GROWTH AND SURVIVAL OF PATHOGENIC E. COLI DURING CURDLING OF MILK

The presence of pathogenic serotypes of E. coli in milk and milk products causes food borne illness. Curd is prepared by fermenting milk with Lactic Acid Bacteria (LAB). Among LAB, Lactobacillus acidophilus L. delbrueckii, L. bulgaricus, Streptococcus thermophilus and Lactococcus lactis, are the main organisms used for the preparation of curd in India. Apart from producing non-specific antimicrobial substances such as lactic acid and H2O2, LAB also capable of synthesizing more specific bacteriostatic and bactericidal agents. The inhibitory effect of LAB during curdling of milk on growth of pathogenic and non-pathogenic E. coli was studied. The two E. coli strains had been found to behave differently during fermentation of milk with LAB at 37oC. Growth of E. coli 026 was reduced greatly during curdling of milk whereas inhibition of growth was not significant for E. coli 10536. Death rate of E. coli 026 in curd was found to be much higher than E. coli 10536