**2.2. Aflatoxin management**

#### *2.2.1. Pre-harvest aflatoxin prevention/reduction*

Although pre-, peri, and post-harvest aflatoxin management strategies; have been itemized as different from awareness creation, knowledge of these strategies is important for awareness. For pre-harvest aflatoxin management to receive contextual appreciation it is important to understand how aflatoxin contamination occurs. Natural contamination of food by aflatoxins requires contamination by aflatoxigenic strains of *Aspergilli.* Aflatoxin-producing strains of the *Aspergillus* section *Flavi* group such as *Aspergillus flavus, A. parasiticus, A. nominus* and S strains are responsible for contamination. Recently, a novel aflatoxin producer called *A. korhogoensis* (defined as a "*a novel cryptic species within the A. flavus clade*" was identified in Côte d'Ivoire [33]. Route of contamination is typically one by which the spores of these strains can enter the grains. Fungal spores reside on crop debris, in soils and can be air-borne when dispersed by wind. Spores can also be carried by insects and birds directly to the grains and thereby contaminate them [34–36].

To this end, methods that serve as barriers in preventing aflatoxigenic fungi from gaining entrance into the crop are critical for the control of aflatoxin contamination. For the maize during crop development, spores can enter grains via the silk channel (each silk thread leads to a kernel of maize), through cracks in the kernel because of abiotic stress such as heat or drought, and biotic stresses such as insects or birds [34, 37]. Furthermore, reducing the populations of the aflatoxin-producers in the environment can also reduce the risk of human exposure to aflatoxin. Pre-harvest management of aflatoxin contamination therefore comprises:

• Breeding efforts that increase the barriers to aflatoxigenic fungi [38]. These have been explored through increased tightness of husk cover and increased hardness of grains. These reduce the possibility of fungal entry into the grain and therefore aflatoxin contamination. However, flint grains (very hard grains) are difficult to process and because of that, farmers are not always willing to grow these varieties. Gene silencing as a method for aflatoxin management was recently developed by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) [39]. However, acceptance of genetic modification of foods in and for sub-Saharan Africa has not received wide acceptance.


While mold contamination is known in many parts of sub-Saharan Africa because of their visual presentation and bitter taste, the aflatoxins that they produce are frequently unknown because they lack sensory attributes. Therefore, moldy grains would attract lesser value, while grains without visible mold, are not necessarily without aflatoxin contamination. Therefore, it is not uncommon for these grains to be used in the processing of food or feed material in which mold appearance is masked. This is for instance, in the processing of peanut butter, groundnut cake, poultry feed and fermentation for beers [40–43]. However, this is not a good management technique for aflatoxins as these poor-quality grains enter the food chain as alternative food products and the processing techniques may either minimally reduce the aflatoxins or concentrate the aflatoxins. However, visual signs of mold are not the only indicators of fungal infestation. It is possible for strains that produce high levels of aflatoxins to mildly infected grains, resulting in high aflatoxin levels. Also, grains contaminated with aflatoxins that have been washed and dried after infection, may no longer have visible mold growth but still contain the aflatoxins. This is because aflatoxins are only very mildly soluble in water at 10 mg/ml and are heat stable up to 150°C, after which they are only mildly detoxified [44].

#### *2.2.2. Peri-harvest aflatoxin prevention/reduction*

*2.1.1.5. Other awareness platforms*

116 Mycotoxins - Impact and Management Strategies

ment strategy.

**2.2. Aflatoxin management**

*2.2.1. Pre-harvest aflatoxin prevention/reduction*

and thereby contaminate them [34–36].

Online documentation (e.g. websites, blogs, social networks), field extension services, commercial organizations and word of mouth are also important avenues of awareness creation. Dissemination of information via traditional media such as newspaper publications, radio broadcasts and discussions are also important for ensuring that the population gets the required information and to gauge the level of awareness/responses to the sensitization efforts. It is important that these efforts continue where already in place and make-up concerted efforts that are contributory to awareness creation as an important aflatoxin manage-

Although pre-, peri, and post-harvest aflatoxin management strategies; have been itemized as different from awareness creation, knowledge of these strategies is important for awareness. For pre-harvest aflatoxin management to receive contextual appreciation it is important to understand how aflatoxin contamination occurs. Natural contamination of food by aflatoxins requires contamination by aflatoxigenic strains of *Aspergilli.* Aflatoxin-producing strains of the *Aspergillus* section *Flavi* group such as *Aspergillus flavus, A. parasiticus, A. nominus* and S strains are responsible for contamination. Recently, a novel aflatoxin producer called *A. korhogoensis* (defined as a "*a novel cryptic species within the A. flavus clade*" was identified in Côte d'Ivoire [33]. Route of contamination is typically one by which the spores of these strains can enter the grains. Fungal spores reside on crop debris, in soils and can be air-borne when dispersed by wind. Spores can also be carried by insects and birds directly to the grains

