Inactivation aflatoxins

A wide range of chemicals have been tested for the ability to degrade and inactivate aflatoxins. However, although a number of these chemicals can react to destroy aflatoxins effectively, most are impractical, too expensive or potentially unsafe because of the formation of toxic residues, or the perturbation of the nutrient content of the food. Two chemical approaches that have received considerable attenhon are ammoniation and reaction with sodium bisulphite. 

In summary, our observations that many structurally different thiols can suppress the mutagenic activity of aflatoxin B. suggest that thiols may be useful for inactivating aflatoxins in contaminated foods, as an,antidote to treat cases of aflatoxin toxicity, or for prophylaxis to prevent aflatoxin poisoning. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Procedures aimed at reducing or detoxifying aflatoxins and/or their effects have been reviewed by Phillips et al. (35), and include technological procedures for food and feeds and chemical degradation, as well as biocontrol and microbial inactivation, dietary modification and chemoprotection, and reduction in toxin bioavailability via selective chemisorption with clay. 

Chemical detoxification processes or decontamination will include degradation, destmction and/or inactivation of the mycotoxin. In any such process the reduction of the mycotoxin to safe levels should not result in toxic degradation products or reduce the palatability or nutritional properties of the commodities. Aflatoxin has been the subject of most studies and only a relatively small number of these offers any hope of success. There is as yet no FDA or EC fully approved method for aflatoxin detoxification in human foods. Current methods in advanced stages of approval use ammonia in the gaseous form or as an ammonium hydroxide solution at various temperatures, pressure, moisture contents and reaction time to degrade aflatoxins in various animal feedstuffs. There have been extensive studies using two processes, viz ... 

Hajare, S.S., Hajare, S.N. and Sharma, A. (2005) Aflatoxin inactivation using aqueous extract of ajowan (Trachyspermum ammi) seeds, journal of Food Science 70(1), C29-C34. 

Because it is impossible to completely avoid some degree of aflatoxin contamination, a variety of strategies for their detoxification in foodstuffs have been proposed. These strategies have included physical methods of separation, thermal inactivation, irradiation, solvent extraction, adsorption from solution, microbial inactivation, chemical methods of inactivation and fermentation. Two of these strategies are described in more detail below. 

Rustom, I.Y.S. (1997) Aflatoxin in food and feed occurrence, legislation and inactivation by physical methods. Food Chem. 59, 57-67. 

Figure 6. Effect of thiol concentration on time of inactivation of mutagenic activity of aflatoxin B-j by reduced glutathione,...

Although no attempt was made to establish the order of reaction, our results show that the inactivation of mutagenic activity, and presumably the interaction of the thiols with aflatoxin, are concentration dependent. Since addition of thiols to double bonds follows second-order kinetics (Friedman et a1., 1965), this is probably also true for addition of a thiol to the 2,3 double bond of aflatoxin. 

Thiols such as cysteine, N-acetyl-cysteine, mercatoproplonyl-glyclne, and reduced glutathione Inactivate the mutagenic properties of aflatoxin B- by forming adducts at the electrophilic... 

The following experiment was carried out to test inactivation of aflatoxin Mi in milk with u.v. A 40 g sample of freeze-dried experimental milk from the cow receiving a daily dose of 80 mg aflatoxin Bi was used The dried milk had 1400 ppb aflatoxin Mi The 40 g sample was reconstituted to a volume of 400 ml with distilled water in a blender and then divided equally into two Pyrex trays (base 38 x 24 cm) giving a milk layer depth of about 2 mm One sample was kept in the dark and the other was exposed in the tray for one hour to long and short wavelength ultraviolet from a source placed about 10 above the tray in a Chromatoview cabinet. Both samples were then worked up side by side to determine aflatoxin M content according to our method... 

Inactivation of Aflatoxin Mi in Milk with Ultraviolet Light... 

Friedman, M., Wehr, C. M., Schade, J. E. and MacGregor, J. T. (1982b). Inactivation of aflatoxin Bi mutagenicity by thiols. Food and Chemical Toxicology, 20 887-892. 

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