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    Sources and Prevalence of Aflatoxin B1 in Different Rice Paddies of Punjab and Sindh, Pakistan
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    Abstract:
    Rice is a major cash crop used all over world. The hygroscopic nature of rice kernel with warm and fumic conditions is favorable to enhance the growth and development of toxigenic fungi which produce mycotoxins. This study estimates the prevalence of aflatoxin B1 in different rice paddies collected from twelve regions of the Punjab and Sindh provinces of Pakistan. All the samples were analyzed for their phenotypic characteristics (appearance, odor, and grain length). Competitive Enzyme Linked Immuno Sorbent Assay (ELISA) was used to evaluate AFB1, both before and after applying the steam decontamination procedure to detoxify aflatoxin contamination. Cultural assay was used to find the source of aflatoxin. PDA and SDA agar were used to detect aflatoxin producing fungal species. Lactophenol Cotton Blue (LCB) staining was used for microscopic identification of fungal contaminants. Paddies from most regions appeared yellowish in color and odorless with the exception of Hafizabad, Jhang, Sheikhupura, and Gujarat (in Punjab), where they appeared blackish yellow in color and with a pungent smell. According to the results, 43 (61.42%) samples were detected with aflatoxin B1 out of 70 samples, with an average of 15.86±1.7 ug/kg, before treating with seam. After treatment with steam, 7 (10%) samples were detected with aflatoxin B1, with an average of 2.55±1.51 ug/kg. Most regions showed the presence of P. chrysogenum with the exception of R.Y. Khan, which showed the presence of A. niger. Steam, on average, reduced aflatoxin to 51.42%. The current study indicates that steam is an effective treatment to eradicate aflatoxin at industrial level. New approaches may be explored to target the contaminants in order to ensure food safety.
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    Potato dextrose agar
    Dried fruits are susceptible products for mold contamination and growth, and consequent mycotoxin production. Numerous studies revealed high incidences or high levels of contamination of these products with mycotoxins. Once the product is contaminated, decontamination procedures are inevitable. Ozonation, a recently approved process in the food industry, has revealed promising results in detoxifying contaminated products. This review presents the results of recent studies conducted on mycotoxin contamination in economically important dried fruits and gives some information about contamination steps, mechanisms, and possible prevention methods for each product. The potential of ozone application in mycotoxin degradation was reviewed and finally data obtained from recent studies about the properties of degradation products after the reaction between ozone and mycotoxins was discussed.
    Human decontamination
    Food contaminant
    It is well known that cattle ingesting aflatoxin B1 contaminated feed commodities excrete aflatoxin M1 into their milk. As aflatoxin M1 originates from hepatic metabolism, measures to prevent aflatoxin M1 formation need to be directed to either the immobilization of aflatoxin B1 in the gastrointestinal tract or the modification of hepatic metabolism of aflatoxin B1. Here we studied the influence of oltipraz and a second dithiolthione, (1,2) dithiolo (4,3-c)-1,2-dithiole-3,6 dithione (DDD) on bovine hepatic aflatoxin B1 biotransformation. Oltipraz inhibited aflatoxin B1 metabolism as no aflatoxin M1 and no aflatoxin B1-dihydrodiol, the second metabolite found in bovine hepatocytes, was formed. DDD did not significantly inhibit aflatoxin B1 metabolism. It could be demonstrated that the inhibition of aflatoxin B1 metabolism was due to the inhibition of several cytochrome P450 enzyme activities by oltipraz. In contrast, DDD inhibited only ethoxyresorufin O-deethylation activity. These findings suggest a high efficacy of oltipraz in inhibiting aflatoxin M1 contamination of milk from dairy cows exposed to aflatoxin B1 contaminated feeds.
    Biotransformation
    In this study, a sensitive and accurate immunoaffinity columns coupled with high-performance liquid chromatography method was established to monitor the presence of aflatoxins-aflatoxin B1 , aflatoxin B2 , aflatoxin G1 , and aflatoxin G2 -in different medicinal herbs. The proposed method was found to be suitable for the detection of aflatoxins in eight kinds of herbs and their corresponding granules. Two batches of Arecae semen were positive for aflatoxins, with high residue levels of different aflatoxins. To better understand the presence and transfer of aflatoxins during the formulation of dispensing granules from the herbs, the aflatoxins-free herbs were artificially inoculated with Aspergillus flavus to explore aflatoxins production. Both aflatoxin B1 and aflatoxin B2 were detected in all inoculated samples, while aflatoxin G2 was only detected in Astragali radix samples. Additionally, the presence of aflatoxin B1 was extremely high compared to other aflatoxins. More specifically, the transfer rate of the aflatoxin B1 and the total aflatoxins from original herbs to granules were both approximately 40%. These findings indicated that the preparation of herbs into dispensing granules reduced the content of aflatoxins. The high-level presence of aflatoxins in inoculated herbs indicated that attention is needed to the safety of A. flavus-contaminated herbs.
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    Two aflatoxin-producing isolates of Aspergillus flavus were grown for 5 days on Wort media at 2, 7, 13, 18, 24, 29, 35, 41, 46, and 52 C. Maximal production of aflatoxins occurred at 24 C. Maximal growth of A. flavus isolates occurred at 29 and 35 C. The ratio of the production of aflatoxin B 1 to aflatoxin G 1 varied with temperature. Aflatoxin production was not related to growth rate of A. flavus ; one isolate at 41 C, at almost maximal growth of A. flavus , produced no aflatoxins. At 5 days, no aflatoxins were produced at temperatures lower than 18 C or higher than 35 C. Color of CHCl 3 extracts appeared to be directly correlated with aflatoxin concentrations. A. flavus isolates grown at 2, 7, and 41 C for 12 weeks produced no aflatoxins. At 13 C, both isolates produced aflatoxins in 3 weeks, and one isolate produced increasing amounts with time. The second isolate produced increasing amounts through 6 weeks, but at 12 weeks smaller amounts of aflatoxins were recovered than at 6 weeks.
    Mycotoxins are toxic secondary metabolites and most mycotoxins produced by filamentous fungi can grow on food, especially before harvest and in storage. When humans and animals eaten, inhaled or absorbed through the skin mycotoxins, it can cause illness or death to humans and animals. There are 20 groups of secondary metabolites of fungal aflatoxins but only four identified aflatoxin in foods that aflatoxin B1 (AFB1), Aflatoxin B2 (FB2), Aflatoxin G1 (AFG1) and Aflatoxin G2 (AFG2) (Polychronaki et al., 2008: Liu, Y., and Wu, F.2010) A COMPARATIVE
    Fungal growth
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