Thermal Death Time Calculations

An in-depth discussion of TDT calculations is not possible here. Readers are referred to works such as Ref. 5. The following formula is used to calculate the D value:

where t is the heating time (corrected for the come up time) at temperature T, A is the initial number of organisms, and B is the number of survivors. Alternatively, the D value can be determined by plotting the number of survivors at several time intervals against time on semilogarithm paper. (The D value is calculated from the slope of the bestfit line.) D values determined at several temperatures are plotted on semilogarithm paper against temperature (called a phantom TDT curve), and the z value (the change in the thermal death rate with temperature) is calculated from the slope of the line. Knowing the D and z values for an organism allows the calculation of the D value at any other temperature. The F value, or the number of minutes to destroy a given number of organisms at a specific temperature, can also be calculated. The minimum health sterilizing value for a low-acid food is generally a 12D value for C. botulinum (12 times the D value determined for C. botulinum spores in the specific food); the commercial sterility value is generally 5D for C. sporogenes (PA3679) spores.

How To Have Beutiful Non Aging Skin

How To Have Beutiful Non Aging Skin

Age does a lot of things to us and most of them arent good. Sure, we may get wiser, and more knowledgeable as a result of our experiences over time, but time also takes a hefty toll on our health, and appearance.

Get My Free Ebook


Responses

  • Alessio
    How to calculate thermal death time?
    2 years ago
  • Kerstin
    How to calculate z value in thermal death curves?
    5 months ago

Post a comment