16 research outputs found

    Polyphasic approach to the identification and characterization of aflatoxigenic strains of Aspergillus section Flavi isolated from peanuts and peanut-based products marketed in Malaysia

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    Peanuts are widely consumed as the main ingredient in many local dishes in Malaysia. However, the tropical climate in Malaysia (high temperature and humidity) favours the growth of fungi from Aspergillus section Flavi, especially during storage. Most of the species from this section, such as A. flavus, A. parasiticus and A. nomius, are natural producers of aflatoxins. Precise identification of local isolates and information regarding their ability to produce aflatoxins are very important to evaluate the safety of food marketed in Malaysia. Therefore, this study aimed to identify and characterize the aflatoxigenic and non-aflatoxigenic strains of Aspergillus section Flavi in peanuts and peanut-based products. A polyphasic approach, consisting of morphological and chemical characterizations was applied to 128 isolates originating from raw peanuts and peanut-based products. On the basis of morphological characters, 127 positively identified as Aspergillus flavus, and the other as A. nomius. Chemical characterization revealed six chemotype profiles which indicates diversity of toxigenic potential. About 58.6%, 68.5%, and 100% of the isolates are positive for aflatoxins, cyclopiazonic acid and aspergillic acid productions respectively. The majority of the isolates originating from raw peanut samples (64.8%) were aflatoxigenic, while those from peanut-based products were less toxigenic (39.1%). The precise identification of these species may help in developing control strategies for aflatoxigenic fungi and aflatoxin contamination in peanuts, especially during storage. These findings also highlight the possibility of the co-occurrence of other toxins, which could increase the potential toxic effects of peanuts

    Prevalence of Aspergillus spp. and occurrence of aflatoxins in peanut sauce processing by peanut sauce manufacturers

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    The aims of the present work were to determine the prevalence of Aspergillus spp. and occurrence of aflatoxins (AFs) along the peanut sauce processing line from different peanut sauce companies in Malaysia, and to determine to which extent peanut sauce processing steps employed by the peanut sauce industries could efficiently reduce AFs in peanut sauce. Peanut and chili samples were collected at each processing step along the peanut sauce production from three peanut sauce companies which were different in companies’ profile. Peanut samples from Companies B (87.5%) and C (100%) were contaminated with AFs. Of these, 12.5% (Company B) and 75% (Company C) samples exceeded the Malaysian regulatory limit. None of the samples from Company A was contaminated. The steps efficient in reducing AFs in peanut sauce identified in the present work were (i) safety monitoring of raw materials, (ii) sorting of raw materials, and (iii) heat treatment of raw materials

    Formulation of maize- and peanut-based semi-synthetic growth media for the ecophysiological studies of aflatoxigenic Aspergillus flavus in maize and peanut agro-ecosystems

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    In studying the ecophysiology of fungal phytopathogens, several stages are involved (in vitro, greenhouse, in planta). Most in vitro studies extensively utilise the general growth media such as Potato Dextrose Agar and Malt Extract Agar. Although the crop components in these media serve as excellent carbon sources and yield luxuriant growth, they are not naturally contaminated with Aspergillus flavus and thus might result in under- or overestimation of its actual toxigenic potentials. Empirical data on the formulation of semi-synthetic growth medium mimicking the natural crop commonly contaminated by A. flavus for the ecophysiological studies in vitro are scarce. The present work was aimed at investigating the ecophysiology of A. flavus on commercial growth media (PDA, MEA); formulating maize- and peanut-based semi-synthetic growth media using two methods of raw material preparation (milling, hot water extraction) at different concentrations (1, 3, 5, 7, 9% w/v), and comparing the ecophysiological parameters between commercial and formulated growth media. Growth rates were obtained by computing the hyphal expansion data into y = mx + c equation. AFB1 was quantified using high performance liquid chromatography with fluorescence detector. Formulated media were found to yield significantly higher growth rates when compared to commercial media. However, commercial media yielded significantly higher AFB1 when compared to all formulated media. Between the two formulations, milling yielded significantly higher growth rates and AFB1 when compared to hot water extraction. Although in vitro data cannot directly extrapolate in planta performance, results obtained in the present work can be used to gauge the actual toxigenic potential of A. flavus in maize and peanut agro-ecosystems

    Evaluation of aflatoxin and Aspergillus sp. contamination in raw peanuts and peanut-based products along this supply chain in Malaysia

