**1. Introduction**

Mycotoxins are natural contaminants in raw materials, food and feeds [1]. Aflatoxins are toxic metabolites produced by different species of toxigenic fungi, called mycotoxins. The discovery of aflatoxins dates back to the year 1961 following the severe outbreak of turkey "X" disease, in the England, which resulted in the deaths of more than 100.000 turkeys and other farm animals. The cause of the disease was attributed to a feed using thin-layer chro‐ matography (TLC) revealed that a series of fluorescent compounds, later termed aflatoxins, were responsible for the outbreak. The disease was linked to a peanut meal, incorporated in the diet, contaminated with a toxin produced by the filamentous fungus *Aspergillus flavus.* Hence, the name aflatoxins, an acronym, has been formed from the following combination: the first letter, "A" for the genus *Aspergillus*, the next set of three letters, "FLA", for the spe‐ cies *flavus*, and the noun "TOXIN" meaning poison [2].

Aflatoxins (AFs) are difuranocoumarins produced primarily by two species of *Aspergillus* fungus which are especially found in areas with hot, humid climates. *A. flavus* is ubiquitous, favouring the aerial parts of plants (leaves, flowers) and produces B aflatoxins. *A. parasiticus* produces both B and G aflatoxins, is more adapted to a soil environment and has more limit‐ ed distribution [3]. *A. bombysis*, *A. ochraceoroseus*, *A. nomius*, and *A. pseudotamari* are also AFsproducing species, but are encountered less frequently. From the mycological perspective, there are qualitative and quantitative differences in the toxigenic abilities displayed by dif‐ ferent strains within each aflatoxigenic species. For example, only about half of *A. flavus* strains produce AFs-producing species more than 106 µg kg−1 [4].

Among the 18 different types of aflatoxins identified, the major members are aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), M1 (AFM1) and M2 (AFM2). AFB1 is normally predominant in amount in cultures as well as in food products. Pure AFB1 is pale-white to yellow crystalline, odorless solid. AFs are soluble in methanol, chloroform, acetone, acetoni‐

trile. *A. flavus* typically produces AFB1 and AFB2, whereas *A. parasiticus* produce AFG1 and AFG2 as well as AFB1 and AFB2. Four other aflatoxins M1, M2, B2A, G2A which may be produced in minor amounts were subsequently isolated from cultures of *A. flavus* and *A. parasiticus*. A number of closely related compounds namely aflatoxin GM1, parasiticol and aflatoxicol are also produced by *A. flavus.* The order of acute and chronic toxicity is AFB1 > AFG1 > AFB2 > AFG2, reflecting the role played by epoxidation of the 8,9-double bond and also the greater potency associated with the cyclopentenone ring of the B series, when com‐ pared with the six-membered lactone ring of the G series. AFM1 and AFM2 are hydroxylat‐ ed forms of AFB1 and AFB2 [5]. AFM1 and AFM2 are major metabolites of AFB1 and AFB2 in humans and animals and may be present in milk from animals fed on AFB1 and AFB2 contaminated feed [6, 7]. AFM1 may be also present in egg [8], corn [9] and peanut [10, 11].

crops [16]. Therefore, in order to avoid the toxicity, the levels of aflatoxins and similar toxic compounds in foodstuffs have to be monitored closely, and to be kept under control contin‐ uously. Otherwise, related health effects like acute and chronic intoxications, and even

Occurrence of Aflatoxins in Food http://dx.doi.org/10.5772/51031 145

In this review, we are presenting a report on the situation of aflatoxin contamination in food and foodstuffs such as oilseeds (peanuts, almonds, pistachios and other tree nuts), cereals (wheat, barley, rice, corn, etc), spices, milk and dairy products and other foods of animal ori‐ gin (meat, offal, eggs etc) in world. Incidence of contamination will classified as country and type of food and discussed. Also, we are reviewing the scientific literature on aflatoxins in

Oilseed crops are primarily soybeans, sunflower seed, canola, rapeseed, safflower, flaxseed, mustard seed, peanuts and cottonseed, used for the production of cooking oils, protein meals for livestock, and industrial uses. These specific oilseeds are eligible for nonrecourse loans. Other oilseed crops include castor beans and sesame. After extraction of the oil the residue is a valuable source of protein, especially for animal feeding stuffs, as in oil-seed cake or press cake. Oilseeds and their products are mainly consumed as snacks as well as

According to many reports (Table 1), peanuts are the main susceptible products for aflatoxin contamination [19-21]. Tree nuts such as almonds, walnuts, and pistachios may be contami‐ nated with aflatoxin, though at lower levels than for cottonseed and corn; however, the problem is very significant to producers because: (1) the crop has a high unit value, and (2) much of the crop is sold to European markets that enforce limits significantly lower than

