Determination of aflatoxins in imported rice to Iran

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Abstract

Aflatoxins (AFs) are highly toxic and carcinogenic secondary fungal metabolites and have been detected in various food commodities including cereals. Rice were imported to Iran during March 2006–March 2007 analyzed for aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2) using immunoaffinity column and quantitated by HPLC. In this regard, 71 rice samples were collected. After dividing samples to sub-samples, AF analyses were done. Among 71 samples analyzed, AFB1 was detected in 59 samples (83% of the total). The mean of AFB1 was 1.89 ng/g for all samples (with the not detected samples taken as zero). Total AF (AFT) was detected in 59 samples (83% of the total). The mean of AFT was 2.09 ng/g for all samples. AFB1 level in two samples (2.8%) was above the maximum tolerated level (MTL) of AFB1 in Iran (5 ng/g). Regarding AFT, the mean contamination level (2.09 ng/g) was lower than MTL of AFT in rice in Iran as well as lower than maximum level of EU for AFT (4 ng/g), and only nine samples had levels above the MTL of EU in AFT.

Introduction

The aflatoxins (AFs) are a group of toxic and carcinogenic polyketide secondary metabolites, which are produced by strains of Aspergillus flavus, Aspergillus parasiticus, Aspergillus nomius and Aspergillus pseudotamarii (Payne, 1998). The International Agency for Research on Cancer (IARC) has classified aflatoxin B1 (AFB1) as a Group I carcinogen, primarily affecting liver (IARC, 1993). AF is found as contaminants in various agricultural commodities such as cereals, tree nuts, groundnut and cottonseed (Pittet, 1998).

The knowledge that mycotoxins can have serious effects on humans and animals has led many countries to establish maximum tolerated level (MTL) on mycotoxins in foodstuffs and feedstuffs in the last decades to safeguard the health of humans, as well as the economical interests of producers and traders. Currently, worldwide range of limits for AFB1 and total (AFT) are 1–20 ng/g and 0–35 ng/g, respectively (FAO, 2004). Rice is one of the most important crops in the world. In 2002/2003, 40,86,61,000 metric tons were consumed (US Department of Agriculture (USDA), Foreign Agricultural Service (FAS), August 2002).

In this study, incidence of AF in imported rice from several ports of Iran was investigated.

Section snippets

Chemicals

AF standards for the experiments were purchased from Sigma Chemical Company, USA. A stock standard solution of AF at 10,000 μg/ml in methanol was prepared and kept wrapped in aluminum foil at −20 °C; AF working solutions were prepared by dilution in the same solvent and stored in glass-stoppered tubes at 0 °C. All solvents used for the experiments (methanol, acetonitrile and deionized water) were HPLC grade. Deionized water was obtained using a Mili-Q water purification system (Millipore, Bedford,

Results and discussion

The average recoveries and relative standard deviation of the analytical methods applied for AFB1, AFB2, AFG1 and AFG2 in rice were investigated. The results are shown in Table 1. Both recoveries and SD of AF were in the acceptable range (70–110%). The results of participation of labs in the proficiency testing of FAPAS were satisfactory, since almost all of Z-scores of individual AF as well as AFT were in the acceptable range (Z-score between −2 and +2). These results indicated good accuracy

Safety

AF are carcinogens and care should be exercised to avoid personal exposure and potential risk of contamination. All handling of pure compounds were done in the fume hood with protective gear such as safety glasses, gloves, laboratory coat and a disposable face mask.

The glasswares were washed with hypochlorite and dilute acid before re-using and the waste materials treated with hypochlorite before disposal.

Conflict of interest

The authors declare that there are no conflicts of interest.

References (8)

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    Worldwide Regulations for Mycotoxins in Food and Feed in 2003. FAO Food and Nutrition Paper No. 81

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There are more references available in the full text version of this article.

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