Survive time and Kill time calculation

·        survivor time, also known as a death rate,

·        microbial inactivation.

    A survivor curve, also known as a death rate curve,is a graphic representation of microbial inactivation over increased exposure to stated condition.

    

 Minimum Expected Survival Time

·        Survival Time = Not Less Than D - value x (log 10 viable spore population - 2)

Maximum Expected Kill Time

·        Kill Time = Not More Than D - value x (log 10 viable spore population + 4)

 Ex:1    

   D 121 =1.9 

  Spore population: 2.0 x 10⁶                                                                              

  Survival time =8.17               

   Kill time= 19.57

CST (calculate survival time) = (log 2.0 x 10⁶ -2) (1.9 minutes)
= log 2.0 + 6 log 10-2 x 1.9
= log 2.0 + 6 -2  x 1.9
= 0.301 - 2 x 1.9
= 4.301 x 1.9
= 8.17
CKT (calculate Kill time) = (log 2.0 x 10⁶ +4) (1.9 minutes)
= log 2.0 + 6 log 10 + 4 x 1.9
= log 2.0 +6 + 4 x 1.9
= 0.3010 + 6 +4 x 1.9
= 10.301 x 1.9
= 19.57

Ex:2

    D 121 =1.7 

    Spore population: 1.8 x 10⁵                                                                                       

    Survival time =5.5               

      Kill time = 15.7

CST (calculate survival time) = (log 1.8 x 10⁵ -2) (1.7 minutes)
= 0.25527 +5 - 2 x 1.7
= 5.2552 - 2 x 1.7
= 3.2552 x 1.7
= 5.53                                                       

CKT (calculate Kill time) = log 1.8x 10⁵ +4) (1.7 minutes)
= 0.25527 + 5 +4 x 1.7
= 9.25527 x 1.7
= 15.73