lowest and highest fungal growth on the surface of peanut seeds, respectively. Although differential fungal growth was observed on the surface of peanut seeds, total fungal growth in the seeds was not significantly different across genotypes based on a fluorometric GFP assay. Significant differences in aflatoxin B levels were detected across peanut genotypes. ICG 1471 had the lowest aflatoxin level whereas Florida-07 had the highest. Two-year aflatoxin tests under simulated late-season drought also showed that ICG 1471 had reduced aflatoxin production under pre-harvest field conditions. These results suggest that all peanut genotypes support A. flavus fungal growth yet differentially influence aflatoxin production.
Innovative technologies to manage aflatoxins in foods and feeds and the profitability of application–A review.
Aflatoxins are mainly produced by certain strains of Aspergillus flavus, which are found in diverse agricultural crops. In many lower-income countries, aflatoxins pose serious public health issues since the occurrence of these toxins can be considerably common and even extreme. Aflatoxins can negatively affect health of livestock and poultry due to contaminated feeds. Additionally, they significantly limit the development of international trade as a result of strict regulation in high-value markets. Due to their high stability, aflatoxins are not only a problem during cropping, but also during storage, transport, processing, and handling steps. Consequently, innovative evidence-based technologies are urgently required to minimize aflatoxin exposure. Thus far, biological control has been developed as the most innovative potential technology of controlling aflatoxin contamination in crops, which uses competitive exclusion of toxigenic strains by non-toxigenic ones. This technology is commercially applied in groundnuts maize, cottonseed, and pistachios during pre-harvest stages. Some other effective technologies such as irradiation, ozone fumigation, chemical and biological control agents, and improved packaging materials can also minimize post-harvest aflatoxins contamination in agricultural products. However, integrated adoption of these pre- and post-harvest technologies is still required for sustainable solutions to reduce aflatoxins contamination, which enhances food security, alleviates malnutrition, and strengthens economic sustainability.
Co-occurrence of aflatoxins and ochratoxin A in dried fruits in Iran: Dietary exposure risk assessment.
In this study, the contamination levels of aflatoxins (AFs) and ochratoxin A (OTA) in 88 collected samples from Iran's market including dried mulberry, date, fig, and apricot were evaluated. The margin of exposure (MOE) was estimated to assess the risk of dietary intake of aflatoxin B1 (AFB1) and OTA. The incidence of AFB1 in dried mulberry, date, fig and apricot samples was 45.5, 40.9, 59.1, and 81.8%, respectively. Although the mean total AFs content in contaminated samples of date (2.61 μg/kg), fig (3.43 μg/kg) and apricot (2.91 μg/kg) was lower than the maximum limit set in the European Union (EU) (4 μg/kg), dried mulberry samples showed a higher contamination level (4.12 μg/kg). The co-occurrence of OTA and AFs were noted in 4 (18.9%), 2 (9.1%), 4 (18.2%), and 10 (45.5%) in the dried mulberry, date, fig and apricot samples, respectively. Based on the calculated MOE, the dietary exposure to AFs through the consumption of dried fruit in Iran poses a potential risk to consumer health. OTA was detected in 45.45%, 22.72%, 45.45%, and 50% of mulberry, date, fig and apricot samples, respectively. However, OTA levels in all types of dried fruit were below recommended level in EU regulation (10 μg/kg) and MOE >10000, representing no toxicological concerns for consumers.
Survey of Alternaria Toxins and Other Mycotoxins in Dried Fruits in China.
Occurrence of toxigenic molds and mycotoxins on dried fruits is a worldwide problem, but limited information is available in China. A total of 220 dried fruits (raisins, dried apricots, dates and wolfberries) purchased from China were analyzed for 17 mycotoxins (i.e., Alternaria toxins, ochratoxin A (OTA), patulin (PAT) and trichothecenes) by UPLC-MS/MS, combined with a single-step cleanup. The result showed that at least one mycotoxin was detected in 142 samples (64.6%). The lowest incidence of contaminated samples was observed in dried apricots (48.2%), and the highest incidence in dried wolfberries (83.3%). The Alternaria toxins seemed to be the major problem in dried fruits, rather than OTA or PAT. Tenuazonic acid (TeA) was the predominant mycotoxin, in both frequency and concentration, ranging from 6.9 to 5665.3 μg kg-1, followed by tentoxin (TEN; 20.5%), and mycophenolic acid (MPA; 19.5%). Moreover, raisins are more likely to be contaminated with OTA than the other dried fruits. Penicillic acid (PA) was detected only in dried dates, and PAT was detected only in one apricot sample. In addition, our results also showed that the simultaneous presence of 2-4 mycotoxins was observed in 31.4% of dried fruits. TeA and TEN were the most frequent combination, detected in 29 (13.2%) samples, followed by TeA and MPA with a prevalence of 11.4%. Therefore, the results of this survey suggest the need for wider monitoring on the contamination of these mycotoxins, especially Alternaria toxins in agro-products, and indicate the importance of setting a maximum limit for Alternaria toxins in China.