The Effect of Heat& Cold on The L.monocytogenes in the Milk

The influence of heat and cold on the L.monocytogenes in the milk In order to know the thermal resistance of L.monocytogenesin the contaminated milk, 40gram of powder milk was dissolved in 400ml of heated water.The milk solution was sealed in 40 test tubes 10 ml in each one.these test tubes were divided into 6 groups,10test tubes in each the 1st,2nd group &5 test tubes in each the 3rd,4th,5th,6th groups,then all the test tubes were inoculated with L.monocytogenes &incubation for 24hrs at 37c.the samples of the 1st &2nd group were dipped in awater bath at tempreture 63c for 30minute &72c for 1-5.5 minute respectively.also the samples of 3rd &4th groups were dipped in awater bath at 72c for 6minute. Test tubes of 1st,3rd,5th groups were kept in 4c for variable times while samples of 4th,6th group were exposured to - 18c for 12days. The results showed no bacterial isolates immediately after heat treatment in all the milk samples of 1st.3rd &4th groups but some isolates were seen after enrichment at 4c&- 18c L.monocytogenes was isolate from all samples of 2nd,5th &6th groups. The results suugest that cold enrichment play role in repair the thermally injured cells of L.monocytogenes&these organisms surviveve thermal treatment.

Abstract licence: CC BY

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