Abstract: ‎ BACKGROUND: The extensive consumption of milk and dairy products makes these foodstuffs ‎targets for potential adulteration with financial gains for unscrupulous producers.‎ OBJECTIVES: The aim of this study was using PCR assay to detection of cow\\\'s milk in labeled ‎sheep milk, sheep yoghurt and Lighvan cheese (a traditional ripened cheese produced from sheep’s ‎milk). METHODS: The assay utilized primers targeting the mitochondrial 12s and 16s rRNA gene. ‎In this study 35 samples of sheep milk, 35 samples of sheep yoghurt and 35 samples of Lighvan ‎cheese were purchased from different supermarkets in Mashhad city with different batch numbers. ‎RESULTS:‎‏ ‏The results showed only 21 out of 105 (20%) samples contained pure sheep milk. ‎Undeclared presence of cow’s and goat’s milk was detected in 33(31.5%) and 68(65%) of total ‎‎105 samples respectively. CONCLUSIONS: It seems this PCR based analytical method is an ‎applicable technique to monitor adulteration in dairy products.‎ Key words: adulteration, milk, yoghurt, Lighvan cheese, PCR-based method

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