Abstract: The effect of ciprofloxacin residue on sensory properties, acidity, texture and volatile flavor substances in S. thermophilus fermented milk was studied. The results showed that the sensory quality of the fermented milk was significantly affected by ciprofloxacin at concentrations higher than 0.4 μg/mL. The viscosity of the fermented milk revealed a reduction and more severe dehydration and shrinkage was found at ciprofloxacin concentrations higher than 0.2 μg/mL. The content of volatile components in the fermented milk obviously decreased when the ciprofloxacin concentration was 0.1 μg/mL. These findings show that ciprofloxacin residue in raw milk used for preparing fermented dairy products should be less than 0.1 μg/mL.

Key words: ciprofloxacin, fermented milk, S. thermophilus