en تخصصي Special Original article Original article <p><font face="times new roman,times,serif" size="2"><b>Background:</b> Aflatoxin M₁ (AFM₁) is a toxic and carcinogenic mycotoxin which after presence in milk and dairy products such as cheese and butter could make them as contaminated food. The main objective of this study was to evaluate the concentration of AFM₁ in pasteurized and traditional cheese marketed in Southern Khorasan, from December 2011 to January 2012.<br> <b>Methods:</b> A total of 102 cheese samples (including 43 non-pasteurized traditional and 59 pasteurized cheese) were analyzed for detection of AFM1. The samples were collected ran-domly from three major cities of Southern Khorasan province, Iran. A rapid and sensitive indirect competitive Enzyme Linked Immuno Sorbent Assay (ELISA) method using monoclonal antibody was used to measure AFM₁ concentration in the samples.<br> <b>Results:</b> According to the results of this study, AFM₁ was detected in 14 (32.55%) traditional and 21 (35.59%) pasteurized cheese samples. In total, 25.42% of pasteurized and 27.90% of traditional cheese samples were contaminated at above level of the Iranian standard limits (50 ng/kg).<br> <b>Conclusion: </b>Considering high contamination level of both pasteurized and traditional cheese products in Southern Khorasan, it is recommended to establish continuous monitoring program of AFM₁ by food safety agencies in order to control the incidence of mycotoxin contamination. </font></p> Aflatoxin M1, Cheese, Iran 77 80 http://jfqhc.ssu.ac.ir/browse.php?a_code=A-10-1-31&slc_lang=en&sid=1 M. Khodadadi No Family Health and Environment Research Center, Birjand University of Medical Sciences, Birjand, Iran R. Khosravi No Family Health and Environment Research Center, Birjand University of Medical Sciences, Birjand, Iran A. Allahresani No Chemistry Faculty, Birjand University, Birjand, Iran Y. Khaksar No Shahid Sadoughi University of Medical Sciences, Yazd, Iran L. Rafati No Department of Environmental Health, Shahid Sadoughi University of Medical Sciences,Yazd, Iran B. Barikbin b_barikbin @yahoo.com Yes Chemistry Faculty, Birjand University, Birjand, Iran