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    The peanut supply chain in Malaysia is dominated by three main stakeholders (importers, manufacturers, retailers). The present study aimed to determine the levels and critical points of aflatoxin and fungal contamination in peanuts along the supply chain. Specifically, two types of raw peanuts and six types of peanut-based products were collected (N = 178). Samples were analysed for aflatoxins by using high-performance liquid chromatography. Results revealed that the aflatoxin contamination was significantly higher (P ≤ 0.05) in raw peanuts and peanut-based products from the retailers. However, there was no significant difference (P ≥ 0.05) in fungal contamination for both types of peanuts except for the total fungal count in raw peanuts from the retailers. Furthermore, raw peanut kernels from the retailers were the most contaminated ones ranged from <LOD to 1021.4 µg/kg (mean: 120.7 µg/kg, median: 1.4 µg/kg) followed by the samples collected from the manufacturers which was ranged from < LOD to 181.9 µg/kg (mean: 20.5 µg/kg, median: 0.0 µg/kg). About 38% and 22% of the samples from the retailers and manufacturers were found to have exceeded the Malaysian Regulation limit (raw peanuts:15 µg/kg; peanut-based products:10 µg/kg), respectively. In contrast, no aflatoxins were detected in samples from the importers. On the other hand, 15.0% and 5.9% of peanut-based products from retailers and manufacturers, respectively, were found to have exceeded the limit. Fungal contamination (0.3–3.6 log CFU/g) was relatively higher in raw peanuts compared to that of peanut-based products (0.6–2.7 log CFU/g). In conclusion, the manufacturers and retailers were the critical points for aflatoxin contamination in peanuts. However, fungal contamination was more critical in the raw peanuts compared to peanut-based products. The study was limited by a minimal number of samples from the importer. Therefore, further investigations on a larger sample size should be conducted to confirm the findings in this present study

    Evaluation, characterisation and modelling of Aspergillus flavus in aflatoxin production in peanuts along the supply chain

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    Aflatoxin contamination is a major food safety issue in raw peanuts and peanut-based products worldwide. Thus, an extensive study on aflatoxins and Aspergillus spp. in peanuts along the supply chain in Malaysia is needed in order to protect the consumers against the harmful effects of aflatoxins. Generally, this study was aimed to evaluate the aflatoxin contamination, identify, characterise and model the growth of aflatoxigenic A. flavus isolated from peanuts collected from the importers, manufacturers, and retailers. In the present study, aflatoxins were found to be significantly higher (p < 0.05) in raw peanuts and peanut-based products from the retailers (< LOD – 1021.4 μg/kg) followed by the manufacturers (< LOD – 181.9 μg/kg) while samples from the importers were free from aflatoxins. Total fungal count was relatively higher in raw peanuts (log 0.3 – 3.6 CFU/g) as compared to peanutbased products (log 0.6 – 2.3 CFU/g) in which samples from the importers recorded the highest contamination level for aflatoxigenic Aspergillus spp. (log 2.2 ± 1.1 CFU/g). On the basis of morphological, chemical, and molecular identification, all isolates were identified as Aspergillus section Flavi. Specifically, 127 isolates were confirmed as A. flavus, and one isolate as A. tamarii. Six chemotype profiles were proposed indicating the diversity of toxigenic potential. About 58.6%, 68.5%, and 100% of the isolates were positive for aflatoxin, cyclopiazonic acid and aspergillic acid production, respectively. The maximum likelihood (ML) phylogenetic tree using ITS and β-tubulin gene resolved the species into two different clades in which all A. flavus (both aflatoxigenic and non-aflatoxigenic) were grouped in the same clade and A. tamarii in a different clade. Aflatoxin biosynthesis genes namely aflR, aflP (omtA), aflD (nor-1), aflM (ver-1), and aflC (pksA) were detected in all aflatoxigenic A. flavus while the non-aflatoxigenic A. flavus failed to amplify at least one of the genes that was tested. The analysis of variance showed a significant effect of strain, temperature and water activity (aw) on the fungal growth and aflatoxin production (p < 0.05). The maximum growth rate, μmax (mm/day) of two aflatoxigenic A. flavus, (A8R and A82R) on PMEA was estimated by using the primary model of Baranyi and the μmax was then fitted to the secondary model; second order polynomial and linear Arrhenius-Davey to describe the growth rate as a function of temperature and aw. In general, the growth rate of A. flavus increased with increasing temperature and aw until reaching the optimum temperature and further increase in aw beyond this point resulted in decrease growth rate. The growth of A. flavus was observed at the minimum aw of 0.85 under the optimum temperature (32 – 33°C) and the minimum temperature of 20°C with 0.94 aw. A similar pattern was observed in aflatoxin production but in a narrower range of temperature (25 – 35°C) and aw (0.92 – 0.98 aw). In conclusion, A. flavus was the predominant species that contaminate peanuts and subsequently produce aflatoxins during the storage period. Therefore, proper storage structures and conditions for peanuts during storage are very important in order to control the growth of aflatoxigenic A. flavus and aflatoxin contamination

    <i>Salmonella</i> spp. in Chicken: Prevalence, Antimicrobial Resistance, and Detection Methods