To this end, methods that serve as barriers in preventing aflatoxigenic fungi from gaining entrance into the crop are critical for the control of aflatoxin contamination. For the maize during crop development, spores can enter grains via the silk channel (each silk thread leads to a kernel of maize), through cracks in the kernel because of abiotic stress such as heat or drought, and biotic stresses such as insects or birds [34, 37]. Furthermore, reducing the populations of the aflatoxin-producers in the environment can also reduce the risk of human exposure to

• Breeding efforts that increase the barriers to aflatoxigenic fungi [38]. These have been explored through increased tightness of husk cover and increased hardness of grains. These reduce the possibility of fungal entry into the grain and therefore aflatoxin contamination. However, flint grains (very hard grains) are difficult to process and because of that, farmers are not always willing to grow these varieties. Gene silencing as a method for aflatoxin management was recently developed by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) [39]. However, acceptance of genetic modification of foods in

aflatoxin. Pre-harvest management of aflatoxin contamination therefore comprises:

and for sub-Saharan Africa has not received wide acceptance.

During harvest, exposure to aflatoxin contamination can occur due to practices that expose the crop to aflatoxigenic fungi as it is harvested. These could include harvesting during the rains or during high moisture conditions that encourage fungal proliferation; harvesting into recycled or contaminated containers such as bags, and carts that harbor the toxigenic mold or insects, or directly onto uncovered ground surfaces, threshing during harvest in a way that damages the grains. Preventing these would therefore involve the use of clean surfaces or containers for placement of harvested grains and rapid drying after harvest to avoid incubation of the fungus and subsequent accumulation of the toxin.

#### *2.2.3. Post-harvest aflatoxin prevention/reduction*

Post-harvest practices occur immediately after harvesting grain produce. These practices are inclusive of practices undertaken such as transportation, storage and processing of the harvested agricultural produce. As with peri-harvest practices, it is important to prevent predisposing factors such as pest infestation, re-contamination from re-used bags or improperly sanitized vessels or vehicles. It is therefore critical to ensure proper pest control, good aeration by placing stored grains in dry and well aerated storehouses. The use of wooden pallets, and away from walls, rather than placing bags in direct contact with floor surfaces and walls limits aflatoxin accumulation in hot spots. Other important post-harvest practices for reducing contamination include winnowing and sorting of grains to remove low density materials and grains that tend to harbor high proportions of the contaminated material [45].

**Author details**

Address all correspondence to: t.falade@cgiar.org

DOI: 10.1016/b978-0-12-385926-6.00102-2

Mortal. Wkly. Rep. January to July 2004;**53**:790-793

2010;**19**:516-521. DOI: 10.1111/j.1365-2354.2009.01087.x

2015;**123**:173-178. DOI: 10.1289/ehp.1408097

DOI: 10.1080/19440049.2012.688878

International Institute of Tropical Agriculture, Ibadan, Nigeria

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Titilayo Falade

**References**

ps.2012-02748

#### *2.2.4. Post-contamination aflatoxin management*

Post-contamination management strategies are implemented when all attempts of reducing aflatoxin levels to permissible limits have failed. It is not recommended as a strategy without attempts to prevent contamination. There are controversies surrounding the implementation of some of these practices for the management of aflatoxins. Some of the practices include dilution with non-contaminated grains to reduce bulk contamination, ammoniation [46], binding of aflatoxins using adsorbents or aflatoxin-binders used for animal feed [47], nixtamalization [48], grain fermentation, radiation (including solar radiation) [49], grading to allow higher levels for non-dairy ruminants up to permissible levels, or use as alternative non-food uses such as production of bio-ethanol.

#### **2.3. Conclusion**

Aflatoxin management, including continuous public awareness and monitoring is required both on-farm and off-farm. Awareness is a critical stage of management and covers preharvest, peri-harvest, post-harvest stages of crop production. Post-contamination options are the last alternative to aflatoxin management and is the least preferred method for aflatoxin management in food and feed grains due to other associated risks of contaminant fate. The most preferred method is to prevent entry of aflatoxin-producing fungal strains, then limiting the ability of contaminating aflatoxin-producing strains from synthesizing and accumulating the harmful toxins in food grains. With proper aflatoxin-management, health and income improvement will increase in sub-Saharan Africa – a region with a high perennial risk of aflatoxin exposure, thus boosting the health of the people within the region.
