Background: Aflatoxin M₁ (AFM₁) is a toxic compound that could be found in milk and dairy products. AFM₁ is the principle hydroxylated derivative of aflatoxin B₁ (AFB₁), formed in liver and excreted into the milk in the mammary glands of both human and lactating animals that have been fed with AFB₁ contaminated diet. To the best of our knowledge, there is no report on stability of AFM₁ during production of Iranian traditional kashk (ITK). This study designed to assess the effect of ITK processing on AFM₁ content of cow’s milk artificially contaminated with AFM₁.

Methods: ITK making consisted of production of yogurt and strained yogurt, boiling the strained yogurt to make a curd and drying the resultant curd, according to common native procedure in Iran. AFM₁ content of initial yogurt, strained yogurt and dried kashk was determined using high performance liquid chromatography (HPLC). Statistical analyses were performed by Student’s t-test and ANOVA using the SPSS 16.0 software package program.

Results: 'The mean concentration of AFM₁ in final ITK was determined as 0.118 µg/kg which was significantly (p<0.05) lower than that of initial milk, yogurt and strained yogurt samples. Also, AFM₁ content of yogurt, strained yogurt and final ITK product was 46.12%, 6.94% and 48.24%, respectively lower than that of initial milk (p<0.05).

Conclusion: This study showed that ITK processing can effectively degrade AFM₁ presented in initial raw milk and could be useful for minimizing AFM₁ content of highly contaminated raw milk in dairy industries.