Abstract: During the fermentation and storage of yoghurt, the effect of yoghurt culture on the survival and production ofthermonuclease of Staphylococcus aureus added to milk in various concentrations was observed. The end of the fermentationprocess was accompanied by a slight increase of Staphylococcus aureus. During the storage of yoghurt at 4℃ a 1～2 log reductionwas observed. No Staphylococcus aureus was detected in yoghurt produced from milk contaminated by 8.5×103cfu/mlStaphylococcus aureus after 72h of cold storage.When a concentration of 1.8×10、1.8×102cfu/ml Staphylococcus aureus cellswas used for milk contamination,the patbgen was not recovered from yoghurt during the fermentation and storage. Thethermonuclease was negative in yoghourt from milk when contaminated by 1.8×10、1.8×102cfu/ml Staphylococcus aureus;the thermonuclease was all pasitive when staphylococcus aureus were added to milk in concentration of 5.8×103、2.7×104、2.7×105、1.8×106cfu/ml respectively. The fermentation and storage of yoghurt were accompanied by the increase in lacticacid and a decrease in pH value.

Key words: Staphylococcus aureus, counts, yoghurts, thermonuclease (TNase)