Doogh is a traditional Iranian yoghurt drink. Apart from Iran, Doogh is exported and consumed in other countries such as Armenia, Syria, Turkey, and Balkans, and to less extent in other countries of Middle East and central Asia. In present time, Doogh is a very popular and highly consumed product in Iran with a considerable increasing demand for its consumption . This study has been conducted to determine the microbiological contamination sources during production of Iranian yoghurt drink in three local dairy plant , mashhad, Iran. Samples were collected at 16 sites along the line. Total count, psychrotrophic, coliform and yeast was determined according to the Institute of Standards and Industrial Research of Iran (ISIRI ). The results showed that the hygienic quality of Iranian yoghurt drink is dependent on the quality of raw milk, the effect ive heat treatment of the milk base, the microbiological quality of added ingredients and packaging materials, the cleanliness of surfaces coming into contact with the yoghurt drink and the efficiency of the plant sterilisation.

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