Probiotic Attributes Analysis – Thermal Death Point

Estimation of potential Probiotic Attributes


Thermal death point (TDP) is the temperature at which an organism is killed within 10 minutes. This test is used to check how the organism reacts to rising temperature. The enzymes of an organism function at a particular temperature. If any of these parameters changes, the growth will decrease with the death of organism. Thermal death point measure the degree of tolerance of an organism, by exposing it to an increasing temperature for a specified time.


  1. Bacterial culture
  2. Eppendorf tubes
  3. Water Bath
  4. MRS Plates


  1. Incubate the microbial culture over night in MRS Broth at 37°C.
  2. Divide 5 ml of microbial culture over 5 Eppendorf tubes.
  3. Preheat the water bath at 40°C and once it has reached at that temperature put the first Eppendorf into the warm water bath.
  4. Wait for 10 min and then take 100μL from the Eppendorf on MRS plate.
  5. Spread the culture over the plate so that the culture is equally dispensed.
  6. Repeat the same step for 50-80°C.
  7. Incubate the plates for 24-48 hours.
  8. The plate with the highest temperature and visible growth can be regarded as the TDP.
  9. Blot dry with tissue paper and examine under oil immersion. Gram-positive organisms stain blue to purple; gram-negative organisms stain pink to red.
  10. There is no need to place a coverslip on the stained smear.
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