IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

3.2 Chemical methods
The alkali process usually practised to produce refined table oil completely removes
aflatoxin (ICMSF, 1996).
The use of chemicals to inactivate, bind or remove aflatoxins has been studied extensively.
Any such procedure must effectively inactivate or remove the toxin, while maintaining
the nutritional and technological properties of the product and without generating
toxic reaction products (López-García & Park, 1998). Food safety demonstration studies
must be conducted to ensure compliance with regulatory requirements. To date, these
chemical methods have been approved only for the reduction of aflatoxins in animal feed
commodities. Reacting the toxin chemically with another compound intentionally introduced
in the vicinity of the toxin molecule holds the greatest promise for rapid and effective
removal or inactivation of aflatoxin. Among such techniques are the use of chemosorbents
and ammoniation. Other than the demonstrated reduction in bioavailability of
aflatoxin as a result of hydrated sodium calcium aluminosilicate binding (Phillips et al.,
1988), ammoniation is the only chemical inactivation process that has been shown to
destroy aflatoxin efficiently in cottonseed and cottonseed meal, peanuts and peanut meal
and maize (Park et al., 1988; Park & Price, 2001).
3.2.1 Aflatoxin-binding agents
Adsorption of aflatoxin using activated carbons, clays and aluminosilicates has been
demonstrated in a number of studies. Bentonite clays (Masimango et al., 1979) and
activated charcoal (Decker, 1980), both used in oil purification, can adsorb up to 92% of
aflatoxin present. A phyllosilicate clay currently used as an anti-caking agent has been
shown to bind aflatoxin tightly and diminish markedly its uptake into the circulatory
system, preventing aflatoxicoses and reducing levels of aflatoxin M 1 in milk (Phillips
et al., 1988). The specificity of the clays and their potential for binding nutrients in addition
to aflatoxin remains a concern. Further research is required to determine whether
these materials can be used in human foods.
3.2.2 The ammoniation process
ANNEX 285
The ammoniation process has been used to reduce aflatoxin levels in feed ration
components in order to prevent the presence of aflatoxin in tissues and animal products
such as milk. In the USA, the States of Arizona, California and Texas permit the ammoniation
of cottonseed products. Texas has, in addition, approved the ammoniation procedure
for aflatoxin-contaminated corn, but the treated corn may only be used in finishing
beef cattle diets. Ammoniation is used in Brazil, France, Mexico, Senegal, Sudan and
some states of the USA to lower aflatoxin contamination levels in animal feeds. The two
procedures in widespread use are: (a) a high-pressure and high-temperature process
(HP/HT) used at treatment plants, and (b) an atmospheric-pressure and ambient-temperature
procedure (AP/AT) that can be used on the farm (Table 2). The HP/HT process