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    Multidrug-resistant Salmonella spp. is one of the leading causes of worldwide foodborne disease outbreaks. Animal-derived foods, particularly chicken and poultry products, are the most likely source of Salmonella transmission to humans. The increasing demand for chicken meat has raised a global food safety issue. This review aims to determine the prevalence and antimicrobial resistance of Salmonella spp. in chickens from various countries in Asia. The methods for detecting Salmonella will also be discussed in this review. The prevalence of Salmonella spp. in chicken and poultry products is lower in developed countries than in developing countries. In addition, the incidence of Salmonella spp. in chicken and poultry products from fresh markets is higher than those from supermarkets. Furthermore, this review also reported the presence of multidrug-resistant Salmonella strains in various Asian countries. Rapid Salmonella detection based on immunological assays, molecular-based assays, and biosensors can provide more accurate results with high sensitivity and specificity. These methods also require a shorter time than the cultural-based Salmonella detection method. The use of suitable detection methods to determine the presence of Salmonella spp. in chicken and poultry products is important to ensure food safety

    Salmonella spp. in Chicken: Prevalence, Antimicrobial Resistance, and Detection Methods

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    Multidrug-resistant Salmonella spp. is one of the leading causes of worldwide foodborne disease outbreaks. Animal-derived foods, particularly chicken and poultry products, are the most likely source of Salmonella transmission to humans. The increasing demand for chicken meat has raised a global food safety issue. This review aims to determine the prevalence and antimicrobial resistance of Salmonella spp. in chickens from various countries in Asia. The methods for detecting Salmonella will also be discussed in this review. The prevalence of Salmonella spp. in chicken and poultry products is lower in developed countries than in developing countries. In addition, the incidence of Salmonella spp. in chicken and poultry products from fresh markets is higher than those from supermarkets. Furthermore, this review also reported the presence of multidrug-resistant Salmonella strains in various Asian countries. Rapid Salmonella detection based on immunological assays, molecular-based assays, and biosensors can provide more accurate results with high sensitivity and specificity. These methods also require a shorter time than the cultural-based Salmonella detection method. The use of suitable detection methods to determine the presence of Salmonella spp. in chicken and poultry products is important to ensure food safety

    Antagonism of nonaflatoxigenic Aspergillus flavus isolated from peanuts against aflatoxigenic A. flavus growth and aflatoxin B1 production in vitro

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    Abstract Aspergillus section Flavi constitutes several species of opportunistic fungi, notable among them are A. flavus and A. parasiticus, capable of surviving harsh conditions and colonizing a wide range of agricultural products pre‐ and postharvest. Physical and chemical control methods are widely applied in order to mitigate the invasion of A. flavus in crops. However, physical control is not suitable for large scale and chemical control often leads to environmental pollution, whereas biological control offers a safer, environmentally friendly, and economical alternative. The present study aimed to investigate the antagonism of several non‐aflatoxigenic A. flavus strains against the aflatoxigenic ones in vitro (semisynthetic peanut growth medium; MPA) in terms of colony growth rate and AFB1 inhibition. Different peanut concentrations were used to obtain the optimum peanut concentration in the formulated growth medium. A dual culture assay was performed to assess the antagonism of nonaflatoxigenic strains against the aflatoxigenic ones. Results revealed that 9% MPA exhibited the highest growth and AFB1 inhibition by nonaflatoxigenic strains. It was also found that different nonaflatoxigenic strains exhibited different antagonism against the aflatoxigenic ones which ranged from 11.09 ± 0.65% to 14.06 ± 0.14% for growth inhibition, and 53.97 ± 2.46% to 72.64 ± 4.54% for AFB1 inhibition. This variability could be due to the difference in antagonistic metabolites produced by different nonaflatoxigenic strains assessed in the present study. Metabolomics study to ascertain the specific metabolites that conferred the growth and aflatoxin inhibition is ongoing

    Aspergillus section Flavi and aflatoxins: occurrence, detection, and identification in raw peanuts and peanut-based products along the supply chain

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    Aflatoxin contamination in foods is a global concern as they are carcinogenic, teratogenic and mutagenic compounds. The aflatoxin-producing fungi, mainly from the Aspergillus section Flavi, are ubiquitous in nature and readily contaminate various food commodities, thereby affecting human’s health. The incidence of aflatoxigenic Aspergillus spp. and aflatoxins in various types of food, especially raw peanuts and peanut-based products along the supply chain has been a concern particularly in countries having tropical and sub-tropical climate, including Malaysia. These climatic conditions naturally support the growth of Aspergillus section Flavi, especially A. flavus, particularly when raw peanuts and peanut-based products are stored under inappropriate conditions. Peanut supply chain generally consists of several major stakeholders which include the producers, collectors, exporters, importers, manufacturers, retailers and finally, the consumers. A thorough examination of the processes along the supply chain reveals that Aspergillus section Flavi and aflatoxins could occur at any step along the chain, from farm to table. Thus, this review aims to give an overview on the prevalence of Aspergillus section Flavi and the occurrence of aflatoxins in raw peanuts and peanut-based products, the impact of aflatoxins on global trade, and aflatoxin management in peanuts with a special focus on peanut supply chain in Malaysia. Furthermore, aflatoxin detection and quantification methods as well as the identification of Aspergillus section Flavi are also reviewed herein. This review could help to shed light to the researchers, peanut stakeholders and consumers on the risk of aflatoxin contamination in peanuts along the supply chain
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