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Control of Aflatoxin Contamination Before and After Harvest

Aflatoxins are in a group of mycotoxins that are able to contaminate a range of food commodities such as grains and nuts. They are generated by some strains of Aspergillus fungi among which A. flavus and A. parasiticus prevail. The presence of aflatoxins in the ingested foods can induce chronic or acute disorders in the body which include liver cancers, chronic toxicity and mutations. The main types of aflatoxins consist of B1, B2, G1 and G2 that are characterised depending on their fluorescent colour under long wave UV light.

Aflatoxins are synthesised via enzymatic conversions that are initially attributed to the production of polypeptide from acetate. The growth of aflatoxins relies on some biological and physical factors. These include humidity, temperature, crop nutrition, storage condition, capability of the mould strain to form aflatoxins, competing microbes and the presence of growth inhibitors (such as anti-mould compounds).

It is relatively unfeasible to eliminate aflatoxins from the contaminated crops. Hence it is necessary to carry out adequate control procedures to minimise/prevent contamination in susceptible foods. The imposed regulations on the maximum limit of aflatoxins in food commodities are legally required to be adopted to reduce the incidence of contamination and ultimately to ensure the safety of foods and animal feeds. In this regard, all necessary actions should be taken before, during and after harvest including right-time harvesting (to ensure the optimum levels of moisture and maturity), control of insects, well-ventilated storage, efficient processing operations, application of anti-fungi preservatives and proper storage/delivery of the final products.

To date, numerous post-harvest strategies based on biological and physical controls have been reported to be efficient in limiting the growth of aflatoxins. For instance, the application of atoxigenic (non-toxigenic) genera such as A.flavus and A.parasiticus has shown to have the potential for the inhibition of toxigenic strains. Atoxigenic strains are able to exert competing/eliminating activities against toxigenic ones.

Furthermore, the addition of genera Bacillus subtilis to groundnuts has been found to be effective in reducing the activity of A. flavus. Many studies have also emphasised the importance of the processing and storage control methods such as moisture content, drying temperature, drying techniques, storage time and temperature. The efficiency and applicability of drying methods after harvest are highly contributory to controlling toxic development. Reduction of toxigenicity in crops and processed foods is crucial to ensure the safety and health of consumers.

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