Effect of lactic cultures on Escherichia coli in ewes' milk stored at low temperatures

The behaviour of Escherichia coli in pasteurized ewes' milk inoculated with different lactic starter cultures and incubated at temperatures in the range 4-16 degrees C for 96 h was investigated. Growth temperature of lactic starter cultures before inoculation had a significant effect on inhibition of E. coli. The growth temperature of lactic starter inoculum which resulted in the highest inhibitory activity was 24 degrees C. Size of lactic starter inoculum also significantly influenced growth of E. coli, with a higher inhibition for 1% inoculum than for 0.1% or 0.3% inocula. Single cultures of Lactococcus lactis showed a stronger inhibitory activity than single cultures of Leuconostoc cremoris or Leuconostoc dextranicum. A lactic starter culture comprising Lactococcus lactis, Leuconostoc cremoris and Leuconostoc dextranicum resulted in the strongest inhibition. Stimulation of E. coli by the lactic starter cultures was frequently recorded at 4 degrees C and 8 degrees C. However, none or a very limited growth of E. coli was seen at these temperatures.