For over all sanitary precaution, the European Union has enacted in 1998, very severe afla‐ toxin tolerance standards of 2 µg kg-1 AFB1 and 4 µg kg-1 total aflatoxins for nuts and cere‐ als for human consumption and this has come into effect from January, 2001. Consumers in the developed world are well aware of the carcinogenic effect of aflatoxins and will thus stay away from a product that has aflatoxin beyond the acceptance level. Exports of agricul‐ tural products particularly groundnuts and other oilseeds from developing countries have dropped considerately in recent years resulting in major economic losses to producing coun‐ tries as a result of this restriction. According to the World Bank estimate, the policy change by the European Union will reduce by 64%, imports of cereals, dried fruits, oil seeds and nuts from nine African countries namely Chad, Egypt, Gambia, Mali, Nigeria, Senegal, South Africa, Sudan and Zimbabwe and this will cost African countries about US \$670 million in trade per year. However, the new rule of the EU has been criticized as being too strin‐ gent. There is the need for mycotoxin surveillance because of its wide occurrence in conta‐

deaths, will still be an issue [17].

those in some countries [22].

minated commodities [23].

foods and how they affect animal and human health.

part of the ingredients of certain dishes in human daily diet [18].

**2. Occurrence of Aflatoxin in Oilseeds**

AFs interact with the basic metabolic pathways of the cell disrupting key enzyme process‐ es including carbohydrate and lipid metabolism and protein synthesis [12]. The health ef‐ fects of aflatoxins have been reviewed by a number of expert groups. Aflatoxins are among the most potent carcinogenic, teratogenic and mutagenic compounds in nature [13]. The In‐ ternational Agency for Research on Cancer (IARC) has concluded that naturally occurring aflatoxins are carcinogenic to humans (group 1), with a role in etiology of liver cancer, no‐ tably among subjects who are carriers of hepatitis B virus surface antigens. In experimen‐ tal animals there was sufficient evidence for carcinogenicity of naturally occurring mixtures of aflatoxins and of AFB1, AFG1 and AFM1, limited evidence for AFB2 and inadequate evi‐ dence for AFG2. The principal tumors were in the liver, although tumors were also found at other sites including the kidney and colon. AFB1 is consistently genotoxic in vitro and in vivo [3].

The Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) estimated potency val‐ ues for AFB1 from the epidemiological data. These corresponded to 0.3 cancers/year per 100,000 population per ng aflatoxin/kg body weight (b.w). per day (uncertainty range: 0.05-0.5) in hepatitis B virus antigen positive individuals and 0.01 cancers/year per 100,000 population per ng aflatoxin/kg b.w. per day (uncertainty range: 0.002-0.03) in hepatitis B vi‐ rus antigen negative individuals. AFM1 has been evaluated separately from AFB1 by the JECFA, because of its potential to be present in milk and milk products of livestock fed on aflatoxins contaminated feed [14]. The JECFA concluded that AFM1 should be presumed to induce liver cancer in rodents by a similar mechanism to AFB1, and that estimates of the po‐ tency of AFB1 can be used for determining the risk due to intake of AFM1, including those for populations with a high prevalence of carriers of hepatitis B virus. The carcinogenic po‐ tency of AFM1 was estimated to be one-tenth that of AFB1, based on a comparative study in the Fischer rat conducted by Cullen et al. [15].

Humans can be exposed to aflatoxins by the periodic consumption of contaminated food, contributing to an increase in nutritional deficiencies, immunosuppression and hepatocellu‐ lar carcinoma. AFs have a wide occurrence in different kind of matrices, such as spices, cere‐ als, oils, fruits, vegetables, milk, meat, etc. [5]. About 4.5 billion people, mostly in developing countries, are at risk of chronic exposure to aflatoxins from contaminated food crops [16]. Therefore, in order to avoid the toxicity, the levels of aflatoxins and similar toxic compounds in foodstuffs have to be monitored closely, and to be kept under control contin‐ uously. Otherwise, related health effects like acute and chronic intoxications, and even deaths, will still be an issue [17].

In this review, we are presenting a report on the situation of aflatoxin contamination in food and foodstuffs such as oilseeds (peanuts, almonds, pistachios and other tree nuts), cereals (wheat, barley, rice, corn, etc), spices, milk and dairy products and other foods of animal ori‐ gin (meat, offal, eggs etc) in world. Incidence of contamination will classified as country and type of food and discussed. Also, we are reviewing the scientific literature on aflatoxins in foods and how they affect animal and human health.
